BTK and cancer: Notably, three of the inhibitors in this quadrant target the protein kinase C family (enzastaurin/LY317615 and LY333531), in addition to others, such as inhibitors targeting p38 MAPK (doramapimod), protein kinase A (H‐89), Bruton's tyrosine kinase (BTK) and the hedgehog pathway (cyclopamine), which have previously been found to play important roles in chemoresistance among broad cancers including colorectal, breast and prostate cancer [19, 20, 21, 22].