BaxΔ2 sensitizes colorectal cancer cells to proteasome inhibitor-induced cell death

Biochem Biophys Res Commun. 2018 Jan 29;496(1):18-24. doi: 10.1016/j.bbrc.2017.12.156. Epub 2017 Dec 29.


Proteasome inhibitors, such as bortezomib and carfilzomib, are FDA approved for the treatment of hemopoietic cancers, but recent studies have shown their great potential for treatment of solid tumors. BaxΔ2, a unique proapoptotic Bax isoform, promotes non-mitochondrial cell death and sensitizes cancer cells to chemotherapy. However, endogenous BaxΔ2 proteins are unstable and susceptible to proteasomal degradation. Here, we screened a panel of proteasome inhibitors in colorectal cancer cells with different Bax statuses. We found that all proteasome inhibitors tested were able to block BaxΔ2 degradation without affecting the level of Baxα or Bcl-2 proteins. Among the inhibitors tested, only bortezomib and carfilzomib were able to induce differential cell death corresponding to the distinct Bax statuses. BaxΔ2-positive cells had a significantly higher level of cell death at low nanomolar concentrations than Baxα-positive or Bax-negative cells. Furthermore, bortezomib-induced cell death in BaxΔ2-positive cells was predominantly dependent on the caspase 8/3 pathway, consistent with our previous studies. These results imply that BaxΔ2 can selectively sensitize cancer cells to proteasome inhibitors, enhancing their potential to treat colon cancer and other solid tumors.

Keywords: BaxΔ2; Bortezomib; Cancer therapy; Carfilzomib; Cell death; Proteasome inhibitors.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Apoptosis / drug effects*
  • Colorectal Neoplasms / drug therapy*
  • Colorectal Neoplasms / metabolism*
  • Colorectal Neoplasms / pathology
  • Dose-Response Relationship, Drug
  • HCT116 Cells
  • Humans
  • Proteasome Inhibitors / administration & dosage*
  • Treatment Outcome
  • bcl-2-Associated X Protein / metabolism*


  • Proteasome Inhibitors
  • bcl-2-Associated X Protein