Bowman-Birk protease inhibitor from soybeans enhances cisplatin-induced cytotoxicity in human mesothelioma cells

Abstract

Abstract. Malignant mesothelioma (MM) is an aggressive cancer with no effective treatment options. Enforced expression of the gap junction (GJ) component connexin 43 (Cx43) increases the sensitivity of MM cells to cisplatin. BowmanBirk protease inhibitor (BBI) induces the restoration of Cx43 in several types of tumor cells. In this study, we examined the capability of BBI to enhance the cytotoxic effect of cisplatin in MM cells via the induction of Cx43. Human MM H28 cells were used. Cell viability was evaluated by a WST-1 assay and proteasomal activity was determined by fluorometric analysis. Protein and mRNA levels were determined by immunoblot analysis and real-time RT-PCR, respectively. GJ function mediated by Cx43 was evaluated using the scrapeloading method. BBI effectively inhibited H28 cell growth in a dose-dependent manner (200-400 µg/ml). In parallel with the growth inhibition, Cx43 levels (mRNA and protein) and GJ function were elevated by BBI treatment. Knockdown of BBI-induced Cx43 by an antisense nucleotide treatment almost cancelled the growth inhibition. BBI enhanced cisplatin-induced cytotoxicity in H28 cells, and down-regulation of Cx43 by the antisense nucleotide treatment abrogated the enhancing effect of BBI. The induction of Cx43 by BBI contributed to Src inactivation and subsequent induction of Bax. Furthermore, an Src inhibitor (SU6656) also enhanced cisplatin-induced cytotoxicity in H28 cells. These results suggest that BBI improves the cytotoxic efficacy of cisplatin in H28 cells via the inhibition of Src signaling.

Targeting SRC Family Kinases in Mesothelioma: Time to Upgrade

“…Some studies performed in MM cell lines suggested that SFK inhibitors were able to increase the sensitivity to the chemotherapeutic agents currently used in MM therapy. In particular, the SFK inhibitor SU6656 enhanced cisplatin cytotoxicity in MM cells [47,48]. Moreover, dasatinib increased cisplatin-induced apoptosis of MM cells grown as multicellular spheroids, which mimic MM cell aggregates found in pleural effusions and are more resistant to cisplatin treatment [52].…”

“…Preclinical studies [43,47,48] SI83 * and SI91 * pyrazolo [3,4-d]pyrimidines derivatives BCR-ABL, SFKs Preclinical studies [44,49] The table reports the main SFK inhibitors used in clinical trials for different cancer types. In addition, SFK inhibitors used in preclinical studies in malignant mesothelioma (MM) cells are also included.…”

“…In preclinical studies, SFK inhibitors proved antitumor activity in MM cells, both alone [32,49] and in combination with either the chemotherapeutic agents currently used for MM treatment [47,48,52,53] or other tyrosine kinases inhibitors [31]. However, despite these encouraging preclinical observations, SFK inhibition was not successful in early clinical trials in MM patients [50,51].…”

“…CX43 is a direct substrate of SRC [109], which phosphorylates its C-terminal tail, resulting in inhibition of GJIC; moreover, there is a reciprocal regulation between CX43 and SRC, with CX43 inhibiting, in turn, SRC activity [110] (Figure 2). The role of the SRC-CX43 relationship in MM progression has not yet been thoroughly investigated, although a couple of studies found that experimentally increased levels of CX43 resulted in decreased SRC expression, reduced growth rate, and sensitization to cisplatin [47,48].…”

Inhibitors of Serine Proteinase - Application in Agriculture and Medicine

“…Similar results were obtained in cell culture H28 of malignant mesothelioma. When adding Bowman-Birk protease inhibitor from soybeans at concentrations of 200-400 μg/ml Inhibition of cell growth (Kashiwagi et al, 2011). Currently, research is continuing to explore mechanisms of toxicity.…”