A study by Britschgi et al. showed that STAT5 is activated by Janus kinase 2 (JAK2) that evoked a positive feedback loop to dampen the efficacy of PI3K/mTOR inhibition via secretion of interleukin-8 (IL-8) in several cell lines and primary breast tumors. The gene discussed is CXCL8; the disease is breast neoplasm.