Oncogenic Activation of Pak1-Dependent Pathway of Macropinocytosis Determines BCG Entry into Bladder Cancer Cells

Abstract

Bacille Calmette-Guerin (BCG) is an attenuated strain of Mycobacterium bovis that is used widely as a vaccine for tuberculosis and is used as an effective treatment for superficial bladder carcinoma. Despite being the most successful cancer biotherapy, its mechanism of action and response determinants remain obscure. Here we establish a model system to analyze BCG interaction with bladder cancer cells, using it to show that these cells vary dramatically in their susceptibility to BCG infection. Unexpectedly, the uptake of BCG by bladder cancer cells occurs by macropinocytosis rather than phagocytosis. BCG entry into bladder cancer cells relied upon Rac1, Cdc42 and their effector kinase Pak1. The difference in susceptibility between BCG-permissive and BCG-resistant bladder cancer cells was due to oncogenic activation of signaling pathways that activate macropinocytosis, with PI3K activation stimulating BCG uptake independently of Akt. Similarly, activated Ras strongly activated Pak1-dependent uptake of BCG. These results reveal that oncogenic activation of macropinocytosis determines BCG uptake by bladder cancer cells, implying that tumor responsiveness to BCG may be governed by the specific mutations present in the treated cancer cell.

Selective inhibition of liver cancer growth realized by the intrinsic toxicity of a quantum dot–lipid complex

“…[38][39][40] Moreover, macropinocytosis serves as a key internalization pathway for intracellular delivery of various physiological, pathological, and therapeutic cargoes. 41 Reyes-Reyes et al showed that macropinocytosis was much more active in DU145 cancer cells than in the nonmalignant Hs27 cells and that amiloride pretreatment caused a reduction in FL-AS1411 uptake in DU145 cancer cells but only a slight increase in the nonmalignant Hs27 cells, 42 which is consistent with our results. Therefore, we suggest that macropinocytosis may be partially responsible for the difference in endocytosis capabilities in both cancer and normal cells, which subsequently results in the selective toxicity seen in the tumor cells.…”

Molecular Pathways: Targeting RAC–p21-Activated Serine–Threonine Kinase Signaling in RAS-Driven Cancers

“…PAK1 was found to be necessary and sufficient for growth factor- and Rac-induced macropinocytosis in NIH3T3 fibroblasts (60). Rac and PAK1 were found to be both necessary for Bladder cancer cell macropinocytotic uptake of Bacille Calmette-Guerin, a strain of bacteria used in the treatment of bladder carcinoma (61). Additionally, bacterial uptake was also stimulated by activated K-Ras or H-Ras and this activity was blocked by pharmacologic inhibition of group I PAKs (IPA-3).…”

Mechanism responsible for the antitumor effect of BCG-CWS using the LEEL method in a mouse bladder cancer model

“…In addition, BCG and CWS-NP were taken up by bladder cancer cells via a similar pathway. It was recently reported that BCG is taken up by bladder cancer cells via macropinocytosis [30]. In the case of CWS-NP, macropinocytosis is involved in its uptake by bladder cancer cells [9].…”