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Jan 18, 2019

RPG Seminar Series (Speaker: Miss CUI Di / Miss FENG Zhen)

Date: Friday, 18 January 2019

Venue: Seminar Room 7, LG1/F
Laboratory Block, Faculty of Medicine Building
21 Sassoon Road, Hong Kong

Time: 5:00 p.m.

Title: Role and mechanism of miR-338-5p in regulating metastasis of esophageal cancer
Speaker: Miss CUI Di (PhD candidate)

Esophageal squamous cell carcinoma (ESCC) is a subtype of esophageal cancer of which the prognosis is dismal due to high rate of local invasion and distant metastasis. Increasing studies highlight the importance of microRNAs (miRNAs) as tumor suppressors. Previous study in our laboratory found that miR-338-5p was frequently downregulated in primary ESCC and could modulate chemoresistance in ESCC via targeting Id1. However, whether miR-338-5p has any inhibitory function on other targets in ESCC is still not fully understood. Therefore, this study focuses on find novel targets of miR-338-5p and further investigate its role and mechanism in regulating ESCC metastasis. We found that miR-338-5p has inhibitory effect on ESCC cell migration and invasion in vitro. Further study showed that miR-338-5p could interact with 3’-untranslated region (UTR) of epidermal growth factor receptor (EGFR) and inhibit its expression, indicating that EGFR may mediate the suppression of miR-338-5p on ESCC cell motility and metastasis.

Title: A mechanistic study of phosphatidylinositol-mediated receptor endocytosis at the podosome
Speaker: Ms FENG Zhen (PhD candidate)

Cells can form different types of adhesion structures with the extracellular matrix. Podosomes and invadopodia are integrin-mediated adhesions that are often found in cancer cells, monocyte-derived cells and oncogene-transformed fibroblasts. In particular, Src-transformed mouse embryonic fibroblasts (MEF) develop podosome arc and rosettes with spatial enrichment of various polyphosphoinositides (PIs). Roles of individual PI in the podosome are not fully known. In this study, we found that PI(3,4)P2 lipids are specifically enriched at the rear part of the podosome arc, as well as at the micrometer-long tubular membrane invagination (membrane tube) behind the podosome arc. PH-Tapp1 and PX-Tks5 are utilized as specific markers to monitor the spatiotemporal distribution of PI(3,4)P2 lipids. Local activation of phosphatidylinositol 3-kinases and phosphotases cause flunctuations of PH-Tapp1 level across podosome arc. Bar-domain protein FBP17, SNX9, dynamin2, and dynein-associated Ankyrin-B are recruited at difference phases during the elongation and fission of membrane tubes. Membrane receptor integrin-beta3, DDR1, and GPI-linked proteins are enriched in the membrane tube and internalized into endosomal network in a podosome-dependent and microtubule-dependent manner. Thus, biogenesis of PI(3,4)P2 lipids at the podosome can locally regulate receptor endocytosis and adhesion turnover at the podosome.