Several mechanisms have been demonstrated to play a role in the development, survival, and promotion of metastases of various tumors. One of these key mechanisms is the inhibition of the immune system. In the current research study, we are investigating the effect of receptor agonists and antagonists on IDO RNA and protein expression in an LHRH receptor expressing human cervical cancer cell line (HeLa cells), it has been shown the IDO overexpression after treatment with LHRH analogs in different time intervals which helps the tumor to suppress the immune system.