Kent-Man Chu

Purpose: Gastric cancer is a leading cause of cancer-related mortality worldwide, with metastasis being the primary cause of death. Exosomes secreted by tumor cells are key mediators of intercellular communication and can prepare distant sites for metastasis by altering the local microenvironment. We hypothesized that exosomes released by gastric cancer cells deliver cargo that regulates specific proteins in recipient gastric cancer cells, thereby enhancing tumor progression and metastatic potential. Methods: Human gastric cancer cell lines were treated with exosomes isolated from the conditioned medium of other gastric cancer cells. Differential proteomic analysis was performed to identify proteins significantly altered by exosome treatment. ITGA2 expression was validated in exosome-treated cells and in clinical gastric cancer tissues versus adjacent normal tissues using RT-qPCR and western blotting. The functional role of ITGA2 was assessed by siRNA-mediated knockdown, followed by MTT proliferation assays and fluorometric transwell assays for migration and invasion. A second proteomic analysis was conducted on ITGA2-knockdown versus control cells to identify downstream targets and affected pathways. Results: Exosome treatment significantly upregulated ITGA2 expression in recipient gastric cancer cells. ITGA2 was also markedly overexpressed in human gastric cancer tissues compared with adjacent normal mucosa. Knockdown of ITGA2 significantly suppressed cell proliferation, migration, and invasion. Proteomic profiling of ITGA2-knockdown cells revealed numerous differentially expressed proteins enriched in pathways related to cell adhesion, motility, extracellular matrix organization, and intercellular signaling. Conclusion: Exosomes derived from gastric cancer cells induce ITGA2 overexpression in recipient tumor cells, where ITGA2 functions as an oncogene that promotes proliferation, migration, and invasion. The downstream targets of ITGA2 implicate multiple pro-tumorigenic signaling networks, suggesting that the exosomes–ITGA2 axis may represent a novel therapeutic target in gastric cancer progression and metastasis.

Introduction: MiRNAs play important roles in development of various cancers including gastric cancer. Exosomes are extracellular vesicles for translocating molecules. This study aimed to investigate the tumor suppressive roles of miR-379-5p in gastric cancer and to investigate the roles of exosomes in transporting miR-379-5p from intracellular to extracellular. Methods: Fifty-three pairs of gastric cancer and non-tumor tissue samples were collected. Five cell lines were applied. Functional assays including cell proliferation, cell migration and invasion, and cell adhesion assay were performed. Targets of miR-379-5p were screened and validated by Western blot. Expressions of endogenous miR-379-5p in gastric cancer cells and exosomal miR-379-5p in cell culture medium were evaluated by RT-qPCR. Medium of culturing AGS or BCG23 was applied for culturing MKN45 and HEK293T. Results: The results indicated that miR-379-5p was significantly downregulated in gastric cancer tissue samples and cell lines. Enforced expression of miR-379-5p inhibited gastric cancer cell proliferation, migration, and invasion, while miR-379-5p mimic enhanced cell adhesion to extracellular matrix. IGF1R was a potential target of miR-379-5p in gastric cancer. Expression of miR-379-5p was dramatically higher in exosomes in cell culture medium than its endogenous expression. Exosomes from cell culture medium of AGS or BCG23 could regulate endogenous expression of miR-379-5p in HEK293T cells. Conclusions: MiR-379-5p was significantly downregulated and it functioned as a tumor suppressor in gastric cancer. MiR-379-5p was highly expressed in exosomes of culture medium than its endogenous expression. MiR-379-5p could be translocated from cells into cell culture medium and entered certain cell types via exosomes.

MicroRNAs play significant roles in cancer initiation and progression. Exosomes are important extracellular vesicles for transporting molecules to distant sites. This study aims to investigate the functional roles of miR-4103p in primary gastric cancer, as well as the roles of exosomes in regulating expression of miR-410-3p. In this study, forty-seven pairs of human gastric cancer tissue samples were collected. Endogenous expression of miR-410-3p in tissue samples and cell lines, and expression of exosomal miR-410-3p in cell culture medium were evaluated by RT-qPCR. Functional assays including cell proliferation assay by MTT, cell migration and invasion assay by transwell, and cell adhesion assay were performed. Targets of miR-410-3p were screened. Cell culture medium of culturing cell lines established from stomach (AGS and BCG23) was applied for culturing cell lines established from other sites (MKN45 and HEK293T). It was found that miR-410-3p was significantly downregulated in gastric cancer. Overexpression of miR-410-3p inhibited gastric cancer cell proliferation, migration, and invasion. MiR-410-3p mimic enhanced cell adhesion. HMGB1 was a target of miR-410-3p in primary gastric cancer. Expression of exosomal miR410-3p in cell culture medium was dramatically higher than its endogenous expression. Exosomes from cell culture medium of AGS or BCG23 regulated endogenous expression of miR-410-3p in MKN45. In conclusion, miR-410-3p functioned as a tumor suppressor in primary gastric cancer. MiR-410-3p was higher expressed in exosomes of cell culture medium than its endogenous expression in cells. Endogenous expression of miR-410-3p in a distant site could be regulated by exosomes from the original site.

Aim: The global pandemic of COVID-19 has led to extensive practice of online learning. Our main objective is to compare different online synchronous interactive learning activities to evaluate students’ perceptions. Moreover, we also aim to identify factors influencing their perceptions in these classes. Methods: A cross-sectional, questionnaire-based study focusing on clinical year medical students’ perceptions and feedback was conducted between February 2021 –June 2021 at the University of Hong Kong. Online learning activities were divided into bedside teaching, practical skill session, problem-based learning (PBL) or tutorial, and lecture. A questionnaire based on the Dundee Ready Education Environment Measure (DREEM) was distributed to 716 clinical year students to document their perceptions. Results: One hundred responses were received with a response rate of 15.4% (110/716, including 96 from bedside teaching, 67 from practical skill session, 104 from PBL/tutorial, and 101 from lecture). For the mean score of the DREEM-extracted questionnaire, online PBL/tutorial scored the highest (2.72 ± 0.54), while bedside scored the lowest (2.38 ± 0.68, p = 0.001). Meanwhile, there was no significant difference when we compared different school years (p = 0.39), age (p = 0.37), gender (p = 1.00), year of internet experience (p = 0.59), or prior online class experience (p = 0.62). When asked about students’ preference for online vs face-to-face classes. Students showed higher preferences for online PBL/tutorial (2.06 ± 0.75) and lectures (2.27 ± 0.81). Distraction remains a significant problem across all four learning activities. A multivariate analysis was performed regarding students’ reported behavior in comparison with their perception through the DREEM-extracted questionnaire. The results showed that good audio and video quality had a significant and positive correlation with their perception of online bedside teaching, practical skill sessions, and PBL/tutorial. It also showed that the use of the video camera correlated with an increase in perception scores for lectures. Conclusion: The present analysis has demonstrated that students’ perception of different online synchronous interactive learning activities varies. Further investigations are required on minimizing distraction during online classes.

Gastric cancer is one of the leading causes of cancer death in the world. Early diagnosis and effective chemotherapy are vital to reduce the overall mortality. Prostaglandin E2 (PGE2) has been implicated as an important factor in gastric cancer carcinogenesis. ECF based regimen (epirubicin, cisplatin, 5-fluorouracil) is the first-line chemotherapy for advanced gastric cancer. However, patients develop resistance after chemotherapy. The aim of this study is sought to investigate the role of EP2 receptor, a PGE2 receptor, and the antagonism of EP2 receptor in response to ECF treatment. Expression of EP2 receptor was evaluated in gastric cancer tissue samples and cell lines. Cell proliferation and cell apoptosis assays were performed in vitro and in vivo, upon knockdown of EP2 recep-tor, antagonist of EP2 receptor and/or ECF treatment. Western Blot was applied for evaluation of proteins relating to cell cycle, apoptosis and drug transporter. Next generation sequencing and ingenuity pathway analysis were ap-plied for screening for downstream targets of EP2 receptor. Expressions of the targets of EP2 receptor were further evaluated in gastric cancer cells and tissues. In this study, we found that expression of EP2 receptor was significantly upregulated in gastric cancer. Inhibition of EP2 receptor reduced gastric cancer cell proliferation, induced cell cycle arrest proteins, and enhanced cell apoptosis. Moreover, knockdown of EP2 receptor by siRNA or antagonist sensitized gastric cancer cells to ECF. Silence of EP2 receptor also significantly abrogated gastric cancer growth in a mice model. Analysis revealed that CAV1 was a downstream target of EP2 receptor in gastric cancer. Our findings illustrated that blocking EP2 receptor reduced tumor growth and induced apoptosis in gastric cancer. This novel study unraveled CAV1 was a downstream target of EP2 receptor. Antagonizing EP2 receptor could be a potential therapeutic target in gastric cancer, in particular those with high EP2 receptor expression.

Background: Educational pedagogies were modified during the COVID-19 pandemic to minimise interruption to teaching. One approach has been the distance learning problem-based learning (PBL) tutorial utilising the online peer-to-peer platform. The aim of this study was to compare the performance of students using distance learning PBL tutorials using with that of students utilising the conventional face-to-face approach. Methods: This retrospective study was conducted in a single academic institution. We compared two groups of fourth-year medical students from the same class: one group used distance learning (DL); the other, the face-to-face (FF) method. We used students’ baseline performance at the preceding block for one-to-one propensity score matching. Students utilising the PBL tutorial were given grades by their tutors according to a standardised scoring system encompassing five key areas (score range: 0–10). The main outcome was a student’s total score (i.e., the sum of the scores from the five key areas, ranging from 0 to 50). Result: We matched 62 students in each group. With four tutorials, there were 490 observations, with 245 in each group. The mean total score for the DL group was 37.5 ± 4.6, which was significantly lower than that of the FF group (39.0 ± 4.4, p < 0.001). We noted that students in the DL group had a significantly lower scores for all five areas of proficiency: participation, communication, preparation, critical thinking and group skills. Conclusion: Findings of this study revealed that the performance of students utilising the DL PBL tutorials was lower than that of students participating in the conventional FF approach. Further studies are needed to ascertain the underlying cause.