Summary-Paper 54

Summary- paper 54: TFasting-induced RNF152 resensitizes gallbladder cancer cells to gemcitabine by inhibiting mTORC1-mediated glycolysis

Ying Tao,Zijun Gong,Sheng Shen,Yaqi Ding,Rui Zan,Bohao Zheng,Wentao Sun,Chaolin Ma, Mengxuan Shu,Xiao Lu, Han Liu,Xiaoling Ni,Houbao Liu,and Tao Suo

Questions/gaps addressed:

Gallbladder cancer has poor prognosis, often detected after metastasis. Fasting leads to reduced proliferation of cancer cells presumably by inhibiting AKT/mTOR signaling to prevent the Warburg shift and enhance cancer cell sensitivity to chemotherapy.
RNF152 was found in a genome-wide CRISPR-Cas9screen to identify genes involved in gemcitabine resistance in Gallbladder cancer. RNF152 is downregulated in several biliary tract cancers. What is the relationship between RNF152, mTORC1, p18/LAMTOR1, and gemcitabine resistance?

Major hypotheses:

Fasting upregulates the expression of RNF152 which targets p18/LAMTOR1 to inhibit the activity of mTORC1, reducing the activity of p-4E-BP1 and pS6K1, and thereby increase the sensitivity of gallbladder cancer cells to gemcitabine.

Key methods:

Human Gallbladder cancer cell lines (GBC-SD and SGC-996).
Short-term starvation (STS): fasting mimic medium (glucose-free DMEM supplemented with 0.5 g/L glucose and 1% FBS) for 48 h. Normal control media: DMEM with 10% fetal bovine serum.

Major takeaways:

When RNF152 is inhibited, levels of p18/LAMTOR1 increase. Addition of proteasome inhibitor, MG132 (10 mM), but not lysosome inhibitor, bafilomycin A1 (BafA, 100 nM, a V-ATPase inhibitor), stabilized p18, suggesting p18 is degraded by the proteasome. Lower levels of p18 also correlate with, lower mTORC1 activity, lower glycolysis, and reduced cell growth.