Function and regulation of Rab GTPases in cancers.

The Rab small GTPases are characterized by the distinct intracellular localization and modulate various endocytic, transcytic and exocytic transport pathways. Rab proteins function as scaffolds that connect signaling pathways and intracellular membrane trafficking processes through the recruitment of effectors, such as tethering factors, phosphatases, motors and kinases. In different cancers, Rabs play as either an onco-protein or a tumor suppressor role, highly dependending on the context. The molecular mechanistic research has revealed that Rab proteins are involved in cancer progression through influences on migration, invasion, metabolism, exosome secretion, autophagy, and drug resistance of cancer cells. Therefore, targeting Rab GTPases to recover the dysregulated vesicle transport systems may provide potential strategy to restrain cancer progression. In this review, we discuss the regulation of Rab protein level and activity in modulating pathways involved in tumor progression, and propose that Rab proteins may serve as a prognostic factor in different cancers.

Intact glycopeptides identified by LC-MS/MS as biomarkers for response to chemotherapy of locally advanced cervical cancer.

Objective: For locally advanced cervical cancer (LACC), patients who respond to chemotherapy have a potential survival advantage compared to nonresponsive patients. Thus, it is necessary to explore specific biological markers for the efficacy of chemotherapy, which is beneficial to personalized treatment. Methods: In the present study, we performed a comprehensive screening of site-specific N-glycopeptides in serum glycoproteins to identify glycopeptide markers for predicting the efficacy of chemotherapy, which is beneficial to personalized treatment. In total, 20 serum samples before and after neoadjuvant chemotherapy (NACT) from 10 LACC patients (NACT response, n=6) and NACT nonresponse, n=4) cases) were analyzed using LC-MS/MS, and 20 sets of mass spectrometry (MS) data were collected using liquid chromatography coupled with high-energy collisional dissociation tandem MS (LC-HCD-MS/MS) for quantitative analysis on the novel software platform, Byos. We also identified differential glycopeptides before and after chemotherapy in chemo-sensitive and chemo-resistant patients. Results: In the present study, a total of 148 glycoproteins, 496 glycosylation sites and 2279 complete glycopeptides were identified in serum samples of LACC patients. Before and after chemotherapy, there were 13 differentially expressed glycoproteins, 654 differentially expressed glycopeptides and 93 differentially expressed glycosites in the NACT responsive group, whereas there were 18 differentially expressed glycoproteins, 569 differentially expressed glycopeptides and 99 differentially expressed glycosites in the NACT nonresponsive group. After quantitative analysis, 6 of 570 glycopeptides were identified as biomarkers for predicting the sensitivity of neoadjuvant chemotherapy in LACC. The corresponding glycopeptides included MASP1, LUM, ATRN, CO8A, CO8B and CO6. The relative abundances of the six glycopeptides, including MASP1, LUM, ATRN, CO8A, CO8B and CO6, were significantly higher in the NACT-responsive group and were significantly decreased after chemotherapy. High levels of these six glycopeptides may indicate that chemotherapy is effective. Thus, these glycopeptides are expected to serve as biomarkers for predicting the efficacy of neoadjuvant chemotherapy in locally advanced cervical cancer. Conclusion: The present study revealed that the N-glycopeptide of MASP1, LUM, ATRN, CO8A, CO8B and CO6 may be potential biomarkers for predicting the efficacy of chemotherapy for cervical cancer.

PUS1 is a novel biomarker for evaluating malignancy of human renal cell carcinoma.

Renal cell carcinoma (RCC) is one of the most common malignancies. Despite the rapid development of the oncology research and surgical treatment, the prognosis of RCC has not significantly improved. Thus, exploration of the pathological molecular mechanism and development of new therapeutic targets of RCC are of great importance. Herein, by bioinformatic analysis and in vitro cell experiments, we report that, the expression of pseudouridine synthase 1 (PUS1), belonging to the family of PUS enzymes that participate in RNA modifications, is closely associated with RCC progression. In addition, the upregulated PUS1 expression results in the elevated RCC cancer cell viability, migration, invasion and colony formation ability, whereas the decreased PUS1 expression exerts the opposite effects on RCC cells. Thus, our findings show the potential role of PUS1 in RCC cells, providing with evidence that PUS1 is involved in RCC progression, which may help contribute to RCC diagnosis and intervention in clinic.

ALKBH1 contributes to renal cell carcinoma progression by reducing N6-methyladenine of GPR137.

BACKGROUND: Renal cell carcinoma (RCC) accounts for approximately 4% of all adult malignancies with high mortality worldwide. Although conventional chemotherapy and radiotherapy treatment has been applied for RCC in clinic, the mortality rate of patients is increasing each year, and patients with metastatic RCC are still suffering from poor prognosis. Thus, further investigation of the molecular mechanisms responsible for the development and progression of RCC is of particular importance. METHODS: Total of 10 pairs of RCC tissues and adjacent nontumor tissues were collected for examination of ALKBH1 and GPR137 expression. The correlations between ALKBH1 and GPR137 expression in RCC patient were assessed by GEPIA online tool and were analyzed using auto best cutoff. The human RCC cell lines Caki-1, 786-O, ACHN, Osrc2, A498, and 769-P, were used for mechanistic investigation. RESULTS: Here, we report that the expression of AlkB homologue 1 (ALKBH1) is upregulated in RCC tissues, which is correlated with G-protein-coupled receptor 137 (GPR137) expression. The elevated expression of ALKBH1 is associated with RCC cell malignant characteristics, including cell proliferation and movement (migration and invasion). Mechanistic investigation further reveals that ALKBH1 reduces m6 A levels of GPR137 mRNA in RCC cells, which upregulates GPR137 mRNA levels, resulting in the increased GPR137 protein expression subsequently and the enhanced RCC cell biological actions consequently. In contrast, the suppression of GPR137 effectively alleviates the ALKBH1-induced malignancies of RCC cells. CONCLUSION: Our results indicate that ALKBH1-GPR137 axis might be used as a potential therapeutic target in RCC, contributing to finding new prognostic biomarkers for RCC at an early stage.

Circulating tumor DNA as a prognostic marker in high-risk endometrial cancer.

BACKGROUND: Currently, there is no reliable blood-based marker to track tumor recurrence in endometrial cancer (EC) patients. Liquid biopsies, specifically, circulating tumor DNA (ctDNA) analysis emerged as a way to monitor tumor metastasis. The objective of this study was to examine the feasibility of ctDNA in recurrence surveillance and prognostic evaluation of high-risk EC. METHODS: Tumor tissues from nine high-risk EC patients were collected during primary surgery and tumor DNA was subjected to next generation sequencing to obtain the initial mutation spectrum using a 78 cancer-associated gene panel. Baseline and serial post-operative plasma samples were collected and droplet digital PCR (ddPCR) assays for patient-specific mutations were developed to track the mutations in the ctDNA in serial plasma samples. Log-rank test was used to assess the association between detection of ctDNA before or after surgery and disease-free survival. RESULTS: Somatic mutations were identified in all of the cases. The most frequent mutated genes were PTEN, FAT4, ARID1A, TP53, ZFHX3, ATM, and FBXW7. For each patient, personalized ddPCR assays were designed for one-to-three high-frequent mutations. DdPCR analysis and tumor panel sequencing had a high level of agreement in the assessment of the mutant allele fractions in baseline tumor tissue DNA. CtDNA was detected in 67% (6 of 9) of baseline plasma samples, which was not predictive of disease-free survival (DFS). CtDNA was detected in serial post-operative plasma samples (ctDNA tracking) of 44% (4 of 9) of the patients, which predicted tumor relapse. The DFS was a median of 9 months (ctDNA detected) versus median DFS undefined (ctDNA not detected), with a hazard ratio of 17.43 (95% CI, 1.616-188.3). The sensitivity of post-operative ctDNA detection in estimating tumor relapse was 100% and specificity was 83.3%, which was superior to CA125 or HE4. CONCLUSIONS: Personalized ctDNA detection was effective and stable for high-risk EC. CtDNA tracking in post-operative plasma is valuable for predicting tumor recurrence.