AXL receptor tyrosine kinase was reported for inducing AR-negative PCa cells PC-3 and DU-145 in the MC3T3-E1 co-culture [25], but AR-positive C4-2B cells do not express AXL proteins although we observed an increase of AXL expression in the RNA-Seq. The unique gene signature of dormant PCa cells was possibly a result of response to different tumor microenvironments. The gene discussed is NTRK1; the disease is neoplasm.