Frequent PD-L1 expression in primary and metastatic penile squamous cell carcinoma: potential opportunities for immunotherapeutic approaches.

BACKGROUND: Despite aggressive multimodal therapy, locally advanced and/or metastatic penile squamous cell carcinoma (SqCC) is associated with significant morbidity and mortality, indicating a need for new therapeutic options. Given the emerging clinical utility of immunotherapeutics, we sought to assess the incidence and potential clinical significance of PD-L1 expression in penile SqCC. PATIENTS AND METHODS: Using an anti-PD-L1 primary antibody (clone 5H1), immunohistochemistry was carried out on whole tumor sections from 37 patients with penile SqCC treated at our institution between 2005 and 2013. PD-L1-positive tumors were defined as those with membranous staining in ≥5% of tumor cells. Association between PD-L1 expression and clinicopathologic parameters was examined using Fisher's exact test. Correlation between PD-L1 expression in primary tumors and matched metastases was assessed using the Spearman rank correlation coefficient (ρ). The difference in cancer-specific mortality between PD-L1-positive and -negative groups was examined using the log-rank test. RESULTS: Twenty-three (62.2%) of 37 primary tumors were positive for PD-L1 expression, and there was strong positive correlation of PD-L1 expression in primary and metastatic samples (ρ = 0.72; 0.032 < P < 0.036). Primary tumor PD-L1 expression was significantly associated with usual type histology (P = 0.040) and regional lymph node metastasis (P = 0.024), as well as decreased cancer-specific survival (P = 0.011). CONCLUSIONS: The majority of primary penile SqCC tumors express PD-L1, which is associated with high-risk clinicopathologic features and poor clinical outcome. These data provide a rational basis for further investigation of anti-PD-1 and anti-PD-L1 immunotherapeutics in patients with advanced penile SqCC.

Management of patients with advanced prostate cancer: recommendations of the St Gallen Advanced Prostate Cancer Consensus Conference (APCCC) 2015.

The first St Gallen Advanced Prostate Cancer Consensus Conference (APCCC) Expert Panel identified and reviewed the available evidence for the ten most important areas of controversy in advanced prostate cancer (APC) management. The successful registration of several drugs for castration-resistant prostate cancer and the recent studies of chemo-hormonal therapy in men with castration-naïve prostate cancer have led to considerable uncertainty as to the best treatment choices, sequence of treatment options and appropriate patient selection. Management recommendations based on expert opinion, and not based on a critical review of the available evidence, are presented. The various recommendations carried differing degrees of support, as reflected in the wording of the article text and in the detailed voting results recorded in supplementary Material, available at Annals of Oncology online. Detailed decisions on treatment as always will involve consideration of disease extent and location, prior treatments, host factors, patient preferences as well as logistical and economic constraints. Inclusion of men with APC in clinical trials should be encouraged.

The inhibition of pro-apoptotic ICE-like proteases enhances HIV replication.

Accelerated programmed cell death, or apoptosis, contributes to the CD4+ T-cell depletion characteristic of infection by human immunodeficiency virus (HIV). It has therefore been proposed that limiting apoptosis may represent a therapeutic modality for HIV infection. We found, however, that T leukemia cells or peripheral blood mononuclear cells (PBMCs) exposed to HIV-1 underwent enhanced viral replication in the presence of the cell death inhibitor, N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (z-AVD-fmk). Furthermore, z-VAD-fmk, which targets the pro-apoptotic interleukin-1 beta-converting enzyme (ICE)-like proteases, stimulated endogenous virus production in activated PBMCs derived from HIV-1-infected asymptomatic individuals. These findings suggest that programmed cell death may serve as a beneficial host mechanism to limit HIV spread and that strategies to inhibit it may have deleterious consequences for the infected host.

Interaction of CED-4 with CED-3 and CED-9: a molecular framework for cell death.

Previous genetic studies of the nematode Caenorhabditis elegans identified three important components of the cell death machinery. CED-3 and CED-4 function to kill cells, whereas CED-9 protects cells from death. Here CED-9 and its mammalian homolog Bcl-xL (a member of the Bcl-2 family of cell death regulators) were both found to interact with and inhibit the function of CED-4. In addition, analysis revealed that CED-4 can simultaneously interact with CED-3 and its mammalian counterparts interleukin-1beta-converting enzyme (ICE) and FLICE. Thus, CED-4 plays a central role in the cell death pathway, biochemically linking CED-9 and the Bcl-2 family to CED-3 and the ICE family of pro-apoptotic cysteine proteases.

The receptor for the cytotoxic ligand TRAIL.

TRAIL (also known as Apo-2L) is a member of the tumor necrosis factor (TNF) ligand family that rapidly induces apoptosis in a variety of transformed cell lines. The human receptor for TRAIL was found to be an undescribed member of the TNF-receptor family (designated death receptor-4, DR4) that contains a cytoplasmic "death domain" capable of engaging the cell suicide apparatus but not the nuclear factor kappa B pathway in the system studied. Unlike Fas, TNFR-1, and DR3, DR4 could not use FADD to transmit the death signal, suggesting the use of distinct proximal signaling machinery. Thus, the DR4-TRAIL axis defines another receptor-ligand pair involved in regulating cell suicide and tissue homeostasis.

Signal transduction by DR3, a death domain-containing receptor related to TNFR-1 and CD95.

Tumor necrosis factor receptor-1 (TNFR-1) and CD95 (also called Fas or APO-1) are cytokine receptors that engage the apoptosis pathway through a region of intracellular homology, designated the "death domain." Another death domain-containing member of the TNFR family, death receptor 3 (DR3), was identified and was shown to induce both apoptosis and activation of nuclear factor kappaB. Expression of DR3 appears to be restricted to tissues enriched in lymphocytes. DR3 signal transduction is mediated by a complex of intracellular signaling molecules including TRADD, TRAF2, FADD, and FLICE. Thus, DR3 likely plays a role in regulating lymphocyte homeostasis.

Role of epidermal growth factor receptor degradation in gemcitabine-mediated cytotoxicity.

We have recently reported that treatment with gemcitabine, a potent chemotherapeutic agent and radiation sensitizer, stimulates phosphorylation of the epidermal growth factor receptor (EGFR). Because phosphorylation of EGFR is known to precede receptor degradation, we hypothesized that gemcitabine treatment may also result in EGFR degradation. In two human head and neck cancer cell lines, UMSCC-1 and UMSCC-6, we demonstrated an approximately 80% decrease in total EGFR levels at 72 h after a 2-h treatment with 1 muM gemcitabine. Neither cisplatin nor 5-fluorouracil, which are used to treat head and neck cancer, caused EGFR degradation. EGFR downregulation did not occur at the level of transcription, as assessed by reverse transcription-polymerase chain reaction (RT-PCR), but instead occurred via phosphorylation and ubiquitination of the receptor along a proteosome/lysosome-mediated pathway. Inhibition of EGFR degradation, by either pretreatment with the EGFR tyrosine kinase inhibitor gefitinib or by exposure to the proteosome/lysosome inhibitor MG132, significantly reduced gemcitabine-induced cell death. These results suggest that EGFR degradation may be a novel mechanism for gemcitabine-mediated cell death. These findings also indicate that caution should be exercised when combining gemcitabine with agents that may prevent EGFR degradation, such as EGFR tyrosine kinase inhibitors administered in a suboptimal sequence or proteosome inhibitors.

TMPRSS2:ERG gene fusion associated with lethal prostate cancer in a watchful waiting cohort.

The identification of the TMPRSS2:ERG fusion in prostate cancer suggests that distinct molecular subtypes may define risk for disease progression. In surgical series, TMPRSS2:ERG fusion was identified in 50% of the tumors. Here, we report on a population-based cohort of men with localized prostate cancers followed by expectant (watchful waiting) therapy with 15% (17/111) TMPRSS2:ERG fusion. We identified a statistically significant association between TMPRSS2:ERG fusion and prostate cancer specific death (cumulative incidence ratio=2.7, P<0.01, 95% confidence interval=1.3-5.8). Quantitative reverse-transcription-polymerase chain reaction demonstrated high ets-related [corrected] gene (ERG) expression to be associated with TMPRSS2:ERG fusion (P<0.005). These data suggest that TMPRSS2:ERG fusion prostate cancers may have a more aggressive phenotype, possibly mediated through increased ERG expression.

The cell-death machine.

Apoptosis, or programmed cell death, is the physiological process whereby individual cells are deliberately eliminated to achieve homeostasis and proper metazoan development. Numerous genes have recently been identified that are involved in apoptosis: some are believed to encode death effectors, whereas others encode positive or negative regulators of the cell-death machine. Precisely how these various proteins interact in the molecular mechanism of apoptosis remains to be discovered.

Cytotoxic T-cell-derived granzyme B activates the apoptotic protease ICE-LAP3.

Cytotoxic T lymphocytes (CTLs) and natural killers (NK) cells provide immune surveillance against viruses and neoplasms, and play a central role in the pathogenesis of autoimmune disease, AIDS and graft rejection. Thus, it is important to understand the precise molecular mechanism(s) whereby cytotoxic lymphocytes destroy susceptible target cells. Granule-mediated cytotoxicity requires a combination of both perforin and granzyme B. Perforin polymerizes to form transmembrane channels and presumably allows granzyme B access to target cell substrates, which until recently, were unknown. One clue to the identity of the physiological substrate(s) activated by granzyme B comes from its unusual specificity for cleaving synthetic substrates after aspartate residues. Members of the ICE/CED-3 family of cysteine proteases are prime candidates as they are important apoptotic effectors and are expressed as zymogens, which can be processed to form active heterodimeric enzymes after cleavage at specific aspartate residues. Previous studies have shown that granzyme B proteolytically activates the cell death effector Yama/CPP32/apopain (referred to here as Yama). Here we report that granzyme B also activates ICE-LAP3/Mch3/CMH-1 (referred to here as ICE-LAP3), which, along with Yama and Mch2, forms a subset of the ICE/CED-3 family of cysteine proteases most closely related to the Caenorhabditis elegans cell death gene, CED-3. Importantly, Jurkat T cells incubated with granzyme B and a sublytic concentration of perforin undergo apoptosis, which is preceded by the activation of endogenous ICE-LAP3. Thus, we propose that granzyme B mediates apoptosis by directly engaging the target cell's death effector machinery, which is probably composed of an arsenal of intracellular, CED-3-like cysteine proteases.

Profiling of cancer cells using protein microarrays: discovery of novel radiation-regulated proteins.

The advent of DNA microarray technology will likely have a major impact on the molecular classification and understanding of human cancer. Obtaining a global perspective of proteins expressed in cancer cells is considerably more challenging. Here we describe a microarray-based platform that can be used to measure protein levels and activities in a complex biological milieu such as a cellular lysate. Using a protein microarray made up of 1920 elements (146 distinct antibodies) we were able to monitor alterations of protein levels in LoVo colon carcinoma cells treated with ionizing radiation. The protein microarray approach revealed radiation-induced up-regulation of apoptotic regulators including p53, DNA fragmentation factor 40/caspase activated DNase, DNA fragmentation factor 45/inhibitor of caspase activated DNase, tumor necrosis factor-related apoptosis-inducing ligand, death receptor 5, decoy receptor 2, FLICE-like inhibitory protein, signal transducers and activators of transcription 1alpha, and uncoupling protein 2, among others. Consistent with this observation, an increased percentage of apoptosis was observed in irradiated LoVo cells. Interestingly, we also observed radiation-induced down-regulation of carcinoembryonic antigen, a prototypic cancer biomarker. Selected proteins assessed by microarray were validated by traditional immunoblotting. Taken together, our work suggests that protein/antibody microarrays will facilitate high-throughput proteomic studies of human cancer and carcinogenesis.

MicroRNA-101 regulated transcriptional modulator SUB1 plays a role in prostate cancer.

MicroRNA-101, a tumor suppressor microRNA (miR), is often downregulated in cancer and is known to target multiple oncogenes. Some of the genes that are negatively regulated by miR-101 expression include histone methyltransferase EZH2 (enhancer of zeste homolog 2), COX2 (cyclooxygenase-2), POMP (proteasome maturation protein), CERS6, STMN1, MCL-1 and ROCK2, among others. In the present study, we show that miR-101 targets transcriptional coactivator SUB1 homolog (Saccharomyces cerevisiae)/PC4 (positive cofactor 4) and regulates its expression. SUB1 is known to have diverse role in vital cell processes such as DNA replication, repair and heterochromatinization. SUB1 is known to modulate transcription and acts as a mediator between the upstream activators and general transcription machinery. Expression profiling in several cancers revealed SUB1 overexpression, suggesting a potential role in tumorigenesis. However, detailed regulation and function of SUB1 has not been elucidated. In this study, we show elevated expression of SUB1 in aggressive prostate cancer. Knockdown of SUB1 in prostate cancer cells resulted in reduced cell proliferation, invasion and migration in vitro, and tumor growth and metastasis in vivo. Gene expression analyses coupled with chromatin immunoprecipitation revealed that SUB1 binds to the promoter regions of several oncogenes such as PLK1 (Polo-like kinase 1), C-MYC, serine-threonine kinase BUB1B and regulates their expression. Additionally, we observed SUB1 downregulated CDKN1B expression. PLK1 knockdown or use of PLK1 inhibitor can mitigate oncogenic function of SUB1 in benign prostate cancer cells. Thus, our study suggests that miR-101 loss results in increased SUB1 expression and subsequent activation of known oncogenes driving prostate cancer progression and metastasis. This study therefore demonstrates functional role of SUB1 in prostate cancer, and identifies its regulation and potential downstream therapeutic targets of SUB1 in prostate cancer.

CD95 (APO-1/Fas) induces activation of SAP kinases downstream of ICE-like proteases.

Triggering of CD95 (APO-1/Fas) on different T- and B-cell lines resulted in the induction of a number of kinases (35 kDa, 38 kDa, 46 kDa and 54 kDa) that phosphorylate c-Jun and to a lesser extent Histone H1. Activation of these kinases was independent of protein biosynthesis and preceded apoptotic DNA degradation. The kinase activation pattern was specific for CD95 triggering since a variety of physical or chemical inducers of T- and B-cell apoptosis activated different kinases. The kinase activities at 46 and 54 kDa contained members of the stress-activated family of protein kinases (JNK/SAPK). Activation of the CD95-specific set of kinases was prevented by treating cells with the ICE-inhibiting peptide N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD-fmk) or by overexpression of the cow pox virus serpin CrmA. However, despite inhibition of ICE-like proteases the death signal was readily initiated at the cell membrane since a CD95 death-inducing signaling complex (DISC) was formed. Thus, our results demonstrate that ICE-like proteases in the CD95 pathway function downstream of the DISC but upstream of SAP kinases.

CD95 (APO-1/Fas)-associating signalling proteins.

The CD95 (APO-1/Fas) receptor has attracted great interest in recent years because it transduces an apoptotic signal in a variety of different tissues. CD95 belongs to the NGF/TNF-receptor superfamily, members of which need to be trimerized by specific protein ligands in order to generate a signal. This review focuses on recent advances in the understanding of the proximal signal transduction mechanism of CD95. The cloning of numerous proteins that interact with CD95 and other members of this receptor family and the in vivo identification of several proteins that associate with CD95 in a ligand-dependent fashion opens the way to delineate the death pathway and to explain crosstalk among these receptors on a molecular basis.

The apoptosome: heart and soul of the cell death machine.

Apoptosis is a fundamental biologic process by which metazoan cells orchestrate their own self-demise. Genetic analyses of the nematode C elegans identified three core components of the suicide apparatus which include CED-3, CED-4, and CED-9. An analogous set of core constituents exists in mammalian cells and includes caspase-9, Apaf-1, and bcl-2/xL, respectively. CED-3 and CED-4, along with their mammalian counterparts, function to kill cells, whereas CED-9 and its mammalian equivalents protect cells from death. These central components biochemically intermingle in a ternary complex recently dubbed the "apoptosome." The C elegans protein EGL-1 and its mammalian counterparts, pro-apoptotic members of the bcl-2 family, induce cell death by disrupting apoptosome interactions. Thus, EGL-1 may represent a primordial signal integrator for the apoptosome. Various biochemical processes including oligomerization, adenosine triphosphate ATP/dATP binding, and cytochrome c interaction play a role in regulating the ternary death complex. Recent studies suggest that cell death receptors, such as CD95, may amplify their suicide signal by activating the apoptosome. These mutual associations by core components of the suicide apparatus provide a molecular framework in which diverse death signals likely interface. Understanding the apoptosome and its cellular connections will facilitate the design of novel therapeutic strategies for cancer and other disease states in which apoptosis plays a pivotal role.

A novel approach to biomarker discovery in head and neck cancer using an autoantibody signature.

Despite the dismal prognosis for patients with squamous cell carcinoma of the head and neck (SCCHN), there have been no novel treatments in over 40 years. Identification of novel tumor antigens in SCCHN will facilitate the identification of potential novel treatment targets. Tumor antigens are proteins selectively expressed by tumor cells and recognized by the host immune system. Phage-displayed tumor antigens were enriched by biopanning with normal and then SCCHN-specific serum. Ninety-six phage clones were sequenced for identification, and 21 clones were validated using Luminex. One of these proteins, L23, a novel tumor antigen in SCCHN, was validated as an oncogene. L23 is upregulated in SCCHN compared with normal keratinocytes. Knockdown of L23 inhibited proliferation, invasion and cell survival. Overexpression of L23 had the reverse effect. Overexpression of L23 in non malignant cells led to transformation. Injection of SCCHN cells with knockdown of L23 in mice, induced tumors that were significantly smaller than control tumors. In conclusion, the immunomic screen yielded a panel of antigens specific to SCCHN; one of these proteins, L23, is a novel oncogene in SCCHN.

The tumor suppressor gene rap1GAP is silenced by miR-101-mediated EZH2 overexpression in invasive squamous cell carcinoma.

Rap1GAP is a critical tumor suppressor gene that is downregulated in multiple aggressive cancers, such as head and neck squamous cell carcinoma, melanoma and pancreatic cancer. However, the mechanistic basis of rap1GAP downregulation in cancers is poorly understood. By employing an integrative approach, we demonstrate polycomb-mediated repression of rap1GAP that involves Enhancer of Zeste Homolog 2 (EZH2), a histone methyltransferase in head and neck cancers. We further demonstrate that the loss of miR-101 expression correlates with EZH2 upregulation, and the concomitant downregulation of rap1GAP in head and neck cancers. EZH2 represses rap1GAP by facilitating the trimethylation of histone 3 at lysine 27, a mark of gene repression, and also hypermethylation of rap1GAP promoter. These results provide a conceptual framework involving a microRNA-oncogene-tumor suppressor axis to understand head and neck cancer progression.