PI3K Pathway Targets in Triple-Negative Breast Cancers

Published OnlineFirst June 7, 2013; DOI: 10.1158/1078-0432.CCR-12-0274

Clinical Cancer Molecular Pathways Research

Molecular Pathways: PI3K Pathway Targets in Triple-Negative Breast Cancers

Vallerie Gordon1,2 and Shantanu Banerji1,2,3

Abstract The triple-negative breast cancer (TNBC) subtype, defined clinically by the lack of estrogen, progesterone, and Her2 receptor expression, accounts for 10% to 15% of annual breast cancer diagnoses. Currently, limited therapeutic options have shown clinical benefit beyond cytotoxic chemotherapy. Defining this clinical cohort and identifying subtype-specific molecular targets remain critical for new therapeutic development. The current era of high-throughput molecular analysis has revealed new insights into these targets and confirmed the phosphoinositide 3-kinase (PI3K) as a key player in pathogenesis. The improved knowledge of the molecular basis of TNBC in parallel with efforts to develop new PI3K pathway–specific inhibitors may finally produce the therapeutic breakthrough that is desperately needed. Clin Cancer Res; 19(14); 1–7. Ó2013 AACR.

Disclosure of Potential Conflicts of Interest No potential conflicts of interest were disclosed. CME Staff Planners' Disclosures The members of the planning committee have no real or apparent conflict of interest to disclose. Learning Objectives Upon completion of this activity, the participant should have a better understanding of the role of the PI3K signaling pathway in breast cancer, particularly triple-negative breast cancer, and the potential new inhibitors under development against targets in the PI3K pathway. Acknowledgment of Financial or Other Support This activity does not receive commercial support.

Background ing the p110 subunit to catalyze 4,5-phosphoinositide The complex network of PI3K signaling in breast cancer (PIP2) phosphorylation to 3,4,5-phosphoinositide (PIP3; Phosphoinositide 3-kinase (PI3K) is part of a larger ref. 3). Some RTKs require the presence of adaptor mole- family of lipid kinases that phosphorylate the 3-hydroxyl cules (e.g., IRS1) to interact with p85. The tumor suppres- group of phosphoinositides involved in regulation of sors PTEN and INPP4B in turn hydrolyze PIP3 and PIP2, diverse cellular processes, including cell proliferation, sur- respectively, directly opposing PI3K activity (4, 5). Onco- PIK3CA vival, and migration (1). Three classes are known to exist genic mutations in have been identified in many although Class I PI3K are the most frequently mutated in cancers, including all subtypes of breast cancer (6). The cancer (2). The PI3K are heterodimeric proteins consisting majority of these mutations are within the helical (E545K of a catalytic (p110) subunit and regulatory (p85) subunit and E542K) and kinase (H1047R) domains and result in (1). Figure 1 summarizes some of the key relationships constitutive activation of the kinase (7). Mutations in PIK3CA PTEN involved in PI3K signaling via AKT and mTOR signaling are also mutually exclusive of loss in breast mediators. Activation of a membrane-associated receptor tumors (8). The second messenger molecule PIP3 facilitates tyrosine kinase (RTK) by ligand results in the recruitment the colocalization of the serine/threonine kinases PDK1 of the p85 subunit, causing a conformation change allow- and AKT to the cell membrane via their plekstrin homology (PH-) domains, leading to downstream PI3K pathway activation (9). PIK3CA mutant cells may contribute to tumor Authors' Affiliations: 1Department of Medical Oncology, CancerCare Man- formation by both AKT-dependent and AKT-independent 2 itoba; Department of Internal Medicine, Faculty of Medicine, University of mechanisms (10). Manitoba; and 3Manitoba Institute of Cell Biology, Winnipeg, Manitoba, Canada Three AKT isoforms are known to exist (AKT-1, -2, -3), Corresponding Author: Shantanu Banerji, CancerCare Manitoba, ON5050-675 McDermot Avenue, Winnipeg, MB R3E 0V9, Manitoba, and each has very distinctive roles depending on the Canada. Phone: 204-787-8559; Fax: 204-786-0196; E-mail: specific cell lineage. For a more complete review of [email protected] AKT isoforms, please refer to the article by Toker (11). doi: 10.1158/1078-0432.CCR-12-0274 AKT1 mutations have only been identified in estrogen Ó2013 American Association for Cancer Research. receptor (ER)-positive breast tumors, whereas AKT3 is the

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Receptor tyrosine kinase: e.g., EGFR, IGFR, PDGFR, KIT, FGFR

BKM120 GDC-0941 PIP2 INPP4B

PI3 kinase PDK1 IRS1 p85 p110 PTEN

RAS PIP3 AKT BEZ235 TSC1/2 RAF mTOR

MK2206

MAPK mTORC1 mTORC2

Everolimus Temsirolimus S6K 4EBP1

Cell proliferation, survival, and migration

Figure 1. PI3K signaling through AKT in breast cancer, including multiple clinically relevant feedback loops. Solid lines represent interactions with stimulatory effect, whereas dashed lines represent inhibitory effects. Common drugs that inhibit speciﬁc members of the signaling pathway are shown in purple boxes. AKT, v-akt murine thymoma viral oncogene homolog; CD117 (KIT); 4EBP1, eukaryotic translation initiation factor 4E binding protein 1; INPP4B, inositol polyphosphate-4-phosphatase, type II; p85, phosphoinositide-3-kinase regulatory subunit; p110 a.k.a. PIK3CA, phosphoinositide-3-kinase catalytic subunit; PDK, phosphoinositide-dependent kinase 1; RAF, v-raf murine sarcoma viral oncogene homolog; RAS, v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog; S6K, ribosomal protein S6 kinase.

dominant isoform expressed in ER-negative tumors (12, sion/amplification (20, 21). This cohort accounts for 10% 13). AKT activation, either by upstream signals or muta- to 15% of annual breast cancer diagnoses in a general tion, alters multiple downstream proteins, including the population and typically presents in younger patients, relief of mTOR repression by the tuberous sclerosis com- with more poorly differentiated tumors compared with plex (TSC1/2) proteins (14). Activated mTOR forms two receptor-positive cases (20). Patients with TNBC are also unique complexes with other proteins (TORC1 and more likely to experience a recurrence within the first TORC2; 15). TORC2 containing rictor stimulates further 3 years of diagnosis, usually with distant visceral meta- AKT activation (16), whereas TORC1 containing raptor stasis, leading to an increased likelihood of breast cancer– mediates growth-stimulatory effects of mTOR. Multiple specific mortality (21, 22). feedback mechanisms exist within the PI3K/AKT/mTOR Defining TNBC remains a challenge due to significant signaling cascade that can complicate therapy. Among disease heterogeneity. The classic "triple receptor-negative" these are the activation of PI3K and mitogen-activated phenotype shows significant overlap with, but is not syn- protein kinase (MAPK) signaling pathways in the setting onymous with, newer breast cancer subtypes defined by of mTOR-specific inhibitors caused by the relief of S6K- gene expression–based classification methods. Perou and mediated repression of IRS1 (17, 18), and reactivation of colleagues have described four reproducible intrinsic gene RTK expression with AKT inhibition (19). expression subtypes: luminal A, luminal B, Her2-enriched, and basal like (23). The luminal subtypes mainly represent Defining the triple-negative breast cancer cohort ER-expressing epithelial cells, whereas the Her2-enriched Triple-negative breast cancer (TNBC) is defined clini- subtype reflects HER2 gene activation (23). The basal-like cally by the lack of expression of ERs and progesterone subgroup shows the greatest overlap with TNBC tumors and receptors and the absence of human EGF2 (Her2) expres- is associated with the worst prognosis of all the intrinsic

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subtypes. A subgroup of TNBC without basal markers has Genomic analysis of breast cancer reveals PI3K recently been identified. This "claudin-low" group seems to pathway aberrations be enriched for mesenchymal and stem cell markers (24). Defining the genetic heterogeneity of breast cancer has Lehmann and colleagues confirmed the complexity of these been proposed as key to understanding the pathogenesis of tumors at the expression level by showing that TNBC the disease and to identify new targets to guide therapy into tumors can be further subclassified into six different expres- the future. Over the past year, several international collab- sion-based cohorts (25). The majority of these cohorts share orative groups have reported on high-throughput, genome- characteristics of the intrinsic basal-like subtype except a scale and cross-platform analyses covering the spectrum of luminal androgen receptor (LAR) cohort of TNBC whose breast cancer expression subtypes (13, 27, 34–36). These expression profile shows similarity to intrinsic luminal studies confirmed that the clinical and molecular hetero- subtypes (25). geneity of breast cancer is reflected in the cancer genome. The overlap between the clinical immunohistochemistry However, distinct patterns of genomic alterations have been (IHC) and molecular gene expression cohorts often leads to teased from the data. The most common genes with somatic the labels TNBC and basal like used interchangeably, which mutations in breast cancer include TP53, PIK3CA, GATA3, is inappropriate given the heterogeneity between these MAP3K1, MLL3, CDH1, RB1, MAP2K4, RUNX1, PTEN, molecular defined cohorts (26). An integrated genomic AKT1, and CBFB (13, 27, 34), the majority of which have analysis of 466 breast tumors revealed that 80% of TNBCs been previously described in less expansive genomic stud- were classified as basal like, whereas other common sub- ies. Only TP53 and PIK3CA mutations are seen at mutation types, mainly the Her2-enriched, represented the remainder frequencies across expression subtypes exceeding 10% of (27). The gene expression–based basal-like subtype seems samples. The remaining mutations, despite occurring at to be more reproducible compared with the IHC-defined much lower frequencies, had some interesting characteris- TNBC cohort and has been the focus of further genomic tics. For example, mutations in MAP3K1, MAP2K4, GATA3, exploration as detailed below. CDH1, AKT1 , RUNX1, and CBFB occurred almost exclu- sively in luminal and Her2-enriched subtypes associated Current treatment of triple-negative breast cancers with hormone receptor–positive disease (13, 27). Also, Despite lower survival, triple-negative tumors paradoxi- most mutations in genes with known connections within cally show an increased sensitivity to neoadjuvant cytotoxic a cellular pathway (e.g., PIK3CA/AKT1, MAP3K1/MAP2K4, chemotherapy compared with non-TNBC cases (pathologic or RUNX1/CBFB) tended to be mutually exclusive, suggest- complete response rates 22% vs. 11%, respectively; P ¼ ing that pathway disruption rather than the individual gene 0.034; ref. 22). These higher responses are seen with both mutation may be more important (13, 27). anthracycline and taxane-based regimens used to treat Relative to other expression subtypes, genomic altera- breast cancer and may reflect the higher cell proliferation tions in the basal-like breast cancers appeared to be much rates of these tumors (22, 28). In patients who harbor more homogeneous. In the study by The Cancer Genome germline mutations in the BRCA1 gene, greater responses Atlas, 80% of the 98 basal-like tumors harbored muta- have also been observed with the DNA cross-linking agent tions in TP53 (27). Most of these mutations were non- cisplatin (29, 30). Patients also seem to benefit from cyto- sense or frame shift mutations believed to be more toxic therapy in the adjuvant and metastatic settings, deleterious to TP53 function. An integrated analysis of although in the latter group, responses are short lived. The datasets suggests that TP53 function is lost in all basal-like lack of common molecular targets means that less toxic cancers (27). Furthermore, contributing to abnormalities hormonal and targeted therapies that are used for non- in cell-cycle regulation and DNA repair were loss of genes TNBC tumors are not available for the treatment of this RB1, BRCA1, BRCA2,andATM (27, 36). These findings breast cancer subtype. are consistent with the observation that basal-like tumors The observation of frequent TP53, BRCA1,andBRCA2 show the greatest genomic instability of all subgroups mutations in TNBC led to the hypothesis that DNA repair, (13, 27, 36) and provide a partial explanation for why specifically the homologous recombination mechanism these tumors are more sensitive to DNA-damaging agents. used to repair double-stranded DNA breaks, was defective Interestingly, the basal-like expression subtype also had in these tumors. Cells defective in homologous recom- the highest activation of downstream members of the PI3K bination can become dependent on the base excision signaling pathway as determined by both gene expression repair pathway mediated by PARP for DNA repair (31). levels and proteomic arrays (27). Genomic aberrations PARP inhibition produces a synthetic lethal effect in the observed in the PI3K pathway in basal-like tumors include presence of BRCA1/2 mutations resulting in further chro- loss/mutation of PTEN, loss of INPP4B, amplification/ mosomal instability, cell-cycle arrest, and apoptosis (31). mutation of PIK3CA (the gene encoding the p110 catalytic Early phase I and II clinical trials with PARP inhibitors subunit of the PI3K), and activating translocations involv- were encouraging (32, 33), but subsequent phase III ing the genes MAGI3 (a scaffolding protein required for studies were less convincing, and the future development PTEN activity) and AKT3 (13, 27). The PTEN and PIK3CA of these agents remains unclear. Newer targets for therapy mutations occur early in breast tumor initiation and seem to for the TNBC cohort are therefore desperately needed in be present in dominant tumor clones (35, 37). The PIK3CA the clinical setting. and PTEN mutations in TNBC tumors seem to be more

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common in the Pietenpol mesenchymal-like and LAR the preclinical setting, tumors with basal-like expression are expression subtypes (25). more sensitive to everolimus inhibition (41). Several trials with mTOR inhibitors alone or in combination with cyto- Clinical–Translational Advances toxic or targeted therapies are currently accruing (Table 1). Emergence of several PI3K pathway inhibitors PI3K inhibitors related to wortmannin are relatively The presence of multiple mediators within the PI3K new to the clinical scene. First-generation inhibitors like signaling pathway means that there are several opportu- BKM120 inhibit all class I PI3K but have no activity against nities to drug-specific targets to achieve cell arrest and mTOR. A phase I clinical trial in patients with a variety of limit toxicity of therapy. Multiple inhibitors have emerged cancers showed one confirmed partial response to this over the past decade and have been the focus of clinical agent in a patient with TNBC. The most common toxicities trials. Table 1 lists some ongoing clinical trials testing the reported with this agent have been rash, hyperglycemia, use of PI3K pathway inhibitors in breast cancer cohorts that mood alteration, epigastralgia, nausea, fatigue, mucositis, would include patients with TNBC. and pruritis (42). Other related compounds, such as BAY The first drugs to enter clinical trials were the mTOR 80-6946, GDC-0941, PX-866, and XL147, have been eval- inhibitors rapamycin and its analogues. Temsirolimus has uated in phase I trials and have a similar toxicity profile to shown only modest activity in unselected patients with that of BKM120 (43–46). metastatic breast cancer (38). Everolimus has shown clin- Newer dual inhibitors targeting both PI3K and mTOR ical benefit in 34% of trastuzumab-resistant patients treated have arrived in the clinic. Agents like BEZ235, GDC-0980, with a combination of everolimus and trastuzumab and has GSK458, SF1126, and XL765 have all shown evidence also shown significant improvement in progression-free of tolerability and target inhibition although specific survival in combination with aromatase inhibition in pre- responses in breast tumors have yet to be seen (47–51). viously resistant hormone receptor–positive patients (39, The side effects of the dual inhibitors overlap those seen 40). Common adverse effects of these therapies include with PI3K and mTOR-specific agents. TNBC cell lines hav- mucositis, rash, nausea, diarrhea, and hyperglycemia, the ing mesenchymal-like or LAR expression profiles with fre- latter likely a result of PI3K signaling also being important quent PIK3CA mutations and PTEN loss appear more for insulin sensitization. Clinical trials with mTOR-specific sensitive to dual inhibitors like BEZ235 compared with inhibitors in TNBC have not yet been reported although in other TNBC expression subtypes (25).

Table 1. Ongoing clinical trials with PI3K pathway inhibitors that include a TNBC cohort (clinicaltrials.gov)

Target Study drugs Design Na Breast subtype Identiﬁer mTOR Inhibitors Temsirolimus þ cisplatin/erlotinib Phase I 18 MBC TNBC NCT00998036 Temsirolimus þ peg-liposomal Phase I 30 MBC NCT00982631 doxorubicin Temsirolimus þ neratinib Phase I/II 65 MBC TNBC or Her2þ NCT01111825 Temsirolimus þ IMC-A12 Phase I/II 68 MBC NCT00699491 Everolimus þ abraxane Phase I/II 72 MBC Her2 NCT00934895 Everolimus þ lapatinib Phase II 43 MBC TNBC NCT01272141 Everolimus þ FEC/paclitaxel Phase II 62 Neoadjuvant stage II–III TNBC NCT00499603 Everolimus Phase II 50 Neoadjuvant stage I–III NCT01088893 after chemotherapy Everolimus þ cisplatin/paclitaxel Phase II 120 Neoadjuvant stage II–III TNBC NCT00930930 Pan PI3K GDC-0941 þ paclitaxel/ Phase I 24 Locally recurrent or MBC NCT00960960 inhibitors bevacizumab BKM120 þ olaparib Phase I 56 TNBC or high-grade serous NCT01623349 ovarian cancer BKM120 Phase II 50 MBC TNBC NCT01629615 Dual PI3K þ BEZ235 þ paclitaxel Phase I/II 230 MBC Her2 NCT01495247 mTOR inhibitors AKT Inhibitors MK2206 Phase II 30 Neoadjuvant stage I–III NCT01319539 MK2206 Phase II 40 MBC with PIK3CA mutation NCT01277757 or PTEN loss

NOTE: This list is restricted to currently recruiting trials. Abbreviations: FEC, 5-ﬂuorouracil, etoposide, and cyclophosphamide; MBC, metastatic breast cancer. aN represents the goal for recruitment.

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Inhibitors of AKT add to the spectrum of drugs targeting Answers to these questions lie only in carefully planned the PI3K signaling pathway. Allosteric inhibitors that bind and executed clinical trials. to the PH-domain of AKT like MK2206 may have utility in cases of PTEN loss or PIK3CA mutation where the protein Challenges going forward conformation of AKT remains intact (52). However, AKT- Intra- and intertumor heterogeneity continues to be a kinase domain inhibitors related to GSK690693 may have a significant challenge in the era of targeted therapy devel- greater role when the PH-domain itself is disrupted such as opment. Target discovery and routine identification in with the common E17K AKT1 mutations and the reported clinical samples are thus critical elements to modern cancer AKT3 fusion (13). care. The complexity of TNBC at the clinical and genetic levels illustrates that no single treatment approach will Combination therapy holds the key for TNBC produce universal benefit in this disease beyond what has Use of PI3K pathway inhibitors as single-agent therapies already been accomplished with broad-spectrum cytotoxic has proved minimally effective in some diseases. As shown agents. Therapies tied to specific biomarkers, along with the in Fig. 1, the complexity of the PI3K pathway with multiple more rational use of targeted therapies, remains the key to feedback mechanisms explains some of the drug resistance. improving clinical outcomes for patients with TNBC. Combination drug therapies that simultaneously target Inhibitors specific to components of the PI3K pathway these escape mechanisms will likely lead to the greatest combined with inhibition of other proliferation pathway clinical success. mTOR inhibition combined with either targets will likely yield the best results. Critical to the use of antiestrogen or anti-Her2 therapies has already shown these drugs are tools to accurately and rapidly identify success in clinical trials (38–40). Numerous other examples patients with the specific molecular biomarker that predicts of preclinical models of success have been shown in TNBCs. response to the chosen therapy. Many of these tools, includ- BRCA1-deficient cell lines treated with a PARP inhibitor ing gene expression arrays and next-generation sequencing followed sequentially by dual PI3K/mTOR inhibitor instruments, are starting to be available through clinic LY294002 showed the greatest inhibition of growth com- laboratories, but more widespread deployment of these pared with either drug alone (53). Similarly, primary breast methods will be needed in the future. To parallel these tumor xenografts treated with BKM120 are sensitized to efforts, individuals associated with the diagnosis and treat- PARP inhibition (54). However, even resistance to this ment of TNBC, and cancer in general, need to be more combination was observed in some TNBC xenografts, dynamic so that appropriate therapies can be initiated at the which could only be overcome with the addition of the optimal time for individual patients. MAP–ERK kinase inhibitor AZD6244 (54). Similar preclinical TNBC models have also shown the synergistic effect of Authors' Contributions combining EGF receptor (EGFR) and mTOR inhibition Conception and design: S. Banerji Development of methodology: S. Banerji (55). These observations still need to be tested in the clinical Writing, review, and/or revision of the manuscript: V. Gordon, S. Banerji setting. Targeted monotherapy against RTKs EGFR, fibro- blast growth factor receptor (FGFR), and insulin-like growth Acknowledgments factor I receptor (IGF-1R) have shown only limited success The authors apologize to authors whose work has contributed to advance- ments in this field but could not be cited because of restrictions in the number in TNBC to date. It is conceivable that with either a more of references. biomarker-driven therapeutic approach or combined with PI3K inhibitors, further therapeutic potential can be Grant Support achieved (56–58). Although all these combinatorial treat- This work was supported by a CancerCare Manitoba Foundation start-up ments have theoretical merit, these approaches are often grant awarded to S. Banerji. limited by the side effect profiles of each drug and whether Received October 22, 2012; revised May 8, 2013; accepted May 10, 2013; the patient can tolerate the combined toxicity profile. published OnlineFirst June 7, 2013.

References 1. Fruman DA, Meyers RE, Cantley LC. Phosphoinositide kinases. Annu 6. Kang S, Bader AG, Vogt PK. Phosphatidylinositol 3-kinase mutations Rev Biochem 1998;67:481–507. identiﬁed in human cancer are oncogenic. Proc Natl Acad Sci U S A 2. Samuels Y, Ericson K. Oncogenic PI3K and its role in cancer. Curr Opin 2005;102:802–7. Oncol 2006;18:77–82. 7. Samuels Y. High frequency of mutations of the PIK3CA gene in human 3. Luo J, Cantley LC. The negative regulation of phosphoinositide 3- cancers. Science 2004;304:554. kinase signaling by p85 and its implication in cancer. Cell Cycle 8. Saal LH. PIK3CA mutations correlate with hormone receptors, node 2005;4:1309–12. metastasis, and ERBB2, and are mutually exclusive with PTEN loss in 4. Gewinner C, Wang ZC, Richardson A, Teruya-Feldstein J, Etemad- human breast carcinoma. Cancer Res 2005;65:2554–9. moghadam D, Bowtell D, et al. Evidence that inositol polyphosphate 4- 9. Dillon RL, White DE, Muller WJ. The phosphatidyl inositol 3-kinase phosphatase type II is a tumor suppressor that inhibits PI3K signaling. signaling network: implications for human breast cancer. Oncogene Cancer Cell 2009;16:115–25. 2007;26:1338–45. 5. Li J. PTEN, a putative protein tyrosine phosphatase gene mutated in 10. Vasudevan KM, Barbie DA, Davies MA, Rabinovsky R, McNear CJ, Kim human brain, breast, and prostate cancer. Science 1997;275: JJ, et al. AKT-independent signaling downstream of oncogenic 1943–7. PIK3CA mutations in human cancer. Cancer Cell 2009;16:21–32.

www.aacrjournals.org Clin Cancer Res; 19(14) July 15, 2013 OF5

Gordon and Banerji

11. Toker A. Achieving specificity in Akt signaling in cancer. Adv Biol Regul with BRCA1 or BRCA2 mutations and advanced breast cancer: a 2012;52:78–87. proof-of-concept trial. Lancet 2010;376:235–44. 12. Nakatani K, Thompson DA, Barthel A, Sakaue H, Liu W, Weigel RJ, 34. Stephens PJ, Tarpey PS, Davies H, Van Loo P, Greenman C, Wedge et al. Up-regulation of Akt3 in estrogen receptor-deficient breast DC, et al. The landscape of cancer genes and mutational processes in cancers and androgen-independent prostate cancer lines.J Biol Chem breast cancer. Nature 2012;486:400–4. 1999;274:21528–32. 35. Shah SP, Roth A, Goya R, Oloumi A, Ha G, Zhao Y, et al. The clonal and 13. Banerji S, Cibulskis K, Rangel-Escareno C, Brown KK, Carter SL, mutational evolution spectrum of primary triple-negative breast can- Frederick AM, et al. Sequence analysis of mutations and translocations cers. Nature 2012;486:395–9. across breast cancer subtypes. Nature 2012;486:405–9. 36. Curtis C, Shah SP, Chin S-F, Turashvili G, Rueda OM, Dunning MJ, 14. Inoki K, Li Y, Zhu T, Wu J, Guan K-L. TSC2 is phosphorylated and et al. The genomic and transcriptomic architecture of 2,000 breast inhibited by Akt and suppresses mTOR signalling. Nat Cell Biol tumours reveals novel subgroups. Nature 2012;486:346–52. 2002;4:648–57. 37. Miron A, Varadi M, Carrasco D, Li H, Luongo L, Kim HJ, et al. PIK3CA 15. Wullschleger S, Loewith R, Hall MN. TOR signaling in growth and mutations in in situ and invasive breast carcinomas. Cancer Res metabolism. Cell 2006;124:471–84. 2010;70:5674–8. 16. Sarbassov DD. Phosphorylation and regulation of Akt/PKB by the 38. Chan S, Scheulen ME, Johnston S, Mross K, Cardoso F, Dittrich C, Rictor-mTOR complex. Science 2005;307:1098–101. et al. Phase II study of temsirolimus (CCI-779), a novel inhibitor of 17. O'Reilly KE. mTOR inhibition induces upstream receptor tyrosine mTOR, in heavily pretreated patients with locally advanced or meta- kinase signaling and activates Akt. Cancer Res 2006;66:1500–8. static breast cancer. J Clin Oncol 2005;23:5314–22. 18. Carracedo A, Ma L, Teruya-Feldstein J, Rojo F, Salmena L, Alimonti A, 39. Morrow PK, Wulf GM, Ensor J, Booser DJ, Moore JA, Flores PR, et al. et al. Inhibition of mTORC1 leads to MAPK pathway activation through Phase I/II study of trastuzumab in combination with everolimus a PI3K-dependent feedback loop in human cancer. J Clin Invest (RAD001) in patients with HER2-overexpressing metastatic breast 2008;118:3065–74. cancer who progressed on trastuzumab-based therapy. J Clin Oncol 19. Chandarlapaty S, Sawai A, Scaltriti M, Rodrik-Outmezguine V, Grbo- 2011;29:3126–32. vic-Huezo O, Serra V, et al. AKT inhibition relieves feedback suppres- 40. Baselga J, Campone M, Piccart M, Burris HA, Rugo HS, Sahmoud T, sion of receptor tyrosine kinase expression and activity. Cancer Cell et al. Everolimus in postmenopausal hormone-receptor-positive 2011;19:58–71. advanced breast cancer. N Engl J Med 2012;366:520–9. 20. Bauer KR, Brown M, Cress RD, Parise CA, Caggiano V. Descriptive 41. Yunokawa M, Koizumi F, Kitamura Y, Katanasaka Y, Okamoto N, analysis of estrogen receptor (ER)-negative, progesterone receptor Kodaira M, et al. Efficacy of everolimus, a novel mTOR inhibitor, against (PR)-negative, and HER2-negative invasive breast cancer, the so- basal-like triple-negative breast cancer cells. Cancer Sci 2012;103: called triple-negative phenotype. Cancer 2007;109:1721–8. 1665–71. 21. Dent R, Trudeau M, Pritchard KI, Hanna WM, Kahn HK, Sawka CA, 42. Bendell JC, Rodon J, Burris HA, de Jonge M, Verweij J, Birle D, et al. et al. Triple-negative breast cancer: clinical features and patterns of Phase I, dose-escalation study of BKM120, an oral pan-Class I PI3K recurrence. Clin Cancer Res 2007;13:4429–34. inhibitor, in patients with advanced solid tumors. J Clin Oncol 22. Liedtke C, Mazouni C, Hess KR, Andre F, Tordai A, Mejia JA, et al. 2012;30:282–90. Response to neoadjuvant therapy and long-term survival in patients 43. Edelman G, Bedell C, Shapiro G, Pandya SS, Kwak EL, Scheffold C, with triple-negative breast cancer. J Clin Oncol 2008;26:1275–81. et al. A phase I dose-escalation study of XL147 (SAR245408), a PI3K 23. Perou CM, Sørlie T, Eisen MB, van de Rijn M, Jeffrey SS, Rees CA, et al. inhibitor administered orally to patients (pts) with advanced malignan- Molecular portraits of human breast tumours. Nature 2000;406: cies. J Clin Oncol 28:15s, 2010 (suppl; abstr 3004). 747–52. 44. Jimeno A, Herbst RS, Falchook GS, Messersmith WA, Hecker S, 24. Lim E, Vaillant F, Wu D, Forrest NC, Pal B, Hart AH, et al. Aberrant Peterson S, et al. Final results from a phase I, dose-escalation study luminal progenitors as the candidate target population for basal tumor of PX-866, an irreversible, pan-isoform inhibitor of PI3 kinase. J Clin development in BRCA1 mutation carriers. Nat Med 2009;15:907–13. Oncol 28:15s, 2010 (suppl; abstr 3089). 25. Lehmann BD, Bauer JA, Chen X, Sanders ME, Chakravarthy AB, Shyr 45. Patnaik A, Appleman LJ, Mountz JM, Ramanathan RK, Beeram M, Y, et al. Identification of human triple-negative breast cancer subtypes Tolcher AW, et al. A first-in-human phase I study of intravenous PI3K and preclinical models for selection of targeted therapies. J Clin Invest inhibitor BAY 80-6946 in patients with advanced solid tumors: results 2011;121:2750–67. of dose-escalation phase. J Clin Oncol 29, 2011 (suppl; abstr 3035). 26. Rakha EA, Ellis IO. Triple-negative/basal-like breast cancer: review. 46. Von Hoff DD, LoRusso P, Demetri GD, Weiss GJ, Shapiro G, Rama- Pathology 2009;41:40–7. nathan RK, et al. A phase I dose-escalation study to evaluate GDC- 27. Cancer Genome Atlas Network. Comprehensive molecular portraits of 0941, a pan-PI3K inhibitor, administered QD or BID in patients with human breast tumours. Nature 2012;490:61–70. advanced or metastatic solid tumors. J Clin Oncol 29, 2011 (suppl; 28. Rouzier R, Perou CM, Symmans WF, Ibrahim N, Cristofanilli M, abstr 3052). Anderson K, et al.. Breast cancer molecular subtypes respond differ- 47. Brana I, LoRusso P, Baselga J, Heath EI, Patnaik A, Gendreau S, et al. A ently to preoperative chemotherapy. Clin Cancer Res 5005;11: phase I dose-escalation study of the safety, pharmacokinetics (PK), 5678–85. and pharmacodynamics of XL765 (SAR245409), a PI3K/TORC1/ 29. Byrski T, Gronwald J, Huzarski T, Grzybowska E, Budryk M, Stawicka TORC2 inhibitor administered orally to patients (pts) with advanced M, et al. Pathologic complete response rates in young women with malignancies. J Clin Oncol 28:15s, 2010 (suppl; abstr 3030). BRCA1-positive breast cancers after neoadjuvant chemotherapy. 48. Mahadevan D, Chiorean EG, Harris W, Von Hoff DD, Younger A, J Clin Oncol 2010;28:375–9. Rensvold DM, et al. Phase I study of the multikinase prodrug SF1126 30. Silver DP, Richardson AL, Eklund AC, Wang ZC, Szallasi Z, Li Q, et al. in solid tumors and B-cell malignancies. J Clin Oncol 29, 2011 (suppl; Efficacy of neoadjuvant cisplatin in triple-negative breast cancer. J Clin abstr 3015). Oncol 2010;28:1145–53. 49. Munster PN, van der Noll R, Voest EE, Dees EC, Tan AR, Specht JM, 31. Farmer H, McCabe N, Lord CJ, Tutt ANJ, Johnson DA, Richardson TB, et al. Phase I first-in-human study of the PI3 kinase inhibitor et al. Targeting the DNA repair defect in BRCA mutant cells as a GSK2126458 (GSK458) in patients with advanced solid tumors (study therapeutic strategy. Nature 2005;434:917–21. P3K112826). J Clin Oncol 29, 2011 (suppl; abstr 3018). 32. O'Shaughnessy J, Osborne C, Pippen JE, Yoffe M, Patt D, Rocha C, 50. Peyton JD, Rodon Ahnert J, Burris H, Britten C, Chen LC, Tabernero J, et al. Iniparib plus chemotherapy in metastatic triple-negative breast et al. A dose-escalation study with the novel formulation of the oral cancer. N Engl J Med 2011;364:205–14. pan-class I PI3K inhibitor BEZ235, solid dispersion system (SDS) 33. Tutt A, Robson M, Garber JE, Domchek SM, Audeh MW, Weitzel JN, sachet, in patients with advanced solid tumors. J Clin Oncol 29, et al. Oral poly(ADP-ribose) polymerase inhibitor olaparib in patients 2011 (suppl; abstr 3066).

OF6 Clin Cancer Res; 19(14) July 15, 2013 Clinical Cancer Research

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51. Wagner AJ, Bendell JC, Dolly S, Morgan JA, Ware JA, Fredrickson J, 55. Liu T, Yacoub R, Taliaferro-Smith LD, Sun SY, Graham TR, Dolan R, et al. A first-in-human phase I study to evaluate GDC-0980, an oral et al. Combinatorial effects of lapatinib and rapamycin in triple-neg- PI3K/mTOR inhibitor, administered QD in patients with advanced solid ative breast cancer cells. Mol Cancer Ther 2011;10:1460–9. tumors. J Clin Oncol 28:15s, 2010 (suppl; abstr 3079). 56. Carey LA, Rugo HS, Marcom PK, Mayer EL, Esteva FJ, Ma CX, et al. 52. Yap TA, Garrett MD, Walton MI, Raynaud F, de Bono JS, Workman P. TBCRC 001: randomized phase II study of cetuximab in combination Targeting the PI3K–AKT–mTOR pathway: progress, pitfalls, and pro- with carboplatin in stage IV triple-negative breast cancer. J Clin Oncol mises. Curr Opin Pharmacol 2008;8:393–412. 2012;30:2615–23. 53. Kimbung S, Biskup E, Johansson I, Aaltonen K, Ottosson-Wadlund A, 57. Litzenburger BC, Creighton CJ, Tsimelzon A, Chan BT, Hilsenbeck SG, Gruvberger-Saal S, et al. Co-targeting of the PI3K pathway improves Wang T, et al. High IGF-IR activity in triple-negative breast cancer cell the response of BRCA1 deficient breast cancer cells to PARP1 inhi- lines and tumorgrafts correlates with sensitivity to anti-IGF-IR therapy. bition. Cancer Lett 2012;319:232–41. Clin Cancer Res 2011;17:2314–27. 54. Ibrahim YH, García-García C, Serra V, He L, Torres-Lockhart K, Prat A, 58. Sharpe R, Pearson A, Herrera-Abreu MT, Johnson D, Mackay A, Welti et al. PI3K inhibition impairs BRCA1/2 expression and sensitizes BRCA JC, et al. FGFR signaling promotes the growth of triple-negative and proficient triple negative breast cancer to PARP inhibition. Cancer basal-like breast cancer cell lines both in vitro and in vivo. Clin Cancer Discov 2012;2:1036-47. Res 2011;17:5275–86.

www.aacrjournals.org Clin Cancer Res; 19(14) July 15, 2013 OF7

Molecular Pathways: PI3K Pathway Targets in Triple-Negative Breast Cancers

Vallerie Gordon and Shantanu Banerji

Clin Cancer Res Published OnlineFirst June 7, 2013.

Updated version Access the most recent version of this article at: doi:10.1158/1078-0432.CCR-12-0274

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