PO-039 Examination of the anti-tumour and neuropathic side effect responses of first generation and second generation proteasome inhibitors

Abstract

IntroductionThe overall goal in cancer treatment is to damage cancer cell macromolecules that causes the cancer cells to die. But in the treatment process, the defense mechanisms developed by the cancer cells affect the response to the treatment. As we have shown in our studies, cancer cells after anti-cancer stress have about 10–20 times more proteasome activation than healthy cells. Therefore, proteasome inhibition plays an important role in the prevention of resistance and recurrence in cancer treatment.Bortezomib, the first generation proteasome inhibitor, is used intensively, in hematologic cancer types, and significantly increases patient survival. However, it causes significant side effects such as neuropathy. New proteasome inhibitors are being produced to reduce side effects in the market. These inhibitors include clinical studies as well as preclinical studies. However, the lack of side-effect studies causes the early termination of clinical trials.Material and methodsIn this study, we compared the anti-tumour effects and neural toxicities of first generation and second-generation proteasome inhibitors in co-culture model. In this direction, human neural progenitor cells and K562 leukaemia cells were used. Co-cultures were incubated with 100 nM proteasome inhibitors for 24 hour and effects on the cancer cells and neural cells were analysed separately. Apoptotic cell death was evaluated with Annexin V/PI double staining by flow cytometry in K562 cells, and also PARP, Caspase 9 protein levels have been analysed in both cells. Protein oxidation related parameters such as protein carbonyls, ubiquitinated proteins, and HSP levels were investigated for understanding the stress response in both cells. Additionally, cytoskeleton proteins β-actin and β- tubulin changes were assessed in neural cells with confocal microscopy.Results and discussionsOur data showed that new proteasome inhibitors are less toxic in neural cells when compared to bortezomib. Protein carbonyls and ubiquitinated proteins were highest in bortezomib treated cells. On the other hand, especially carfilzomib has a lower anti-tumour activity in K562 cells when compared to bortezomib.ConclusionThis study may bring a highlight for the clinical usage and side effects of new proteasome inhibitors.