VCOM Louisiana Research Day Program

Pharmacology

Md. Saqline Mostaq, MS; Amanda Raphael; Celine Asbury, OMS; Anish Gupta, OMS; Lin Kang, PhD; Yong-Yu Liu, PhD University of Louisiana Monroe, Monroe, Louisiana; Edward Via College of Osteopathic Medicine, Monroe, Louisiana 50 OVERCOMING DRUG RESISTANCE IN COLORECTAL CANCER CELLS WITH P53 MISSENSE MUTATION BY DOWNREGULATING GLUCOSYLCERAMIDE SYNTHASE EXPRESSION

The protein p53 encoded from TP53 tumor suppressor gene is critical in preventing tumorigenesis and tumor progression. However, missense mutations in p53 have been detected frequently over 50% of cancer cases and can promote drug resistance and metastasis by inducting cancer stem cells. Glucosylceramide synthase (GCS) is a rate-limiting enzyme in the synthesis of glycosphingolipids (GSLs) and overexpression of GCS responding to chemotherapy has been linked to drug resistance and tumor progression. Our hypothesis was that inhibiting GCS by knocking out the UGCG gene with CRISPR-Cas9 could reverse cancer drug resistance. Using cell and animal models, we found that UGCG knockout (KO) sensitized colon cancer cells to anticancer drugs. RT-qPCR confirmed that WiDr/UGCG KO cells and tumors expressed low levels of UGCG mRNA. The KO cells had approximately 2-fold lower IC 50 value for the chemotherapy drug oxaliplatin and 4-fold slower cell migration compared to parent WiDr cells. In animal study, WiDr/UGCG KO tumors showed significantly reduced volume compared to WiDr tumors treated with oxaliplatin. Treatment with the GCS inhibitor Genzyme-667161 sensitized WiDr cell and tumors to oxaliplatin. These findings suggest that Cer-glycosylation by GCS

plays a crucial role in promoting cancer drug resistance. To further validate our findings, we plan to conduct RNA sequencing, HPLC analysis, stem cell analysis, tumor sphere assay, immunohistochemistry, and Western blot analysis. These analyses will help identify key molecules regulating cancer stem cell genesis and underlying Cer-glycosylation regulating mutant protein expression and could lead to the development of new strategies for targeting Cer glycosylation in cancer treatment.

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