We examined expression of IL-1A, IL-1B, IL-6 and IL-8 in two pairs of gefitinib-sensitive (PC9, and HCC827) and gefitinib-resistant (PC9/gef, and HCC827/gef) lung cancer cell lines to identify the specific cytokine involved in gefitinib resistance by RT-qPCR. Here, IL1A is linked to lung cancer.