A Strong Case for Personalized, Targeted Cancer Prevention

Cancer Prevention Perspective Research Perspective on Lee, et al., p. 185

Marcia I. Dawson

Abstract The study reported by Lee and colleagues in this issue of the journal (beginning on page 185) incorporated global genetic variation within a new assessment of the outcome of a previously reported phase-III trial of low-dose 13-cis-retinoic acid (13-cRA) for preventing second primary tumors (SPT) or the recurrence of head-and-neck cancer. This analysis identified genotypes of common single-nucleotide polymorphisms (SNP) and cumulative effect and potential gene–gene interactions that were highly associated with increased placebo-arm risk (prognostic) and/or with reduced treatment-arm risk and longer event-free survival (predictive). For example, the wild-type rs3118570 SNP of the retinoid X receptor alpha gene (carried by 71% of the 13-cRA trial population) marked a 3.33-fold increased SPT/recurrence risk in the placebo arm and a 38% reduced risk in the treatment arm. Adding two other informative genotypes strengthened the treatment-arm risk reduction to 76%, although the genotype trio reflected only 13% of the trial population. This report extends the concept of personalized therapy to cancer prevention. Cancer Prev Res; 4(2); 173–6. 2011 AACR.

The retinoid 13-cis-retinoic acid (13-cRA, or isotretinoin) function as transcription factors. In the presence of light or a once was among the most promising agents for cancer mercaptansuchasreducedglutathione,RAs undergodouble- chemoprevention in the modern day. Outcomes of phase- bond isomerizations to produce mixtures containing about III cancer prevention trials of 13-cRA in the lung and head 80% ATRA and 8% to 10% 9-cRA (5–7). Therefore, dosing and neck, however, were disappointing (1–3). Now in this with 13-cRA was anticipated to minimize the adverse effects issue of the journal (4), Lee and colleagues report an caused by administering high levels of the transcriptionally additional assessment of one of these phase-III trials, which active RA isomers (8). However, even at the low dose levels evaluated 13-cRA for head-and-neck cancer prevention, used in cancer prevention trials, subjects taking oral 13-cRA that brings new hope for successful cancer prevention with haveexperiencedsignificantdose-relatedtoxic effects (9–11). retinoids in certain at-risk populations and suggests that The major cause of head-and-neck squamous cell outcome analyses incorporating genotypic data can detect carcinoma (SCC) is the use of tobacco and the subsequent positive aspects of otherwise negative cancer prevention exposure to its carcinogens and irritants. Indeed, 85% of trials. This new study also provides a proof of principle of head-and-neck cancers have been linked to tobacco use the potential of pharmacogenetics to personalize cancer (smoking and chewing; ref. 12). Although human papil- prevention. lomavirus (HPV) is a rapidly increasing cause of head-and- 13-cRAiscurrentlyusedforthesystemictreatmentofsevere neck cancer (predominantly through effects in the orophar- cystic acne and other cutaneous conditions such as severe ynx; ref. 13), this cause did not play a major role in the acne rosea, harlequin ichthyosis, and xeroderma pigmento- population of the phase-III 13-cRA trial examined by Lee sum keratoses. This RA isomer is considered to be transcrip- and colleagues (4). In 2010, the U.S. yearly incidence of tionally inactive and functions instead as a prodrug that is head-and-neck SCC, which includes the upper aerodiges- transformed in vivo to all-trans-retinoic acid (ATRA, or treti- tive tract sites of the oral cavity, pharynx, and larynx, was noin) and its 9-cis isomer (9-cRA, or alitretinoin). Both ATRA estimated to be more than 49,000 cases (3% of all new and 9-cRA have roles in regulating cell proliferation and cancers) by the American Cancer Society; the annual num- inducing cell differentiation through their interaction with ber of deaths from this disease was estimated to be approxi- nuclear retinoid X receptors (RXR) and RA receptors that mately 11,500 (14). With an annual incidence estimated at more than 0.5 million cases, head-and-neck cancer is the fifth most common cancer worldwide. Stage I–II disease is Author's Affiliation: Cancer Center, Sanford-Burnham Medical Research usually curatively treated by surgical resection and/or radia- Institute, La Jolla, California tion; long-term survival, however, has continued to be Corresponding Author: Marcia I. Dawson, Cancer Center, Sanford-Burn- problematic because of frequent recurrence and the devel- ham Medical Research Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037. Phone: 858-646-3165; Fax: 858-646-3197. opment of second primary tumors (SPT). Head-and-neck E-mail: [email protected] cancer development is a multistep process that involves the doi: 10.1158/1940-6207.CAPR-10-0386 accumulation of genetic and epigenetic alterations in 2011 American Association for Cancer Research. chromosomes including 3p, 9p, 13q, and 17p and gene

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mutations leading to constitutive activation of oncogenes Genotyping in these patients involved 9,645 candidate and loss of function of tumor suppressor genes, many of SNPs derived from 998 cancer-related genes having roles which have been shown to be associated with SPT appear- in 12 cellular signaling pathways. Seven chromosomal SNPs ance or cancer recurrence (15). Khuri and colleagues were significantly associated with the risk of SPT/recurrence (1, 16) reported that about 15% to 25% of early-stage after adjusting for multiple comparison, and genes asso- head-and-neck SCC patients developed SPTs and 10% had ciated with these SNPs have roles in cellular processes such local recurrences within 5 years of surgery and/or radiation. as proliferation, DNA repair, stem-cell differentiation, car- The original analysis of the phase-III trial of 13-cRA to cinogen metabolism, growth-factor signaling, and apopto- prevent SPTs and recurrence of head-and-neck cancer sis. Six mitochondrial DNA SNPs also were associated with (recruitment from 1991–1999) did not support continued an increased risk of SPT/recurrence after multiple compar- investigation of 13-cRA as a cancer preventive agent (1). The ison adjustment. The authors concluded that the most trial randomly assigned 1,190 stage-I and stage-II head-and- significant mitochondrial SNP was that located in the neck cancer patients to low-dose 13-cRA or placebo. These NADH dehydrogenase subunit 4 (ND4) gene, which pre- patients had previously undergone surgical resection and/or viously had been found to be associated with head-and- radiation therapy and were disease-free at 16 weeks or more neck cancer (19). The protein encoded by ND4 is a subunit 4 after treatment. SPTs were defined as tumors that appeared of the NADH dehydrogenase, which resides in the mito- at least 3 years after the primary tumor and had a different chondrial respiratory chain that generates ATP complex I, histology than or were 2 cm or more away from it; recur- and has a role in carcinogen metabolism. Two other mito- rence was defined as new cancer with a similar histology to chondrial SNPs associated with altered risk were SNPs of the the primary tumor and occurring within 2 cm or within 3 mitochondrial cytochrome B gene (mtCYB), which encodes years of primary tumor diagnosis. Combining SPTs and the P450 enzyme mtCYB, another component of the recurrence in this trial reflects the problem of distinguishing respiratory chain and also found to be associated with between these two treatment failures in the head and neck head-and-neck cancer. A deletional mutation leading to and lung. Patients who developed symptoms of grade-2 or overexpression of mtCYB is reported to increase reactive higher toxicity (29.5% on 13-cRA and 9.2% on placebo) oxygen species (ROS; ref. 20) and to enhance bladder cancer were withdrawn from treatment until symptoms of toxicity cell proliferation (21). Tobacco carcinogens also increase resolved, and then they were allowed to resume therapy ROS leading to DNA damage, thereby suggesting an additive until toxicity recurred, when their drug dosage was reduced. relationship between tobacco use and mtCYB activity. No statistically significant reduction in the rates of SPT Wu and colleagues constructed prediction models, as (HR ¼ 1.06; 95% CI, 0.83–1.35) or recurrence (HR ¼ illustrated by receiver operating characteristic curves in 0.79; 95% CI, 0.55–1.14) and no increased survival time their Figure 2 (18), by adding these genetic variables to (HR ¼ 1.03; 95% CI, 0.81–1.71) occurred in the 13-cRA the clinical (tumor stage, site, and treatment) and smoking treatment arm compared with the placebo arm. (pack-years) variables. They showed that the area-under- Even before providing a platform for genotyping studies, the curve increased dramatically from 0.64 (clinical and the most recent of which was conducted by Lee and collea- smoking variables) to 0.84 (clinical, smoking, and genetic gues (4), this phase-III 13-cRA trial provided a valuable variables), indicating a significant improvement in predic- platform for assessing associations of outcome (in either or tion efficiency with the addition of genetic variables. The in the combined arms) with disease stage and smoking authors pointed out that a blood draw is a far less-invasive status (1). Coming from a large-scale, prospective phase-III and less-expensive method of obtaining samples for geno- trial in carefully characterized and followed (long-term) typing than is biopsy via bronchoscopy. patients, these associations were robust. Patients with This global genotyping study of the phase-III 13-cRA trial stage-II disease were found to have higher rates of SPT analyzed the prognostic value of SNPs in a combined group and recurrence, and lower overall survival than did those of patients from the placebo and treatment arms. Lee and with stage-I disease. Multivariable regression analyses indi- colleagues (4) have gone a step (13-cRA or placebo) further cated that current and former smokers had increased rates of by stratifying the same genotyping data by treatment in the SPT appearance (2.5-fold) and death (1.6-fold) compared same patient population used by Wu and colleagues (18). with nonsmokers. These findings resolved previously mixed This new study first identified prognostic loci for increased data on the consequences of smoking to the risk of head- SPT/recurrence risk in the placebo group, focusing on the and-neck SPTs and cancer recurrence. previously genotyped chromosomal SNPs (not the much The influence of a patient’s genetic background on the risk lower number of mitochondrial SNPs), and then examined and prognosis of cancer is increasingly recognized (17). A whether these loci also identified individuals who received previous analysis of this phase-III 13-cRA trial involved the benefit from 13-cRA treatment. Furthermore, by focusing on first comprehensive global genotyping approach to analyz- wild-type genotypes (or common genotypes present in the ing clinical trial results in this setting (18). That analysis majority of the population) associated with an increased assessed associations between certain single-nucleotide placebo-arm SPT/recurrence risk and a reduced 13-cRA-arm polymorphisms (SNP) and an increased risk of SPT/recur- risk, this study aimed to identify genotypes that could mark a rence among 150 patients with and 300 matched controls substantial proportion of the patients who might benefit without SPT/recurrence from the original trial population. from 13-cRA prevention. The wild-type genotypes of 45

174 Cancer Prev Res; 4(2) February 2011 Cancer Prevention Research

SNPs were associated with an increased risk of SPT/recur- predictive markers. No overlaps in the top hits occurred rence in the placebo group. Of these 45 loci, 17 were between the unstratified and stratified analyses of the associated with a decreased risk of SPT/recurrence in the same panel of chromosomal SNPs in the same patients, 13-cRA group (compared with placebo), and 13 were sta- which is not surprising. Further research remains to be tistically significantly (P < 0.05). Placebo patients with wild- done to discern how each of the risk-reducing genotypes type genotypes for SNPs in the genes for RXR-alpha (RXRA), and their related proteins exert protective effects in com- Janus kinase 2 (JAK2), metalloproteinase 3 (MMP3), bination with 13-cRA. RAD54-like (RAD54L), and cell division cycle 25 homolo- It is hoped that such predictive analyses can be extended gue C (CDC25C) had a 1.85- to 3.57-fold higher risk of SPT/ to other large cohorts, including cohorts of people at risk of recurrence. Of note, placebo patients with the wild-type primary head-and-neck cancer, head-and-neck cancer genotype RXRA rs3118570 (present in 71% of the trial patients, and long-term randomized trials of retinoids that population) exhibited a 3.33-fold increased risk of SPT/ had original statistical analyses of outcomes leading to recurrence, and 13-cRA–treated patients with this genotype conclusions that their treatments had failed to prevent had a 38% reduction in SPT/recurrence risk and a 1.5-year SPT development or recurrence (17). Such trials include longer event-free survival than the placebo patients with the the phase-III U.S. National Cancer Institute Lung Inter- same genotype. Furthermore, patients in the treatment arm group Trial of 13-cRA to prevent recurrence and/or SPTs in with the wild-type JAK2 and CDC25C genotypes plus the the setting of non–small-cell lung cancer (2, 3) and a phase- RXRA wild-type genotype (representing 13% of the trial III trial of N-(4-hydroxyphenyl) all-trans-retinamide (fen- population) had an increased benefit from 13-cRA of a retinide) to prevent recurrence and/or SPTs in the setting of 76% reduced risk for SPT/recurrence and a more than 5 years breast cancer (25). event-free survival advantage (versus placebo-arm patients In conclusion, the important genotyping work reported with the same 3 genotypes). Subgroup analyses of SPT or by Lee and colleagues in this issue of the journal (4) in the recurrence only in the head and neck or lung revealed the setting of recurrence and SPTs in head-and-neck cancer same pattern of prognostic and predictiveeffects for 2 (RXRA patients indicates the potential of genotyping for helping to and JAK2) of the 3 SNPs. Although RXRA, JAK2, and personalize cancer prevention. Although perhaps less CDC25C were most significant, several genetic loci within advanced than this global approach in a phase-III clinical TSC1 (which regulates PI3K/AKT/mTOR signaling, a trial, genotyping work in other sites, including the color- critical pathway in head-and-neck carcinogenesis) were ectum (aspirin, celecoxib, statins), prostate (selenium), among the top hits (e.g., Table 2 of ref. 4), which supports and bladder (BCG), is beginning to make headway toward future, more-depthful genotyping analysis of this pathway personalized cancer prevention as well (26–29). Similar that may further improve the prediction models in this personalized genotyping approaches are being applied in setting. research in tobacco dependence (30) and cancer therapy The analysis of Lee and colleagues (4) highlights the (31). Although Lee and colleagues did internal validation importance of stratifying global genotyping analyses by of their results using a bootstrap resampling analysis, it will treatment and the limited ability of unstratified (by be important to test their findings in an external validation treatment) analyses to detect markers with predictive cohort. It also will be important to extend global genotyp- effects in treated individuals and prognostic effects in ing analyses to cohorts of patients with HPV-associated untreated individuals that are opposite to each other. head-and-neck cancer since HPV-related cases are increas- For example, the RXRA SNPwasnotobservedtobe ing dramatically, have distinct risk factors and clinical significantly associated with SPT/recurrence risk in the features (13, 32), and likely will not have the same prog- unstratified analysis of Wu and colleagues (18). Its effect nostic and predictive profiles that classic smoking-related was essentially "washed-out" by the difference in the cases have. The combined results of all such analyses may placebo and 13-cRA arms. This wash-out likely also culminate in a strong case for personalized, targeted cancer occurred in 3 other unstratified/combined-arm studies prevention. focusing on SPT/recurrence prognostic factors by the same group of investigators in the phase-III 13-cRA trial Disclosure of Potential Conflicts of Interest (22–24). In the past, investigators have tended to com- bine arms for genotyping studies of negative/neutral No potential conflicts of interest were disclosed. trials. These previous unstratified, combined-arm analyses produced significant prognostic factors. The present Received October 18, 2010; revised December 12, 2010; accepted stratified-by-treatment analysis suggests prognostic and December 21, 2010; published online February 3, 2011.

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Marcia I. Dawson

Cancer Prev Res 2011;4:173-176.

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