Assessment of proteasome concentration and chymotrypsin-like activity in plasma of patients with newly diagnosed multiple myeloma

• Proteasome concentration and its activity reflect the tumour burden in MM patients since patients in stage III had significantly higher levels compared to those in stage I.
• The elevated proteasome concentrations found in advanced MM stages may be related to the growth of myeloma cells since the proteasome level correlate with IL-6 and β2M.
• Higher proteasome ChT-L activity, unlike the concentration, was proved to be an indicator of a shorter progression free survival.

The ubiquitin-proteasome pathway is implicated in the pathogenesis of many haematologic malignancies, including multiple myeloma. Under conditions of rapid cell turnover and growth rate, proteasomes are returned into circulation. The measurement of their levels or activity could offer a new approach to diagnosis, prognosis and monitoring of anticancer treatment in carcinoma patients.We analysed proteasome concentration and chymotrypsin-like (ChT-L) activity in the plasma of 64 patients with a newly diagnosed multiple myeloma and 30 healthy volunteers. The values were found to be significantly higher in the studied patients and advanced disease stages compared to the control group, and decreased significant after chemotherapy. Both proteasome concentration and ChT-L activity correlated with adverse prognostic factors, such as lactate dehydrogenase and β2-macroglobulin. We also showed that proteasome concentration positively correlates with IL-6 level, as opposed to proteasome ChT-L activity. Of note, higher proteasome ChT-L activity, unlike the concentration, was proved to be an indicator of a shorter progression free survival, constituting thereby an important prognostic marker.