Moreover, we also found that Stat3 also contributed to the elevation of IL-6 in drug resistant cell lines (KB-CPT100 and MCF-7/ADR) and that Jak2/Stat3 pathway cooperated with other IL-6 downstream pathways to regulate the expression of IL-6 in various drug resistant cancer cell lines and in clinically isolated lung cancer cells. Here, STAT3 is linked to lung cancer.