Detection of melanoma-derived cancer-testis antigen CT16 in patient sera by a novel immunoassay

Melanoma-associated cancer-testis antigen 16 (CT16) regulates the expression of apoptotic and antiapoptotic genes and promotes cell survival

Cancer-testis (CT) antigens are predominantly expressed in testis or placenta, but absent in most adult tissues. During malignant transformation CT genes are often activated. CT antigen 16 (CT16, PAGE5) is frequently expressed in advanced melanoma but its biological function has been unknown. To examine the role of CT16 in cell survival we knocked it down in A2058 melanoma cells using specific siRNAs and exposed the cells to cancer drug cisplatin known to induce apoptosis. As a result, cell survival was markedly decreased. To study the effects of CT16 on cell survival in more detail, the cellular gene expression profiles were investigated after CT16 silencing in CT16 positive A2058 melanoma cells, as well as after CT16 overexpression in CT16 negative WM-266-4 melanoma cells. Among the 11 genes both upregulated by CT16 silencing and downregulated by CT16 overexpression or vice versa, 4 genes were potentially apoptotic or antiapoptotic genes. CT16 was recognized as a positive regulator of antiapoptotic metallothionein 2A and interleukin 8 genes, whereas it inhibited the expression of apoptosis inducing dickkopf 1 (DKK1) gene. In addition CT16 enhanced the expression of fatty acid binding protein 7, a known promoter of melanoma progression. The effect of CT16 on DKK1 expression was p53 independent. Furthermore, CT16 did not regulate apoptotic genes via DNA methylation. In twenty melanoma metastasis tissue samples average DKK1 mRNA level was shown to be significantly (p<0.05) lower in high CT16 expressing tumors (n = 3) when compared to the tumors with low CT16 expression (n = 17). Thus, our results indicate that CT16 promotes the survival of melanoma cells and is therefore a potential target for future drug development.

Peptide Vaccine Therapy in Colorectal Cancer

Colorectal cancer is the third most common cause of cancer-related deaths and the second most prevalent (after breast cancer) in the western world. High metastatic relapse rates and severe side effects associated with the adjuvant treatment have urged oncologists and clinicians to find a novel, less toxic therapeutic strategy. Considering the limited success of the past clinical trials involving peptide vaccine therapy to treat colorectal cancer, it is necessary to revise our knowledge of the immune system and its potential use in tackling cancer. This review presents the efforts of the scientific community in the development of peptide vaccine therapy for colorectal cancer. We review recent clinical trials and the strategies for immunologic monitoring of responses to peptide vaccine therapy. We also discuss the mechanisms underlying the therapy and potential molecular targets in colon cancer.

Characterization of intrinsically disordered prostate associated gene (PAGE5) at single residue resolution by NMR spectroscopy

Background

The Cancer-Testis antigens (CTA) are proteins expressed in human germ line and certain cancer cells. CTAs form a large gene family, representing 10% of X-chromosomal genes. They have high potential for cancer-specific immunotherapy. However, their biological functions are currently unknown. Prostate associated genes (PAGE) are characterized as CTAs. PAGE5 is one of six proteins belonging to this protein family, also called CT16.

Methodology/Principal findings

In this study we show, using bioinformatics, chromatographic and solution state NMR spectroscopic methods, that PAGE5 is an intrinsically disordered protein (IDP).

Conclusion/Significance

The study stands out as the first time structural characterization of the PAGE family protein and introduces how solution state NMR spectroscopy can be effectively utilized for identification of molecular recognition regions (MoRF) in IDPs, known often as transiently populated secondary structures.

Neuropilin-2: a novel biomarker for malignant melanoma?

Neuropilin-2, a cell surface receptor involved in angiogenesis and axonal guidance, has recently been shown to be a critical mediator of tumor-associated lymphangiogenesis. Given that lymphangiogenesis is a major conduit of metastasis in melanomas and that blocking neuropilin-2 function in vivo is effective in inhibiting tumor cell metastasis, we sought to determine the clinical relevance of neuropilin-2 expression in cutaneous melanoma. Immunohistochemical analysis of neuropilin-2 expression was evaluated in nevomelanocytic proliferations that included a tissue microarray and histologic sections from samples of primary melanomas (n = 42; 40 for tissue microarray, 2 for histologic sections), metastatic melanomas (n = 30; 22 for tissue microarray, 8 for histologic sections), and nevi (n = 30; 5 for tissue microarray, 25 for histologic sections), as well as a panel of normal human tissues and select nonmelanocytic tumors. Staining for grading and intensity of neuropilin-2 expression was estimated semiquantitatively as follows for the former: less than 20%, 20% to 60%, and more than 60% of tissue present, and for the latter from 0 to 3, with 3 being the highest and 0 the lowest intensity. In nevomelanocytic proliferations, more than 20% staining for neuropilin-2 was noted in 36 (86%) of 42 cases of primary melanoma, in 27 (90%) of 30 cases of metastatic melanoma, and in 9 (30%) of 30 cases of nevi with differences achieving statistical significance between melanoma (primary and metastatic) and nevi (P < .0001). For staining intensity, an intensity of 2 or more was noted in 36 (86%) of 42 cases of primary melanoma, in 17 (57%) of 30 cases of metastatic melanoma and in 7 (30%) of 23 cases of nevi, with differences achieving statistical significance between melanoma (primary and metastatic) and nevi (P < .0001). In normal human tissue, consistently strong neuropilin-2 staining was noted in kidney (glomerular endothelial cells, collecting tubules, and collecting ducts), skin (epidermal keratinocytes), and testes (epithelium of the seminiferous tubules), whereas in tumoral tissue, consistently strong staining was noted only in renal cell carcinoma but not in any of the other tumors studied. More recently, using a heterotypic coculture methodology with melanoma and endothelial cells, we have demonstrated successful up-regulation of neuropilin-2 and confirmed the critical role of neuropilin-2 in melanoma-endothelial interactions. Because these coculture methods were developed to model melanoma metastasis, the significantly increased and enhanced expression of neuropilin-2 staining in primary and metastatic melanoma versus nevi in the current study suggests that it is also relevant in vivo.

Extension of the HA-detection based approach: (HCA)CON(CA)H and (HCA)NCO(CA)H experiments for the main-chain assignment of intrinsically disordered proteins

Extensive resonance overlap exacerbates assignment of intrinsically disordered proteins (IDPs). This issue can be circumvented by utilizing (15)N, (13)C' and (1)H(N) spins, where the chemical shift dispersion is mainly dictated by the characteristics of consecutive amino acid residues. Especially (15)N and (13)C' spins offer superior chemical shift dispersion in comparison to (13)C(α) and (13)C(β) spins. However, HN-detected experiments suffer from exchange broadening of amide proton signals on IDPs especially under alkali conditions. To that end, we propose here two novel HA-detected experiments, (HCA)CON(CA)H and (HCA)NCO(CA)H and a new assignment protocol based on panoply of unidirectional HA-detected experiments that enable robust backbone assignment of IDPs also at high pH. The new approach was tested at pH 6.5 and pH 8.5 on cancer/testis antigen CT16, a 110-residue IDP, and virtually complete backbone assignment of CT16 was obtained by employing the novel HA-detected experiments together with the previously introduced iH(CA)NCO scheme. Remarkably, also those 10 N-terminal residues that remained unassigned in our earlier HN-detection based assignment approach even at pH 6.5 were now readily assigned. Moreover, theoretical calculations and experimental results suggest that overall sensitivity of the new experiments is also applicable to small or medium sized globular proteins that require alkaline conditions.