MAD-CT-2 identified as a novel melanoma cancer-testis antigen using phage immunoblot analysis

Inducible expression of cancer-testis antigens in human prostate cancer

Immune tolerance to self-antigens can limit robust anti-tumor immune responses in the use of tumor vaccines. Expression of novel tumor associated antigens can improve immune recognition and lysis of tumor cells. The cancer-testis antigen (CTA) family of proteins has been hypothesized to be an ideal class of antigens due to tumor-restricted expression, a subset of which have been found to induce antibody responses in patients with prostate disease. We demonstrate that CTA expression is highly inducible in five different Prostate Cancer (PC) cell lines using a hypomethylating agent 5-Aza-2′-deoxycytidine (5AZA) and/or a histone deacetylase inhibitor LBH589. These CTAs include NY-ESO1, multiple members of the MAGE and SSX families and NY-SAR35. A subset of CTAs is synergistically induced by the combination of 5AZA and LBH589. We developed an ex vivo organ culture using human PC biopsies for ex vivo drug treatments to evaluate these agents in clinical samples. These assays found significant induction of SSX2 in 9/9 distinct patient samples and NY-SAR35 in 7/9 samples. Further, we identify expression of SSX2 in circulating tumor cells (CTC) from patients with advanced PC. These results indicate that epigenetic modifying agents can induce expression of a broad range of neoantigens in human PC and may serve as a useful adjunctive therapy with novel tumor vaccines and checkpoint inhibitors.

New York esophageal squamous cell carcinoma-1 and cancer immunotherapy

New York esophageal squamous cell carcinoma 1 (NY-ESO-1) is a known cancer testis gene with exceptional immunogenicity and prevalent expression in many cancer types. These characteristics have made it an appropriate vaccine candidate with the potential application against various malignancies. This article reviews recent knowledge about the NY-ESO-1 biology, function, immunogenicity and expression in cancers as well as and the results of clinical trials with this antigen.

Lymphocyte cytosolic protein 1 is a chronic lymphocytic leukemia membrane-associated antigen critical to niche homing

Membrane antigens are critical to the pathogenesis of chronic lymphocytic leukemia (CLL) as they facilitate microenvironment homing, proliferation, and survival. Targeting the CLL membrane and associated signaling patterns is a current focus of therapeutic development. Many tumor membrane targets are simultaneously targeted by humoral immunity, thus forming recognizable immunoglobulin responses. We sought to use this immune response to identify novel membrane-associated targets for CLL. Using a novel strategy, we interrogated CLL membrane-specific autologous immunoglobulin G reactivity. Our analysis unveiled lymphocyte cytosolic protein 1 (LCP1), a lymphocyte-specific target that is highly expressed in CLL. LCP1 plays a critical role in B-cell biology by crosslinking F-actin filaments, thereby solidifying cytoskeletal structures and providing a scaffold for critical signaling pathways. Small interfering RNA knockdown of LCP1 blocked migration toward CXCL12 in transwell assays and to bone marrow in an in vivo xenotransplant model, confirming a role for LCP1 in leukemia migration. Furthermore, we demonstrate that the Bruton's tyrosine kinase inhibitor ibrutinib or the PI3K inhibitor idelalisib block B-cell receptor induced activation of LCP1. Our data demonstrate a novel strategy to identify cancer membrane target antigens using humoral anti-tumor immunity. In addition, we identify LCP1 as a membrane-associated target in CLL with confirmed pathogenic significance. This clinical trial was registered at clinicaltrials.gov; study ID number: OSU-0025 OSU-0156.

Lenalidomide modulates IL-8 and anti-prostate antibody levels in men with biochemically recurrent prostate cancer

BACKGROUND

We retrospectively explored changes in immunological parameters in men with biochemically recurrent prostate cancer treated with either 5 or 25 mg of lenalidomide in a randomized phase 2 trial, and determined whether those changes correlated with disease progression.

METHODS

Cytokine levels were compared for each patient at baseline and after 6 months of treatment with lenalidomide. Regression models for correlated data were used to assess associations of cytokine levels with lenalidomide treatment effect. Estimates were obtained using generalized estimating equations. Changes in circulating anti-prostate antibodies were evaluated using a high-throughput immunoblot technique.

RESULTS

Treatment with lenalidomide was associated with global changes in immunoreactivity to a number of prostate-associated antigens, as well as with changes in circulating levels of the T(H) 2 cytokines IL-4, IL-5, IL-10, and IL-13. Disease progression in treated patients was associated with an increase in circulating IL-8 levels, while IL-8 levels decreased significantly in non-progressors.

CONCLUSIONS

Lenalidomide demonstrates immunomodulatory properties in patients with biochemically recurrent prostate cancer. The induction of novel anti-prostate antibodies is a potential mechanism for lenalidomide response. Changes in serum IL-8 levels may serve as a potential biomarker in treated patients. These hypotheses require formal testing in future prospective trials.

Unmasking the immune recognition of prostate cancer with CTLA4 blockade

Although cancer cells can be immunogenic, tumour progression is associated with the evasion of immunosurveillance, the promotion of tumour tolerance and even the production of pro-tumorigenic factors by immune cells. Cytotoxic T lymphocyte-associated antigen 4 (CTLA4) represents a crucial immune checkpoint, the blockade of which can potentiate anti-tumour immunity. CTLA4-blocking antibodies are now an established therapeutic approach for malignant melanoma, and clinical trials with CTLA4-specific antibodies in prostate cancer have also shown clinical activity. This treatment may provide insights into the targets that the immune system recognizes to drive tumour regression, and could potentially improve both outcome and toxicity for patients with prostate cancer.

Antibody responses to prostate-associated antigens in patients with prostatitis and prostate cancer

BACKGROUND

An important focus of tumor immunotherapy has been the identification of appropriate antigenic targets. Serum-based screening approaches have led to the discovery of hundreds of tumor-associated antigens recognized by IgG. Our efforts to identify immunologically recognized proteins in prostate cancer have yielded a multitude of antigens; however, prioritizing these antigens as targets for evaluation in immunotherapies has been challenging. In this report, we set out to determine whether the evaluation of multiple antigenic targets would allow the identification of a subset of antigens that are common immunologic targets in patients with prostate cancer.

METHODS

Using a phage immunoblot approach, we evaluated IgG responses in patients with prostate cancer (n = 126), patients with chronic prostatitis (n = 45), and men without prostate disease (n = 53).

RESULTS

We found that patients with prostate cancer or prostatitis have IgG specific for multiple common antigens. A subset of 23 proteins was identified to which IgG were detected in 38% of patients with prostate cancer and 33% patients with prostatitis versus 6% of controls (P < 0.001 and P = 0.003, respectively). Responses to multiple members were not higher in patients with advanced disease, suggesting antibody immune responses occur early in the natural history of cancer progression.

CONCLUSIONS

These findings suggest an association between inflammatory conditions of the prostate and prostate cancer, and suggest that IgG responses to a panel of commonly recognized prostate antigens could be potentially used in the identification of patients at risk for prostate cancer or as a tool to identify immune responses elicited to prostate tissue.

IgG responses to tissue-associated antigens as biomarkers of immunological treatment efficacy

We previously demonstrated that IgG responses to a panel of 126 prostate tissue-associated antigens are common in patients with prostate cancer. In the current report we questioned whether changes in IgG responses to this panel might be used as a measure of immune response, and potentially antigen spread, following prostate cancer-directed immune-active therapies. Sera were obtained from prostate cancer patients prior to and three months following treatment with androgen deprivation therapy (n = 34), a poxviral vaccine (n = 31), and a DNA vaccine (n = 21). Changes in IgG responses to individual antigens were identified by phage immunoblot. Patterns of IgG recognition following three months of treatment were evaluated using a machine-learned Bayesian Belief Network (ML-BBN). We found that different antigens were recognized following androgen deprivation compared with vaccine therapies. While the number of clinical responders was low in the vaccine-treated populations, we demonstrate that ML-BBN can be used to develop potentially predictive models.

The prioritization of cancer antigens: a national cancer institute pilot project for the acceleration of translational research

The purpose of the National Cancer Institute pilot project to prioritize cancer antigens was to develop a well-vetted, priority-ranked list of cancer vaccine target antigens based on predefined and preweighted objective criteria. An additional aim was for the National Cancer Institute to test a new approach for prioritizing translational research opportunities based on an analytic hierarchy process for dealing with complex decisions. Antigen prioritization involved developing a list of "ideal" cancer antigen criteria/characteristics, assigning relative weights to those criteria using pairwise comparisons, selecting 75 representative antigens for comparison and ranking, assembling information on the predefined criteria for the selected antigens, and ranking the antigens based on the predefined, preweighted criteria. Using the pairwise approach, the result of criteria weighting, in descending order, was as follows: (a) therapeutic function, (b) immunogenicity, (c) role of the antigen in oncogenicity, (d) specificity, (e) expression level and percent of antigen-positive cells, (f) stem cell expression, (g) number of patients with antigen-positive cancers, (h) number of antigenic epitopes, and (i) cellular location of antigen expression. None of the 75 antigens had all of the characteristics of the ideal cancer antigen. However, 46 were immunogenic in clinical trials and 20 of them had suggestive clinical efficacy in the "therapeutic function" category. These findings reflect the current status of the cancer vaccine field, highlight the possibility that additional organized efforts and funding would accelerate the development of therapeutically effective cancer vaccines, and accentuate the need for prioritization.

Treatment of chronic lymphocytic leukemia with a hypomethylating agent induces expression of NXF2, an immunogenic cancer testis antigen

PURPOSE

Critical to the success of active immunotherapy against cancer is the identification of immunologically recognized cancer-specific proteins with low tolerogenic potential. Cancer testis antigens (CTA), in particular, fulfill this requirement as a result of their aberrant expression restricted to cancer cells and lack of expression in normal tissues bypassing tolerogenic mechanisms against self. Although CTAs have been extensively studied in solid malignancies, little is known regarding their expression in chronic lymphocytic leukemia (CLL).

EXPERIMENTAL DESIGN

Using a two-pronged approach we evaluated the immunogenicity of 29 CTAs in 22 patients with CLL and correlated these results to reverse transcriptase PCR data from CLL cell lines and patient cells.

RESULTS

We identified IgG-specific antibodies for one antigen, NXF2, and confirmed this response by ELISA and Western blot. We found that treatment of CLL with 5-aza-2'-deoxycytidine can induce expression of NXF2 that lasted for several weeks after treatment. Treatment also increased levels of MHC and costimulatory molecules (CD80, CD86, and CD40) necessary for antigen presentation. In addition, we identified other promising antigens that may have potential immunotherapeutic application.

CONCLUSIONS

Our findings suggest that NXF2 could be further pursued as an immunotherapeutic target in CLL, and that treatment with demethylating agents could be exploited to specifically modulate CTA expression and effective antigen presentation in malignant B cells.

Potentiating endogenous antitumor immunity to prostate cancer through combination immunotherapy with CTLA4 blockade and GM-CSF

CTL-associated antigen 4 (CTLA4) is a costimulatory molecule expressed on activated T cells that delivers an inhibitory signal to these T cells. CTLA4 blockade with antibody treatment has been shown to augment antitumor immunity in animal models and is being developed as a treatment for cancer patients. As has been seen in preclinical models, combining CTLA4 blockade and granulocyte macrophage colony-stimulating factor (GM-CSF)-based immunotherapies can enhance the antitumor efficacy of this approach. We therefore examined whether CTLA4 blockade could be combined with GM-CSF administration. We treated 24 patients with metastatic, castration-resistant prostate cancer in a phase I trial where sequential cohorts were treated with increasing doses of ipilimumab, a fully human anti-CTLA4 antibody. Study subjects also received s.c. injections of GM-CSF at a fixed dose. Of the six patients treated at the highest dose level, three had confirmed PSA declines of >50%, including one patient that had a partial response in visceral metastases. Expansion of activated, circulating CD25(+) CD69(+) CD8(+) T cells occurred more frequently at higher doses of treatment and was greater in magnitude than was seen in patients who received the same doses of either ipilimumab or GM-CSF alone. By screening sera with protein arrays, we showed that our treatment can induce antibody responses to NY-ESO-1. These results show that this combination immunotherapy can induce the expansion not only of activated effector CD8 T cells in vivo but also of T cells that are specific for known tumor-associated antigens from the endogenous immune repertoire.