PTEN and urinary bladder cancer: In vitro, bladder cancer cell lines can internalize BCG via macropinocytosis, a non-specific mechanism for the uptake of large particles that depends on the activation of the serine/threonine kinase P21 activated kinase (Pak1) by certain tumor aberrations, including activating mutations of Ras and inactivating mutations of phosphatase and tensin homolog (PTEN) [19,20].