Lung Fibroblasts Modulate Human Breast Cancer Cell Sensitivity to Chemotherapy and Autophagy Inhibition in a 3‐Dimensional Organotypic Co‐Culture Model

Abstract

Fibroblasts are one cell type present in the tumor microenvironment (TME) which have been linked to several tumor growth and metastasis promoting activities. Recent data suggest that the molecular mechanisms underlying these metastasis‐promoting effects of the TME share significant overlap with those which mediate therapeutic resistance. Despite this, very few studies have evaluated the contributions of stromal cells on potential extrinsic mechanisms of cancer chemo‐resistance. Periostin (POSTN) is an extracellular matrix protein whose expression by lung fibroblasts has been shown to promote metastatic colonization and induction of a cancer stem cell (CSC) phenotype in a mouse model of breast cancer metastasis. However, the potential effects of lung fibroblasts (LFs) and POSTN in mediating tumor cell survival and chemoresistance in human breast cancer cells (BCCs) has not been evaluated. Therefore, we evaluated the effects of primary human LFs and recombinant POSTN on human BCC sensitivity to doxorubicin (DOX) and pharmacological inhibition of autophagy utilizing a modified 3D organotypic co‐culture model. Initial screening of a panel of six human breast cancer cell lines demonstrated that while rPOSTN induced BCC survival/proliferation under low‐serum conditions, it had no effect on BCC resistance to the autophagy inhibitor chloroquine (CQ). However, compared to standard 2‐D monolayer culture, 3D culture of either human BCCs or LFs alone induced resistance of both LFs and triple‐negative breast cancer (TNBC) cell lines to autophagy inhibition with CQ. Interestingly, the addition of primary human LFs into this 3D co‐culture system re‐sensitized TNBC cell lines to CQ, to a degree similar to that observed in standard 2‐D mono‐culture. In contrast, DOX sensitivity was not altered by 3D mono‐culture of any of the human BCC lines screened, while the addition of LFs induced DOX‐resistance in the luminal, ER+ cell line, T47D. These results suggest that the effect of lung fibroblasts on human BCC sensitivity to chloroquine and doxorubicin may be dependent on breast cancer molecular subtype and provide evidence for lung fibroblast‐mediated regulation of autophagy in human BCCs.Support or Funding InformationThe authors would like to acknowledge the following sources of funding support: NIH‐NCI K01ODO22982 (DP Regan) and NIH‐NCI 1R01CA190170 (DL Gustafson).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.