Thrombospondin-1 counteracts the p97 inhibitor CB-5083 in colon carcinoma cells

Area of Science:

• Molecular Biology
• Cancer Therapeutics
• Cellular Stress Response

Background:

• p97 (valosin-containing protein) is crucial for protein homeostasis and a target for cancer therapy.
• CB-5083 is a potent p97 inhibitor inducing proteotoxic stress in cancer cells.
• Mechanisms of cellular sensitivity and resistance to p97 inhibition are not fully understood.

Purpose of the Study:

• To investigate the role of Thrombospondin-1 (THBS1) in mediating resistance to p97 inhibition by CB-5083.
• To explore the functional link between THBS1 and cancer cell survival under p97 inhibition.

Main Methods:

• Immunoblotting and immunofluorescence assays to quantify THBS1 levels.
• Cell viability assays to assess sensitivity to CB-5083.
• Flow cytometry to analyze cell cycle distribution (sub-G1 population).
• Caspase activity assays to measure apoptosis.

Main Results:

• CB-5083 treatment significantly upregulated THBS1 expression in HCT116 cells.
• Blocking THBS1 induction sensitized cells to CB-5083, enhancing growth inhibition.
• Suppression of THBS1 increased the sub-G1 population and caspase 3/7 activity, indicating enhanced apoptosis.

Conclusions:

• THBS1 plays a key role in conferring resistance to CB-5083, a p97 inhibitor.
• THBS1 functions to promote cancer cell survival in response to p97 inhibition.
• Targeting THBS1 may represent a strategy to improve the efficacy of p97 inhibitors in cancer treatment.