An alternative hypothesis, which is supported by the observation that studies on colorectal cancer without liver metastases have not reported altered T-cell numbers [153], is that liver metastasis might mediate immune function by the Fas/FasL axis, which prevents systemic anti-tumor immunity, and this effect should be recognized in anti-tumor therapies, especially for cancers with or without liver metastasis. This evidence concerns the gene FAS and colorectal cancer.