The immune system tends to eliminate the host when it cannot control pathogenic threats: Evolutionary, medical, and epidemiologic perspectives.

We recently showed that a minimally-invasive removal of MDA-MB-231HM primary tumors (PTs) and elimination of their secreted factors (including IL-6, IL-8, VEGF, EGF, PDGF-aa, MIF, SerpinE1, and M−CSF), caused regression of spontaneous micro-metastases into a non-growing dormant state. To explore the underlying mechanisms and potential clinical ramifications of this phenomenon, we herein used the MDA-MB-231HM human breast cancer cell-line, in-vitro, and in vivo following orthotopic implantation in immune-deficient BALB/C nu/nu mice. Employing bioluminescence imaging, we found that adding laparotomy to minimally-invasive removal of the PT caused an outbreak of micro-metastases. However, perioperative β-adrenergic and COX-2 inhibition, using propranolol + etodolac, maintained metastatic dormancy following laparotomy. In-vitro, β-adrenergic agonists (epinephrine or metaproterenol) and prostaglandin-E2 markedly increased MDA-MB-231HM secretion of the pro-metastatic factors IL-6, IL-8, and VEGF, whereas cortisol reduced their secretion, effects that were maintained even 12 h after the washout of these agonists. In-vivo, laparotomy elevated IL-6 and IL-8 levels in both plasma and ex-vivo PT spontaneous secretion, whereas perioperative propranolol + etodolac administration blocked these effects. Similar trends were evident for EGF and MIF. Promoter-based bioinformatics analyses of excised PT transcriptomes implicated elevated NF-kB activity and reduced IRF1 activity in the gene regulatory effects of laparotomy, and these effects were inhibited by pre-surgical propranolol + etodolac. Taken together, our findings suggest a novel mechanism of post-operative metastatic outbreak, where surgery-induced adrenergic and prostanoid signaling increase the secretion of pro-metastatic factors, including IL-6, IL-8, and VEGF, from PT and possibly residual malignant tissue, and thereby prevent residual disease from entering dormancy.