STAT3 and in situ carcinoma: However, in immunosuppressive microenvironment where immune surveillance is diminished due to chronic inflammation or oncolytic virus, the infiltration of immune cells will decrease, and the cytokine interleukin-6 (IL-6) will activate the JAK/STAT3 signaling pathway in monocytes (120), which ultimately contributes to abnormal cells escaping immune elimination and proliferating into carcinoma in situ (CIS).