Immunotherapy of MDS: You Can Run, but You Can’T Hide

Author Manuscript Published OnlineFirst on December 28, 2017; DOI: 10.1158/1078-0432.CCR-17-2960 Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited.

Immunotherapy of MDS: you can run, but you can’t hide

Ephraim Joseph Fuchs, MD, MBA Division of Hematologic Malignancies, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins Baltimore, MD, USA e-mail: [email protected]

Running title: Hypomethylating agents to enhance cancer vaccines for MDS

Conflicts of Interest: The author has no conflicts of interest

Downloaded from clincancerres.aacrjournals.org on October 3, 2021. © 2017 American Association for Cancer Research. Author Manuscript Published OnlineFirst on December 28, 2017; DOI: 10.1158/1078-0432.CCR-17-2960 Author manuscripts have been peer reviewed and accepted for publication but have not yet been edited.

Summary: The hypomethylating agent decitabine induces expression of the cancer testis antigen NY-

ESO-1 in the myeloid cells of patients with myelodysplastic syndrome (MDS). MDS patients treated with decitabine and an NY-ESO-1 vaccine developed NY-ESO-1-specific T cell responses directed against their abnormal myeloid cells, raising hopes for combinatorial immunotherapy of this disease.

In this issue of Clinical Cancer Research, Griffiths and colleagues conduct a phase I clinical trial in patients with myelodysplastic syndrome (MDS) of a combinatorial immunotherapy (Figure 1) comprising the hypomethylating agent decitabine plus a vaccine against the “cancer testis” antigen NY-ESO-1 (1).

This strategy addresses a critical unmet need in cancer immunotherapy: the treatment of cancers with few available immunologic targets.

The success of the immunologic checkpoint inhibitors (CIs) and of chimeric antigen receptor-modified T cells, or CAR T cells, has raised the level of enthusiasm for cancer immunotherapy to a fever pitch.

Studies on the mechanism of the anti-tumor effect of the anti-CTLA-4 antibody ipilimumab or the anti-

PD-1 antibodies nivolumab or pembrolizumab have shown that these CIs stimulate endogenous (i.e. patient-derived) T cells specific for tumor “neoantigens”(2), tumor-specific antigens that result from somatic mutation. The reactivity of CAR T cells against tumor cells is achieved by inserting into T cells a receptor whose extracellular domain consists of the antigen-binding portion of an antibody reactive to a molecule on the tumor cell surface, while the intracellular portion triggers the cytolytic machinery of the

T cell. Thus, CAR T cells combine the exquisite specificity of antibodies for protein antigens with the lethality of cytotoxic T cells.

Still, there are major obstacles to the broad application of immunotherapy to the treatment of several common tumor types. For example, the efficacy of CIs is limited primarily to tumors with large numbers of clonal mutations(3). Even in tumors with a high mutational burden, such as melanoma or lung

cancer, response rates to checkpoint inhibitors rarely exceed 50%, and clonal escape from immune surveillance or active resistance mechanisms are common(4). Tumors with low numbers of somatic mutations, such as pediatric cancers or cancers of the breast, prostate, ovary, or pancreas generally respond poorly to CIs. The major limitation to CAR T cells is that the target of the chimeric receptor must be expressed on the cell surface, yet there are no cell surface molecules that distinguish a cancer cell from its normal tissue counterpart. Thus, CAR T cells are tissue-specific rather than tumor-specific and can only be used to treat cancers deriving from tissues, such as B lymphocytes, that are not essential to the survival of the patient.

So, what can be done to stimulate an effective anti-tumor immune response against cancers with no unique targets on the cell surface and a low mutational burden? This is the challenge that Griffiths et al. confronted in developing an approach to the immunotherapy of myelodyspastic syndrome, or MDS.

MDS is a clonal hematopoietic disorder characterized by ineffective hematopoiesis and an inexorable progression to acute myeloid leukemia. Since the molecules on the surface of MDS cells are all expected to be expressed on normal white blood cells, it would be difficult if not impossible to target MDS with

CAR T cells without unacceptable toxicities. Further, MDS is characterized by a low mutational burden and checkpoint inhibitors have only modest activity against this disease(5).

The only approved therapies of the myelodysplastic syndromes are the hypomethylating agents (HMAs), azacitidine and decitabine. While their mechanism of action has not been fully defined, several lines of evidence suggest that demethylation of promoter regions enables the re-expression of potentially immunogenic proteins leading to a therapeutic anti-tumor immune response. One such protein with inducible on myeloid cells is the cancer/testis antigen, NY-ESO-1. Cancer/testis antigens are a heterogeneous group of proteins that are normally expressed in germ cells and in diverse types of cancers, but not in differentiated tissues of the adult. However, NY-ESO-1 is constitutively expressed in

up to one third of patients with melanoma, lung, esophageal, liver, gastric, prostate, ovarian, or bladder cancers(6), and antibodies against NY-ESO-1 can be found in the serum of such patients. In patients with MDS or acute myeloid leukemia, the promoter region of the NY-ESO-1 gene is heavily methylated, and so the protein is not usually made in the malignant cells.

In a previous study, the authors showed that the expression of cancer testis antigens NY-ESO-1 and

MAGEA3/A6 is induced on AML blasts in patients treated with decitabine(7). This finding raised the possibility that decitabine could be used to increase NY-ESO-1 expression in blasts while a vaccine against NY-ESO-1 could be administered to generate a cytotoxic T cell response from autologous T cells specific for this antigen. In the current study, Griffiths et al. conducted a phase I trial in which nine patients with MDS received an HLA-unrestricted NY-ESO-1 vaccine (CDX-1401 + poly-ICLC) every four weeks with standard dose decitabine. NY-ESO-1 expression was induced in all seven patients who reached the end of the study, and NY-ESO-1-specific CD4+ and CD8+ T cell responses were seen in 6/7 and 4/7 vaccinated patients, respectively. Myeloid cells, isolated from a patient at different time points during decitabine therapy, expressed NY-ESO-1 and activated a cytotoxicity from autologous, NY-ESO-1- specific T cells. The intensity of the T and B cell response to NY-ESO-1 vaccination was somewhat heterogeneous, but appeared to correlate with the pre-vaccination frequency of dendritic cells (DCs) that express the cell surface marker CD141. Perhaps this correlation is not surprising as these DCs express high levels of DEC-205, which is targeted by the vaccine, and TLR3, which is targeted by the vaccine adjuvant. Finally, a clinical response to decitabine plus NY-ESO-1 vaccination was associated with an increase in the frequency of CD141HI DCs in the bone marrow.

Although the results of this combinatorial strategy are encouraging, some observations need further characterization and explanation. First, there was not a consistent correlation between immunologic and clinical responses. The patient with the best immunologic response to treatment achieved a

durable complete remission, but the next best immunologic responder (patient 2) only had stable disease following treatment. Second, one patient (#6) expressed NY-ESO-1 in myeloid cells prior to decitabine treatment, but this was not associated with an endogenous immune response. Finally, one patient (#7) experienced a durable complete remission despite a relatively weak induction of CD4+ T cells and no induction of CD8+ T cells. One explanation for a dissociation between NY-ESO-1 expression and response to vaccination is that some patients may be immunologically tolerant of NY-ESO-1.

Although NY-ESO-1 is generally not expressed in adult tissues, it has been found to be expressed in the medullary thymic epithelium(8), where it can induce tolerance in developing T cells. Indeed, cancer/testis antigen-specific T cells isolated from cancer patients often have suboptimal affinity and do not mediate significant killing(9), suggesting that high affinity clones have been physically or functionally deleted from the repertoire. While this finding may bode poorly for strategies of cancer vaccination, decitabine-induced expression of cancer/testis antigens could be combined effectively with adoptive immunotherapy with high affinity T cells specific for these antigens.

In summary, Griffiths and colleagues have provided an elegant tool for sensitizing cancer cells to tumor- specific T cells by using a demethylating agent to express otherwise cryptic antigens. Further studies will be required to determine the generalizability of this approach.

1. Griffiths EA, Srivastava P, Matsuzaki J, Brumberger Z, Wang ES, Kocent J, et al. NY-ESO-1 Vaccination in Combination with Decitabine Induces Antigen-Specific T-Lymphocyte Responses in Patients with Myelodysplastic Syndrome. Clin Cancer Res. 2017. 2. Gubin MM, Zhang X, Schuster H, Caron E, Ward JP, Noguchi T. Checkpoint blockade cancer immunotherapy targets tumour-specific mutant antigens. Nature. 2014;515. 3. Riaz N, Havel JJ, Makarov V, Desrichard A, Urba WJ, Sims JS, et al. Tumor and Microenvironment Evolution during Immunotherapy with Nivolumab. Cell. 2017. 4. McGranahan N, Rosenthal R, Hiley CT, Rowan AJ, Watkins TBK, Wilson GA, et al. Allele-Specific HLA Loss and Immune Escape in Lung Cancer Evolution. Cell. 2017;171:1259-71.e11. 5. Garcia-Manero G, Tallman MS, Martinelli G, Ribrag V, Yang H, Balakumaran A, et al. Pembrolizumab, a PD-1 Inhibitor, in Patients with Myelodysplastic Syndrome (MDS) after Failure of Hypomethylating Agent Treatment. Blood. 2016;128:345-. 6. Gnjatic S, Nishikawa H, Jungbluth AA, Gure AO, Ritter G, Jager E, et al. NY-ESO-1: review of an immunogenic tumor antigen. Advances in cancer research. 2006;95:1-30. 7. Srivastava P, Paluch BE, Matsuzaki J, James SR, Collamat-Lai G, Blagitko-Dorfs N, et al. Induction of cancer testis antigen expression in circulating acute myeloid leukemia blasts following hypomethylating agent monotherapy. Oncotarget. 2016;7:12840-56. 8. Gotter J, Brors B, Hergenhahn M, Kyewski B. Medullary epithelial cells of the human thymus express a highly diverse selection of tissue-specific genes colocalized in chromosomal clusters. J Exp Med. 2004;199:155-66. 9. Obenaus M, Leitao C, Leisegang M, Chen X, Gavvovidis I, van der Bruggen P, et al. Identification of human T-cell receptors with optimal affinity to cancer antigens using antigen-negative humanized mice. Nat Biotech. 2015;33:402-7.

Figure 1. Combinatorial strategy to sensitize neoplastic myeloid cells of MDS patients to killing by T cells specific for the cancer testis antigen, NY-ESO-1. Decitabine demethylates the promoter region of the NY-ESO-1 gene, leading to upregulation of transcription and translation of the NY-ESO-1 protein in neoplastic myeloid cells(bottom). Meanwhile, the CDX-1401 vaccine, a fusion protein containing the full length NY-ESO-1 protein linked to an antibody against the dendritic cell surface molecule DEC-205, is taken into CD141HI dendritic cells (DCs) as the DCs are being activated by the adjuvant, poly-ICLC, binding to the intracellular Toll-like receptor, TLR3. Once taken into the cell, the fusion protein is processed by the proteasome and peptides of NY-ESO-1 are presented in the context of major histocompatibility molecules to NY-ESO-1-specific CD4+ (not shown) and CD8+ T cells. Activated CD8+ cytotoxic T lymphocytes (CTLs) can then secrete interferon gamma and kill neoplastic myeloid cells presenting the cognate NY-ESO-1 peptide.

Figure 1:

CD141+ DC poly-ICLC NY-ESO-1- speciﬁc CDX-1401 CD8+ T cell

DEC-205 TLR3 NY-ESO-1- speciﬁc CTL

NY-ESO-1

Gene expression repressed Gene expression

CpG island NY-ESO-1 CpG island NY-ESO-1

Myeloid cell Myeloid cell

Decitabine

Immunotherapy of MDS: you can run, but you can't hide

Ephraim J Fuchs

Clin Cancer Res Published OnlineFirst December 28, 2017.

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