RAB27A is an independent prognostic factor in clear cell renal cell carcinoma

Exosome-mediated secretion of miR-127-3p regulated by RAB27A accelerates metastasis in renal cell carcinoma

BACKGROUND

The exosome-mediated extracellular secretion of miRNAs occurs in many cancers, and RAB27A is a potent regulator of exosome secretion. For metastatic renal cell carcinoma (RCC), this study examines the mechanisms of cancer metastasis via the RAB27A-regulated secretion of specific miRNAs.

METHODS

RAB27A knockdown (KD) and overexpressing (OE) RCC cells were used to examine cell migration and adhesion. The particle counts and sizes of exosomes in RAB27A OE cells were analyzed using Exoview, and those of intraluminal vesicles (ILV) and multivesicular bodies (MVB) were measured using an electron microscope. Analysis of RNA sequences, protein-protein interaction networks, and the competing endogenous RNA (ceRNA) network were used to identify representative downregulated miRNAs that are likely to undergo cargo-sorting into exosomes and subsequent secretion. A molecular beacon of miR-137-3p, one of the most representatively downregulated genes with a fold change of 339, was produced, and its secretion was analyzed using Exoview. RAB27A OE and control cells were incubated in an exosome-containing media to determine the uptake of tumor suppressor miRNAs that affect cancer cell metastasis.

RESULTS

Migration and cell adhesion were higher in RAB27A OE cells than in RAB27A KD cells. Electron microscopy revealed that the numbers of multivesicular bodies and intraluminal vesicles per cell were higher in RAB27A OE cells than in control cells, suggesting their secretion. The finding revealed that miR-127-3p was sorted into exosomes and disposed of extracellularly. Protein-protein interaction analysis revealed MYCN to be the most significant hub for RAB27A-OE RCC cells. ceRNA network analysis revealed that MAPK4 interacted strongly with miR-127-3p.

CONCLUSION

The disposal of miR-127-3p through exosome secretion in RAB27A overexpressing cells may not inhibit the MAPK pathway to gain metastatic potential by activating MYCN. The exosomes containing miRNAs are valuable therapeutic targets for cancer treatment.

Circulating tumor cells reveal early predictors of disease progression in patients with stage III NSCLC undergoing chemoradiation and immunotherapy

Circulating tumor cells (CTCs) are early signs of metastasis and can be used to monitor disease progression well before radiological detection by imaging. Using an ultrasensitive graphene oxide microfluidic chip nanotechnology built with graphene oxide sheets, we were able to demonstrate that CTCs can be specifically isolated and molecularly characterized to predict future progression in patients with stage III non-small cell lung cancer (NSCLC). We analyzed CTCs from 26 patients at six time points throughout the treatment course of chemoradiation followed by immune checkpoint inhibitor immunotherapy. We observed that CTCs decreased significantly during treatment, where a larger decrease in CTCs predicted a significantly longer progression-free survival time. Durvalumab-treated patients who have future progression were observed to have sustained higher programmed death ligand 1+ CTCs compared to stable patients. Gene expression profiling revealed phenotypically aggressive CTCs during chemoradiation. By using emerging innovative bioengineering approaches, we successfully show that CTCs are potential biomarkers to monitor and predict patient outcomes in patients with stage III NSCLC.

Lack of Rab27a attenuates foam cell formation and macrophage inflammation in uremic apolipoprotein E knockout mice

As the most common cardiovascular disease, atherosclerosis (AS), is a leading cause of high mortality in patients with chronic renal failure. Rab27a has been reported to regulate the progression of cardiovascular and renal diseases. Nevertheless, little studies investigated the role and mechanism of Rab27a in uremic-accelerated AS (UAAS). An animal model of UAAS was established in apolipoprotein E knockout (apoE^-/-) mice using 5/6 nephrectomy (NX). We conducted in vitro and in vivo functional experiments to explore the role of Rab27a in UAAS, including the presence of oxidized low-density lipoprotein (ox-LDL). Rab27a expression was upregulated in the plaque tissues of NX apoE^-/- mice. The knockout of Rab27a (Rab27a^-/-) reduced AS-induced artery injury, as manifested by the reductions of plaque area, collagen deposition, inflammation and lipid droplet. Besides, cholesterol efflux was increased, while the expression of lipid metabolism-related proteins and the secretions of pro-inflammatory factors were decreased in ox-LDL-induced NX Rab27a^-/- apoE^-/- mice group. Further, Rab27a deletion inhibited the activation of nuclear factor κB (NF-κB) pathway. In conclusion, our study indicated that Rab27a deficiency attenuated foam cell formation and macrophage inflammation, depending on the NF-κB pathway activation, to inhibit AS progression in uremic apoE^-/- mice. This finding may provide a new targeting strategy for UAAS therapy.

RAB27B expression in pancreatic cancer is predictive of poor survival but good response to chemotherapy

BACKGROUND

Pancreatic cancer is the 4th leading cause of cancer-related death with poor survival even after curative resection. RAB27A and RAB27B are key players in the exosome pathway where they play important roles in exosome secretion. Evidence suggests that RAB27A and RAB27B expression not only leads to tumor proliferation and invasion, but also plays an important role in antigen transfer necessary for anticancer immunity.

OBJECTIVE

In this study, we analyze the expression of RAB27A and RAB27B in patients after pancreatic cancer surgery with or without adjuvant chemotherapy and its influence on overall survival.

METHODS

We analyzed a total of 167 patients with pancreatic cancer for their RAB27A and RAB27B expression. We dichotomized the patients along the median and compared survival in patients with high and low RAB27A and RAB27B expression with or without adjuvant chemotherapy treatment.

RESULTS

We found a significant improvement in overall survival in patients with a negative resection margin (p= 0.037) and in patients who received adjuvant chemotherapy (p= 0.039). The survival benefit after chemotherapy was dependent on RAB27B expression status: only the subgroup of patients with high RAB27B expression benefited from adjuvant chemotherapy (p= 0.006), but not the subgroup with low RAB27B expression (p= 0.59). Patients with high RAB27B expression who did not receive adjuvant chemotherapy showed a trend towards worse survival compared to the other subgroups. This difference was abolished after treatment with adjuvant chemotherapy.

CONCLUSION

These results suggest that RAB27B expression in pancreatic cancer might identify a subgroup of patients with poor survival who might respond well to adjuvant chemotherapy. If resectable, these patients could be considered for neoadjuvant chemotherapy to minimize the risk of not receiving adjuvant chemotherapy. Further prospective studies are needed to confirm these findings.

RAB27A promotes the proliferation and invasion of colorectal cancer cells

Colorectal cancer (CRC) is one of the most commonly diagnosed cancer types worldwide. Despite significant advances in prevention and diagnosis, CRC is still one of the leading causes of cancer-related mortality globally. RAB27A, the member of RAB27 family of small GTPases, is the critical protein for intracellular secretion and has been reported to promote tumor progression. However, it is controversial for the role of RAB27A in CRC progression, so we explored the exact function of RAB27A in CRC development in this study. Based on the stable colon cancer cell lines of RAB27A knockdown and ectopic expression, we found that RAB27A knockdown inhibited proliferation and clone formation of SW480 colon cancer cells, whereas ectopic expression of RAB27A in RKO colon cancer cells facilitated cell proliferation and clone formation, indicating that RAB27A is critical for colon cancer cell growth. In addition, our data demonstrated that the migration and invasion of colon cancer cells were suppressed by RAB27A knockdown, but promoted by RAB27A ectopic expression. Therefore, RAB27A is identified as an onco-protein in mediating CRC development, which may be a valuable prognostic indicator and potential therapeutic target for CRC.

Prognostic significance of Rab27 expression in solid cancer: a systematic review and meta-analysis

Rab27 is an essential molecule of vesicle fusion and trafficking in exosome secretion process, which plays important roles in cancer progression and metastasis. Recent studies reported that Rab27 expression is also associated with cancer prognosis. Therefore, we performed a meta-analysis to reveal the prognostic significance of Rab27 expression in solid cancer. Data were extracted by searching on PubMed, Embase and Cochrane library until February 15 2020. Pooled hazard ratio (HR) with confidence interval (CI) was calculated to evaluate the association between Rab27 expression and survival in solid cancer. Ten studies with 1434 cancer patients were including for this meta-analysis. High expression of Rab27 was associated with poor survival (HR 2.67, 95% CI 1.52-4.69, p = 0.001). High expression of Rab27A was significantly associated with lymph node metastasis (HR 1.53, 95% CI 1.00-2.34, p = 0.048). High expression of Rab27B was significantly correlated with lymph node and distant metastasis (HR 2.15, 95% CI 1.56-2.95, p < 0.001; HR 6.80, 95% CI 3.12-14.85, p < 0.001), and higher TNM stage (HR 2.55, 95% CI 1.78-3.65, p < 0.001). This meta-analysis revealed that Rab27 expression could be a potential prognostic marker in solid cancer.

Prognostic Significance of Rab27A and Rab27B Expression in Esophageal Squamous Cell Cancer

Purpose

Rab27A and Rab27B, members of the Rab family of small GTPases, have aberrant expression and exert different roles in various cancers. However, their expression and potential prognostic values in esophageal squamous cell cancer (ESCC) still remain elusive. In the present study, we explored the association of Rab27A and Rab27B expression with clinical significance and prognosis in ESCC.

Patients and Methods

A total of 100 surgically resected ESCC tissues were examined to evaluate Rab27A and Rab27B expression levels using the immunohistochemistry method. The relationship of Rab27A and Rab27B with clinicopathological features and prognosis was analyzed. We also investigated the correlation between Rab27A and Rab27B through external and internal validation.

Results

High-expression Rab27A was found to be significantly correlated with N (p=0.045) and TNM (p=0.005) stage, while up-regulated Rab27B was remarkably associated with N stage (p=0.033), TNM stage (p=0.009), and differentiation (p=0.013). High expression of both Rab27A and Rab27B had a worse overall survival (OS) rate. In addition, multivariate Cox regression analyses were utilized to validate that Rab27B expression is an independent prognostic factor for unfavorable OS. Further combined analyses showed that the Rab27A^low/B^low group had a superior OS rate than the Rab27A^high/B^low group, Rab27A^low/B^high group, and Rab27A^high/B^high group. Nevertheless, the latter three groups displayed rare significance between each two comparisons. Furthermore, our data demonstrated that Rab27A expression was positively correlated with Rab27B expression, which were also verified in TCGA datasets.

Conclusion

Rab27A and Rab27B expression levels could be potentially novel prognostic biomarkers in ESCC.

Prognostic role of extracellular vesicles in squamous cell carcinoma of the lung

Background

Research on diagnosing recurrent non‐small cell lung cancer (NSCLC) and applying target gene treatment using exosomes in a less invasive way is very important. Recently, however, it has been argued that exosomes do not contain double‐stranded DNA (dsDNA) or histones. In this study, we describe the expression of extracellular vesicle (EV) markers in specimens from squamous cell carcinoma (SCC) of the lung and analyze their relationship with the prognosis of patients.

Methods

Clinical and pathological data were obtained from 96 patients who had undergone surgery for SCC of the lung. Tissue microarray blocks were made using representative paraffin blocks of samples from patients with SCC of the lung. Two pathologists graded the intensity of CD63, CD9, LC3A/B, P62, and ANXA1 expression as high or low expression. In addition, the authors designated the combined expression of these five independent markers as “positive EV expression” in this article.

Results

SCCs with low CD63 and SCCs with low EV expression showed unfavorable disease‐free survival (DFS) (P‐value = 0.037 and 0.006, respectively) in the survival analysis. The Kaplan‐Meier survival curve confirmed that the low EV expression showed a statistically significant relationship with unfavorable DFS (P‐value = 0.004). There were no statistically significant differences in DFS and disease‐specific survival in each low and high expression group for CD9, LC3A/B, ANXA1, and P62 in the Cox regression analysis.

Conclusions

As EV expression was related to the prognosis of lung SCC patients, a broader approach using different extracellular vesicles rather than a conventional exosome‐dependent one is needed.