PTPRJ and cancer: The present study investigated the effects of CD148 Q276P/R326Q polymorphisms in cancer cell proliferation, growth factor signaling (with emphasis on EGFR signaling), and the CD148 ligand‐induced cancer cell growth inhibition by stably expressing same level of WT or Q276P/R326Q forms of CD148 in A431D epidermoid carcinoma cells that lack CD148 expression.