Cytokine expression active a variety of signaling pathways involved in drug resistance, either by autocrine regulation (cytokines secreted by tumor cells) or by paracrine regulation (cytokines secreted by stromal cells or tumor-associated cells; e.g. fibroblasts), resulting in a differential expression in drug resistant and sensitive cell lines (e.g. overexpression of interleukin-6 (IL6) and interleukin-8 (IL8) in resistant cell lines) [68]. Here, CXCL8 is linked to neoplasm.