PTK2 and cancer: It has been suggested that there is a significant difference in the expression of FAK between non-tumourigenic and tumourigenic cells, with most studies indicating increased expression of FAK messenger ribonucleic acid (mRNA) in several cancer types, including invasive breast cancer, colon cancer, and prostate cancer, implicating that FAK may be involved in the progression of tumours [33,38,39,40].