Compound 4a induces paraptosis in hepatocellular carcinoma through
endoplasmic reticulum stress mediated by CRT protein
Abstract
Background and purpose Currently, the clinical benefits of liver cancer
treatment are still limited. Emerging evidences have highlighted that
paraptosis may be an effective strategy to threapy liver cancer. In our
previous studies, compound 4a was found to induce paraptosis in cancer
cells. Here, the characteristics of compound 4a induced paraptosis were
further revealed, and for the first time, the target and related
molecular mechanisms of compound 4a induced paraptosis in liver cancer
were explored. Study design and methods The effect and mechanism of
compound 4a on liver cancer cells both in vitro and in vivo. And the
targets of compound 4a that triggering paraptosis, were identified and
confirmed by using the technology of mass spectrometry-based drug
affinity responsive target stability(DARTS), siRNA, and Cellular thermal
Shift Assay(CETSA). Intracellular calcium concentration and protein
distribution were detected by Cal520-AM and immunofluorescence,
respectively. Results We found that compound 4a can effectively induce
paraptosis-like cell death in liver cancer both in vitro and in vivo,
and its effect is comparable to the first-line anti-liver cancer drugs
oxaliplatin while with higher safety. We identified that
Calreticulin(CRT) protein as a target of compound 4a, which causing
cellular endoplasmic reticulum(ER) stress and calcium overload. CRT
knockdown increased cell proliferation and reduced cytoplasmic vacuoles,
which was associated with inhibited ER stress and paraptosis.
Conclusions Our study provides a potential safe and effective agent for
the treatment of liver cancer. Moreover, we have clarified
characteristics of compound 4a-triggered paraptosis and revealed a
unique function of CRT in paraptosis.