Since the growth inhibition of MDA-MB-231 ΔpBK-ITIH5 clones known to re-express the full-length ITIH5 protein could not be further triggered, the responsiveness of cancer cells according to the ITIH5 polypeptides applied may depend on the availability of cell-type-specific factors to restore ITIH5’s tumor suppressive pathway. The gene discussed is ITIH5; the disease is cancer.