POTE protein, a cancer-testis antigen, is highly expressed in spermatids in human testis and is associated with apoptotic cells

BESFA: bioinformatics based evolutionary, structural & functional analysis of prostrate, Placenta, Ovary, Testis, and Embryo (POTE) paralogs

The POTE family comprises 14 paralogues and is primarily expressed in Prostrate, Placenta, Ovary, Testis, Embryo (POTE), and cancerous cells. The prospective function of the POTE protein family under physiological conditions is less understood. We systematically analyzed their cellular localization and molecular docking analysis to elucidate POTE proteins' structure, function, and Adaptive Divergence. Our results suggest that group three POTE paralogs (POTEE, POTEF, POTEI, POTEJ, and POTEKP (a pseudogene)) exhibits significant variation among other members could be because of their Adaptive Divergence. Furthermore, our molecular docking studies on POTE protein revealed the highest binding affinity with NCI-approved anticancer compounds. Additionally, POTEE, POTEF, POTEI, and POTEJ were subject to an explicit molecular dynamic simulation for 50ns. MM-GBSA and other essential electrostatics were calculated that showcased that only POTEE and POTEF have absolute binding affinities with minimum energy exploitation. Thus, this study’s outcomes are expected to drive cancer research to successful utilization of POTE genes family as a new biomarker, which could pave the way for the discovery of new therapies.

N-Myristoylation by NMT1 Is POTEE-Dependent to Stimulate Liver Tumorigenesis via Differentially Regulating Ubiquitination of Targets

Background

A tremendous amount of studies have suggested that post-translational modifications (PTMs) play pivotal roles during tumorigenesis. Compared to other PTMs, lipid modification is less studied. Recently, N-myristoylation, one type of lipid modification, has been paid attention to the field of cancer. However, whether and how N-myristoylation exerts its roles in liver tumorigenesis still remains unclear.

Methods

Parallel reaction monitoring (PRM) was conducted to evaluate the expression of protein modification enzymes in paired tissues. Liver conditionally knocking NMT1 out mice model was used to assess the critical roles of N-myristoylation during liver tumorigenesis. Proteomics isobaric tags for relative and absolute quantification (iTraq) was performed to identify proteins that changed while NMT1 was knocked down. The click chemistry assay was used to evaluate the N-myristoylation levels of proteins.

Results

Here, N-myristolyation and its enzyme NMT1, but not NMT2, were found to be critical in liver cancer. Two categories of proteins, i.e., N-myristolyation down-regulated proteins (NDP, including LXN, RPL29, and FAU) and N-myristolyation up-regulated proteins (NUP, including AHSG, ALB, and TF), were revealed negatively and positively regulated by NMT1, respectively. Both NDP and NUP could be N-myristolyated by NMT1 indispensable of POTEE. However, N-myristolyation decreased and increased stability of NDP and NUP, respectively. Mechanistically, NDP-specific binding protein RPL7A facilitated HIST1H4H, which has ubiquitin E3 ligase function, to ubiquitinate NDP. By contrast, NUP-specific binding protein HBB prevented NUP from ubiquitination by HIST1H4H. Notably, function of RPL7A and HBB was all NMT1-dependent. Moreover, NDP suppressed while NUP stimulated transformative phenotypes. Clinically, higher levels of NMT1 and NUP with lower levels of NDP had worse prognostic outcome.

Conclusion

Collectively, N-myristolyation by NMT1 suppresses anti-tumorigenic NDP, whereas it stimulates pro-tumorigenic NUP by interfering their ubiquitination to finally result in a pro-tumorigenic outcome in liver cancer. Targeting N-myristolyation and NMT1 might be helpful to treat liver cancer.

Population-specific, recent positive directional selection suggests adaptation of human male reproductive genes to different environmental conditions

Background

Recent human transcriptomic analyses revealed a very large number of testis-enriched genes, many of which are involved in spermatogenesis. This comprehensive transcriptomic data lead us to the question whether positive selection was a decisive force influencing the evolution and variability of testis-enriched genes in humans. We used two methodological approaches to detect different levels of positive selection, namely episodic positive diversifying selection (i.e., past selection) in the human lineage within primate phylogeny, potentially driven by sperm competition, and recent positive directional selection in contemporary human populations, which would indicate adaptation to different environments.

Results

In the human lineage (after correction for multiple testing) we found that only the gene TULP2, for which no functional data are yet available, is subject to episodic positive diversifying selection. Using less stringent statistical criteria (uncorrected p-values), also the gene SPATA16, which has a pivotal role in male fertility and for which episodes of adaptive evolution have been suggested, also displays a putative signal of diversifying selection in the human branch. At the same time, we found evidence for recent positive directional selection acting on several human testis-enriched genes (MORC1, SLC9B1, ROPN1L, DMRT1, PLCZ1, RNF17, FAM71D and WBP2NL) that play important roles in human spermatogenesis and fertilization. Most of these genes are population-specifically under positive selection.

Conclusion

Episodic diversifying selection, possibly driven by sperm competition, was not an important force driving the evolution of testis-enriched genes in the human lineage. Population-specific, recent positive directional selection suggests an adaptation of male reproductive genes to different environmental conditions. Positive selection acts on eQTLS and sQTLs, indicating selective effects on important gene regulatory functions. In particular, the transcriptional diversity regulated by sQTLs in testis-enriched genes may be important for spermatocytes to respond to environmental and physiological stress.

Expression of the POTE gene family in human ovarian cancer

The POTE family includes 14 genes in three phylogenetic groups. We determined POTE mRNA expression in normal tissues, epithelial ovarian and high-grade serous ovarian cancer (EOC, HGSC), and pan-cancer, and determined the relationship of POTE expression to ovarian cancer clinicopathology. Groups 1 & 2 POTEs showed testis-specific expression in normal tissues, consistent with assignment as cancer-testis antigens (CTAs), while Group 3 POTEs were expressed in several normal tissues, indicating they are not CTAs. Pan-POTE and individual POTEs showed significantly elevated expression in EOC and HGSC compared to normal controls. Pan-POTE correlated with increased stage, grade, and the HGSC subtype. Select individual POTEs showed increased expression in recurrent HGSC, and POTEE specifically associated with reduced HGSC OS. Consistent with tumors, EOC cell lines had significantly elevated Pan-POTE compared to OSE and FTE cells. Notably, Group 1 & 2 POTEs (POTEs A/B/B2/C/D), Group 3 POTE-actin genes (POTEs E/F/I/J/KP), and other Group 3 POTEs (POTEs G/H/M) show within-group correlated expression, and pan-cancer analyses of tumors and cell lines confirmed this relationship. Based on their restricted expression in normal tissues and increased expression and association with poor prognosis in ovarian cancer, POTEs are potential oncogenes and therapeutic targets in this malignancy.

Down-regulation of POTEG predicts poor prognosis in esophageal squamous cell carcinoma patients

POTE ankyrin domain family, member G (poteg) belongs to POTE family. The POTE family is composed of many proteins which are very closely related and expressed in prostate, ovary, testis, and placenta. Some POTE paralogs are related with some cancers. Here we showed that down‐regulation of POTEG was detected in about 60% primary esophageal squamous cell carcinoma (ESCC) tumor tissues. Clinical association studies determined that POTEG down‐regulation was significantly correlated with tumor differentiation, lymph nodes metastasis and TNM staging. Kaplan‐Meier analysis determined that POTEG down‐regulation was associated with poorer clinical outcomes of ESCC patients (P = 0.026). Functional studies showed that POTEG overexpression could suppress tumor cell growth and metastasis capacity in vitro and in vivo. Molecular analyses revealed that POTEG downregulated CDKs, leading to subsequent inhibition of Rb phosphorylation, and consequently arrested Cell Cycle at G1/S Checkpoint. POTEG overexpression induced apoptosis by activating caspases and PARP, and regulating canonical mitochondrial apoptotic pathways. On the other side, POTEG inhibited epithelial‐mesenchymal transition and suppressed tumor cell metastasis. In conclusion, our study reveals a functionally important control mechanism of POTEG in esophageal cancer pathogenesis, suggesting potential use in the ESCC intervention and therapeutic strategies.

Androgen-induced lncRNA POTEF-AS1 regulates apoptosis-related pathway to facilitate cell survival in prostate cancer cells

Although long non‐coding RNAs (lncRNAs) have been associated with a variety of cancers, the interplay between lncRNAs and androgen receptor signaling in prostate cancer is still unclear. We identified an androgen‐dependent lncRNA, POTEF‐AS1, whose expression was regulated by androgen receptor in two androgen‐dependent cells by using directional RNA sequencing analysis. POTEF‐AS1 promoted cell growth, repressed genes related to the Toll‐like receptor signaling and apoptosis pathways, and inhibited apoptosis in docetaxel‐treated LNCaP cells. These findings suggest that POTEF‐AS1 would play a key role in the progression of prostate cancer by repressing Toll‐like receptor signaling.

Serum levels of the cancer-testis antigen POTEE and its clinical significance in non-small-cell lung cancer

Background

POTEE (POTE ankyrin domain family, member E) is a newly identified cancer-testis antigen that has been found to be expressed in a wide variety of human cancers including cancers of the colon, prostate, lung, breast, ovary, and pancreas.

Aim

To measure the serum levels of POTEE in patients with non-small-cell lung cancer (NSCLC) and to explore the clinical significance of POTEE in NSCLC.

Patients and Methods

104 NSCLC patients, 66 benign lung disease patients and 80 healthy volunteers were enrolled in this study from May 2013 to February 2014. Serum POTEE levels were measured using enzyme-linked immunosorbent assay (ELISA). Numerical variables were recorded as means ± standard deviation (SD) and analyzed by independent t tests. Categorical variables were calculated as rates and were analyzed using a χ² test or Fisher’s exact test. Survival curves were estimated and compared using the Kaplan-Meier method and log-rank tests.

Results

Serum POTEE levels were significantly higher in NSCLC patients than in benign lung disease patients and healthy controls (mean ± SD [pg/ml], 324.38± 13.84 vs. 156.93 ± 17.38 and 139.09 ± 15.80, P<0.001) and were significantly correlated with TNM stage. Survival analysis revealed that patients with low serum POTEE had longer progression-free survival (PFS) than those with high serum POTEE (P=0.021). Cox multivariate analysis indicated that POTEE was an independent prognostic factor of progression-free survival (P =0.009, hazard ratio, 2.440).

Conclusions

Serum POTEE level in NSCLC patients is associated with TNM stage and is a potential prognostic factor.

The C-terminal common to group 3 POTES (CtG3P): a newly discovered nucleolar marker associated with malignant progression and metastasis

A gene family expressed in prostate, ovary, testis and placenta (POTEs) is newly defined and primate-specific. POTE genes have 13 paralogs, which are dispersed in 8 chromosomes and divided into three groups. The proteins encoded by these genes contain three domains: An N-terminal, ankyrin repeats and a C-terminus. Previous studies suggest that POTE proteins are localized in the inner aspect of cellular membrane and are considered as cancer-testis antigens, because they expressed widely in cancers, but in limited benign tissues. In this study, we will study the subcellular distribution of all POTE proteins and their associations with the progress and metastasis of malignancies. By performing Immunohistochemistry, Immunocytochemistry and immunofluorescence assay on tissue microarray slides containing tissues with different pathology and origins or on cell lines, we found that the epitopes of N- and C-terminals of all detected POTEs were widely expressed in benign and malignant tissues. Among these epitopes, C-terminal common to group 3 POTEs (CtG3P) was the only portion localized in nucleoli. The nucleolar IHC scores for CtG3P was lowest in benign tissues (4.47 ± 3.43), significantly higher in localized malignancies (5.32 ± 3.36, p = 3.63E-02), and highest in metastatic malignancies (7.90 ± 2.29, p = 8.13E-12). The CtG3P was better in differentiation of benign from malignant changes, and/or in differentiation of localized from metastatic cancers as compared with Ki-67 and AgNORs. In addition, transient transfection of siRNA against mRNA of group 3 POTEs influences the growth and survival of MCF-7 cells in vitro in a dose dependent manner.