CD4-positive T-helper cell responses to the PASD1 protein in patients with diffuse large B-cell lymphoma

Therapeutic vaccines for aggressive B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common aggressive B-cell lymphoma and highly heterogeneous disease. With the standard immunochemotherapy, anti-CD20 antibody rituximab (R-) plus CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy, 30-40% of DLBCLs are refractory to initial immunochemotherapy or experience relapse post-therapy with poor clinical outcomes despite salvage therapies. Mechanisms underlying chemoresistance and relapse are heterogeneous across DLBCL and within individual patients, representing hurdles for targeted therapies targeting a specific oncogenic signaling pathway. In recent years, paradigm-shifting immunotherapies have shown impressive efficacy in various cancer types regardless of underlying oncogenic mechanisms. Vaccines are being developed for DLBCL to build protective immunity against relapse after first complete remission and to promote antitumor immune responses synergizing with immune checkpoint inhibitors to treat refractory/relapsed patients. This article provides a brief review of current progress in vaccine development in DLBCL and discussion on immunologic mechanisms underlying the therapeutic effectiveness and resistance.

PAS Domain Containing Repressor 1 (PASD1) Promotes Glioma Cell Proliferation Through Inhibiting Apoptosis In Vitro

Background

PAS domain containing repressor 1 (PASD1), the cancer-testis antigen (CTA), has been reported to be aberrantly expressed in various cancer tissues and cancer cell lines; however, normal PASD1 expression can be detected in normal tissue, excluding testicular tissue. Moreover, PASD1 is reported to be abnormally expressed in various malignant tumors. However, it remains unclear whether PASD1 participates in tumorigenesis of glioma.

Material/Methods

PASD1 expression was detected by immunohistochemistry in 155 glioma tissue specimens in this study. Furthermore, the relationship of PASD1 expression with clinicopathological features in glioma cases was statistically analyzed. In addition, PASD1 was knocked down by small interference RNA (shRNA) in glioma cell line (LN229), so as to assess the potential to use it as the target for treating glioma.

Results

Our findings suggested that PASD1 expression in glioma patients was extremely upregulated compared with that in normal tissue samples and cell lines. Moreover, PASD1 expression was found to be markedly correlated with gender, The World Health Organization grade and p53 expression; in addition, high PASD1 expression indicated poor prognosis for glioma patients. Additionally, downregulation of PASD1 inhibited the proliferation ability of cells and resulted in cell arrest at the G2/M phase, which was achieved through accelerating apoptosis. Furthermore, our results indicated that PASD1 downregulation could upregulate some apoptosis-modulating proteins at the same time it downregulated some cycle-regulating proteins.

Conclusions

Taken together, our findings demonstrated that PASD1, an oncogene, can potentially serve as an independent prognostic factor for glioma patients.

Validation of immunogenic PASD1 peptides against HLA-A*24:02 colorectal cancer

Colorectal cancer is the third commonest malignancy in Asia including Malaysia. The immunogenic cancer-testis antigens, which are expressed in a variety of cancers but with limited expression in normal tissues except the testis, represent an attractive approach to improve treatment options for colorectal cancer. We aimed to validate four PASD1 peptides as the immunotherapeutic targets in colorectal cancer. First, PASD1 mRNA and protein expression were determined via real-time polymerase chain reaction (RT-PCR) and immunohistochemistry. The PASD1 peptides specific to HLA-A*24:02 were investigated using IFN-y-ELISpot assay, followed by the cytolytic and granzyme-B-ELISpot assays to analyze the cytolytic effects of CD8⁺ T cells. Gene and protein expressions of PASD1 were detected in 20% and 17.3% of colorectal cancer samples, respectively. PASD1(4) peptide was shown to be immunogenic in colorectal cancer samples. CD8⁺ T cells raised against PASD1(4) peptide were able to lyze HLA-A*24:02+ PASD1+ cells. Our results reveal that PASD1(4) peptide represents a potential target for colorectal cancer.

Cellular immune responses against cancer-germline genes in cancers

BACKGROUND

Cancer-germline genes are a class of genes that are normally expressed in testis, trophoblast and few somatic tissues but abnormally expressed in tumor tissues. Their expression signature indicates that they can induce cellular immune responses, thus being applied as targets in cancer immunotherapy.

OBJECTIVES

To obtain the data of cellular immune responses against cancer-germline genes in cancer.

METHODS

We searched PubMed/Medline with the key words cancer-germline antigen, cancer-testis antigen, CD4+ T cell, CD8+ T cell and cancer.

RESULTS

About 40 cancer-germline genes have been shown to induce T cell specific responses in cancer patients. Melanoma, lung and breast cancer are among the mostly assessed cancer types. Several epitopes have been identified which can be used in immunotherapy of cancer.

CONCLUSION

Cellular immune responses against cancer-germline genes are indicative of appropriateness of these genes as therapeutic targets.

Sp17 Protein Expression and Major Histocompatibility Class I and II Epitope Presentation in Diffuse Large B Cell Lymphoma Patients

Improved therapies are urgently needed for patients with diffuse large B cell lymphoma (DLBCL). Success using immune checkpoint inhibitors and chimeric antigen receptor T cell technology has fuelled demand for validated cancer epitopes. Immunogenic cancer testis antigens (CTAs), with their widespread expression in many tumours but highly restricted normal tissue distribution, represent attractive immunotherapeutic targets that may improve treatment options for DLBCL and other malignancies. Sperm protein 17 (Sp17), a CTA reported to be immunogenic in ovarian cancer and myeloma patients, is expressed in DLBCL. The aim of the present study was to investigate Sp17 epitope presentation via the presence of a cytotoxic T cell (CTL) and a CD4 T-helper (Th) response in DLBCL patients. A significant γ-interferon CTL response was detected in peripheral blood mononuclear cells of 13/31 DLBCL patients following short-term cell stimulation with two novel HLA-A^⁎0201 peptides and one previously reported HLA-A^⁎0101-restricted nine-mer Sp17 peptide. No significant responses were detected in the HLA-A^⁎0201-negative DLBCL patients or four healthy subjects. A novel immunogenic 20-mer CD4 Th Sp17 peptide was detected in 8/17 DLBCL patients. This is the first report of a CTL and a CD4 Th response to Sp17 in DLBCL and supports Sp17 as a potential immunotherapeutic target for DLBCL.

Peripheral blood T cell alterations in newly diagnosed diffuse large B cell lymphoma patients and their long-term dynamics upon rituximab-based chemoimmunotherapy

The importance of T cell-dependent immune responses in achieving long-term cure of chemoimmunotherapy-treated cancer patients is underscored by the recently described "vaccinal effect" exerted by therapeutic mAbs. In accordance, pre- and post-therapy peripheral blood lymphopenia represents a well-established negative prognostic factor in DLBCL. We analyzed the phenotypic and functional (IFNγ production, and Granzyme B (GrzB) cytotoxic granule marker expression) profile of peripheral blood T lymphocyte subsets ("conventional" CD4+ and CD8+, FOXP3+CD25bright Treg, and "innate-like" CD56+) in DLBCL patients at diagnosis, and assessed the long-term impact of R-CHOP chemoimmunotherapy, in a prospective study. At diagnosis, DLBCL patients showed lower lymphocyte counts, due to selective decrement of CD4+ T (including Treg) and B lymphocytes. While all T cell subsets transiently decreased during therapy, CD4+ T cell and Treg remained significantly lower than controls, up to 1 year after R-CHOP. Phenotypically skewed profile of CD4+ and CD8+ T cell subsets associated with higher frequencies of IFNγ+ and GrzB+ cells at diagnosis, that transiently decreased during therapy, and re-attained persistently elevated levels, till up to 1 year after therapy. Differently, the pre-therapy elevated levels of circulating monocytes, and of plasma IL-6 and IL-10 rapidly normalized upon R-CHOP. In sum, we describe a quantitatively and functionally altered status of the peripheral blood T cell compartment in DLBCL patients at diagnosis, that persists long-term after tumor eradication, and it is only transiently perturbed by R-CHOP chemoimmunotherapy. Moreover, data suggest the association of selected T cell functional features with DLBCL phenotype, and with therapy outcome.

Low Level of Blood CD4+ T Cells Is an Independent Predictor of Inferior Progression-free Survival in Diffuse Large B-cell Lymphoma

BACKGROUND

Tumor-infiltrating immune cells influence diffuse large B-cell lymphoma (DLBCL) outcomes. Relatively little, however, is known about the significance of peripheral blood immune cell numbers on DLBCL behavior.

PATIENTS AND METHODS

In the present study, 43 patients with newly diagnosed DLBCL had pretreatment multiparameter peripheral blood flow cytometry performed to assess the immune cell numbers. These cell numbers were correlated with the outcomes of progression-free survival (PFS) and overall survival.

RESULTS

After follow-up period of 0.8 to 152 months (median, 73), 25 patients (56%) were still alive. As continuous variables on univariate analysis, the predictors of PFS were patient age and absolute CD4 cell count (ACD4C), with the International Prognostic Index (IPI) marginally significant. Age was also a significant predictor of overall survival, and the IPI and ACD4C were marginally significant (P = .08). The 17 patients with a greater ACD4C (≥ 450/mm³) had better 5-year PFS than the 26 with a low ACD4C (88% vs. 50%; P = .02). Multivariable analysis, including age as a continuous variable, IPI group, and ACD4C of 450/mm³ showed that age and ACD4C were significant for PFS (P = .01 and P = .02, respectively).

CONCLUSION

Our data, although from a small series, suggest that the blood ACD4C might be a predictor of PFS for patients with DLBCL, independent of age and the IPI.

PASD1 promotes STAT3 activity and tumor growth by inhibiting TC45-mediated dephosphorylation of STAT3 in the nucleus

Activation of the transcription factor signal transducer and activator of transcription 3 (STAT3) is tightly regulated during various physiological processes, such as cell proliferation, survival, and differentiation, and aberrant STAT3 activation results in tumorigenesis. In this study, we identified the cancer/testis antigen PASD1 as a positive regulator of STAT3 activity. Overexpression of PASD1 activated STAT3 and potentiated IL-6-induced activation of STAT3, whereas knockdown of PASD1 had opposite effects. Endogenous coimmunoprecipitation experiments indicated that PASD1 interacted with STAT3 in the nucleus. Overexpression of PASD1 enhanced both basal and IL-6-induced STAT3 phosphorylation at Y705, whereas knockdown of PASD1 had opposite effects. Mechanistically, PASD1 competed with TC45, a nuclear protein tyrosine phosphatase, to associate with STAT3, thus inhibited TC45-mediated dephosphorylation of STAT3. Consistently, knockdown of PASD1 inhibited expression of many pro-oncogenic genes, leading to suppression of cell proliferation, anchorage-independent growth, cell migration, and tumor growth in nude mice. Our findings demonstrate that PASD1 serves as a critical nuclear positive regulator of STAT3-mediated gene expression and tumorigenesis.