Purpose: Preoperative or
neoadjuvant therapy (NT) is increasingly used in patients with locally advanced or
inflammatory breast cancer to allow optimal surgery and aim for pathologic response. However, many breast
cancers are resistant or relapse
after treatment. Here, we investigated conjunctive
chemotherapy-triggered events occurring systemically and locally, potentially promoting a
cancer stem-like cell (CSC) phenotype and contributing to
tumor relapse.Experimental Design: We started by comparing the effect of paired pre- and post-NT patient sera on the CSC properties of
breast cancer cells. Using cell lines, patient-derived xenograft models, and primary
tumors, we investigated the regulation of CSCs and
tumor progression by
chemotherapy-induced factors.Results: In human patients and mice, we detected a
therapy-induced CSC-stimulatory activity in serum, which was attributed to
therapy-associated monocytosis leading to systemic elevation of
monocyte chemoattractant proteins (MCP). The post-NT hematopoietic regeneration in the bone marrow highlighted both altered monocyte-macrophage differentiation and biased commitment of stimulated hematopoietic stem cells toward monocytosis. Chemotherapeutic agents also induce monocyte expression of MCPs through a JNK-dependent mechanism. Genetic and pharmacologic inhibitions of the MCP-CCR2 pathway blocked
chemotherapy's adverse effect on CSCs. Levels of nuclear Notch and ALDH1 were significantly elevated in primary breast
cancers following NT, whereas higher levels of CCR2 in pre-NT
tumors were associated with a poor response to NT.Conclusions: Our data establish a mechanism of
chemotherapy-induced
cancer stemness by linking the cellular events in the bone marrow and
tumors, and suggest pharmacologic inhibition of CCR2 as a potential cotreatment during conventional
chemotherapy in neoadjuvant and adjuvant settings. Clin
Cancer Res; 24(10); 2370-82. ©2018 AACR.