Molecular mechanisms of STARD3 addiction in HER2 tumors

Abstract

Human Epidermal growth factor Receptor 2 (HER2) is overexpressed and amplified in approximately 15–20% of breast cancers. HER2 is a tyrosine kinase receptor belonging to the EGFR family. HER2 amplification and overexpression play a central role in initiation, progression and metastasis of common cancers like lung, breast and gastric cancer (Hynes and MacDonald, 2009). HER2 amplification is a marker of poor prognosis, especially in breast and gastric cancer (Slamon and Clark, 1988). Although anti‐HER2‐targeted therapies have shown significant clinical benefits, de novo and acquired resistance remain a considerable issue (Garrett and Arteaga, 2011). Genomic profiling has demonstrated that HER2 positive‐tumors have additional alterations, and more importantly they co‐amplify and co‐express several genes on the 17q12 locus (Bièche et al., 1996; Kauraniemi et al., 2001; Tomasetto et al., 1995). Among these genes co‐expressed with HER2, our team identified and characterized STARD3, a gene belonging to the HER2 amplicon (Alpy and Tomasetto, 2014).STARD3 is a lipid transfer protein belonging to the START domain protein family (Alpy et al., 2001). This protein has two domains: the MENTAL domain anchors the protein in late endosomes and the cytoplasmic START domain allows cholesterol transport. Moreover, an FFAT motif present at the interface between the two domains of STARD3 interacts with VAP or MOSPD2 proteins localized in the endoplasmic reticulum (ER) (Alpy et al., 2013; Mattia et al., 2018). Thus, this interaction creates a membrane contact site between late endosomes and the ER allowing then the transfer of cholesterol towards late endosomes (Alpy et al., 2013; Wilhelm et al., 2017). Also, STARD3 has been functionally implicated in the survival of HER2‐amplified cells. Indeed, inhibition of STARD3 expression by RNA interference limits cell growth only in HER2‐amplified cells (Alpy and Tomasetto, 2014; Sahlberg et al., 2013). Thus, STARD3 belongs to the HER2 smallest region of amplification and its expression suggests that it contributes to HER2 tumor growth. We think that STARD3 cooperates with HER2 for tumor growth through an indirect molecular mechanism. Our results suggest that STARD3 acts on cancer cells by altering the normal cholesterol distribution and modifying the lipid composition of cellular membranes.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.