Cathepsin B is involved in the apoptosis intrinsic pathway induced by Bacillus Calmette-Guérin in transitional cancer cell lines

Abstract

Bacillus Calmette-Guérin (BCG) is the most effective treatment for superficial and in situ transitional bladder cancer. Although the complete mechanisms for its effect are not fully understood yet, both immunological and direct effects on tumor cells have been proposed. It has been proposed that apoptotic tumor cells could be better inducers of immunity than necrotic ones. Thus, apoptosis of bladder cancer cells could contribute to a global response to BCG. Lysosomal hydrolase cathepsin B (CB) is involved in the apoptotic process and has a key role in breast cancer cell programmed death through the activation of a pro-apoptotic protein BID. Truncated BID participates in the mitochondrial apoptotic pathway that involves the activation of pro-caspase 9. The possibility that CB can be involved in apoptosis of TCC line has not been explored yet. Therefore, we analyzed the participation of CB in BCG-induced apoptosis of human and murine TCC lines. Apoptosis was evaluated by a morphologic assay and CB activity by a substrate-specific colorimetric method. Expression of CB, BID and pro-caspase 9 was determined by Western blotting. BCG induced apoptosis of murine (MBT2, MB49) and human (T24) TCC lines. An increase in both CB activity and protein was also observed. The apoptosis of T24 and MB49 cell lines was mediated by activation of pro-caspase 9 and BID, both proteins are involved in mitochondrial apoptosis. Apoptosis and activation of pro-caspase 9 and BID were inhibited by CA-074Me (CA), a cell permeable CB inhibitor. Thus, CB is involved in BCG-induced apoptosis of TCC lines, using at least in part the mitochondrial pathway.

Sorafenib induces cathepsin B-mediated apoptosis of bladder cancer cells by regulating the Akt/PTEN pathway. The Akt inhibitor, perifosine, enhances the sorafenib-induced cytotoxicity against bladder cancer cells.

“…CB has been found to activate the conversion of Bid to its active form tBid and consequently to trigger the intrinsic pathway of apoptosis [29]. Thus, the effect of sorafenib on Bid activation was evaluated.…”

“…Then, BID activation and release of the tBid fragment [19], mitochondrial depolarization and cytochrome c release, ROS production and caspase activation are induced, resulting in the complete execution of the intrinsic pathway of apoptosis [17,45]. Similarly, in murine (MBT2 and MB49) and human T24 BC cells, Bacillus Calmette-Guerin induces CB activation and Bid fragmentation, thereby activating the intrinsic apoptotic pathway [29]. The effect of sorafenib treatment on CB activation in BC cells was further supported by a molecular docking analysis of the molecular interaction between CB and sorafenib that indicated a complete insertion of sorafenib into the catalytic groove of CB with a strong binding affinity (25-fold higher than pazopanib).…”

Lysosomal membrane permeabilization in cell death

“…In addition, when full-length Bid was treated with cathepsins B, H, L and S, the resulting cleavage product was fully capable of releasing cytochrome c from isolated mitochondria (Cirman et al, 2004). CB-dependent Bid cleavage has been observed in various cell lines such as glioma cells killed by interleukin-24 (Yacoub et al, 2008), TTC bladder cancer cells killed by Bacillus Calmette-Gue´rin (Sandes et al, 2007), U2O2 osteosarcoma cells and oral squamous cell carcinoma with TRAIL (Garnett et al, 2007) (Nagaraj et al, 2006) and MCF-7 breast cancer cells exposed to camptothecin (Lamparska-Przybysz et al, 2006). Bid also represents a direct downstream target of CD.…”

“…Mycobacterium tuberculosis-infected macrophages undergo cathepsin-dependent caspase-independent cell death , and infection with Bacillus Calmette-Gue´rin also induces LMP and cell death (Sandes et al, 2007). A recent report indicates that virulent strains of M. tuberculosis and M. leprae (but not M. bovis and Bacillus Calmette-Gue´rin) translocate from lysosomes to the cytosol, which then can cause apoptotic cell death within a week (van der Wel et al, 2007).…”

Animal Models for Basic and Preclinical Research in Bladder Cancer

“…This immune therapy has been used without modification since 1976 (Morales et al, 1976). In addition to the direct anti-tumor effect (Sandes et al, 2007), it is widely recognized that intravesical BCG therapy is more potent in preventing tumor recurrence than any other intravesical chemotherapy (Sylvester, 2009). However, about 20% of patients either fail to respond initially or relapse within the first five years of treatment (Smaldone et al, 2009).…”