Survival of cancer cells relies mainly on their capacity to escape from immune surveillance. Activation of immune checkpoints is one way to escape from immune system, mediated through inhibition of T cell responses [1]. The advent of immune checkpoint inhibitors (ICIs) has marked a major shift in cancer treatment paradigm and has become a novel therapeutic approach for the management of cancer. ICIs are monoclonal antibodies (mAb) that facilitate T cell responses through blocking immune checkpoint mediators, the result of which is the amplification of natural anti-tumor function of immune system [2]. Programmed death-1 (PD-1), cytotoxic T Lymphocyte associated antigen-4 (CTLA-4) and programmed death-ligand 1 (PD-L1) are common inhibitory immune checkpoints that their blockade have shown clinical benefits for a number of solid tumors [1]. However, responses are not well pursued for majority of patients and are different in various solid tumor types [3]. Therefore, in order to optimize treatment schedules a search for application of appropriate factors to determine therapeutic efficacy in patients under ICI therapy could be a great help. PD-L1 is a known biomarker of response to immunotherapy [4], but whether it can be applied for response prediction in patients under combination therapy with the PD-1 inhibitor nivolumab and the CTLA-4 inhibitor ipilimumab is an open question in the area. Here, we aimed to give an answer to this question through assessing the impact of PD-L1 expression state in a number of advanced solid cancer patients under combo nivolumab-ipilimumab therapy.