Abstract
IntroductionStudying cancer tumors’ microenvironment may reveal a novel role in driving cancer progression and metastasis. The biological interaction between stromal (mesenchymal) stem cells (MSCs) and cancer cells remains incompletely understood. Herein, we investigated the effects of tumor cells’ secreted factors as represented by a panel of human cancer cell lines (breast (MCF7 and MDA-MB-231); prostate (PC-3); lung (NCI-H522); colon (HT-29) and head & neck (FaDu)) on the biological characteristics of MSCs.MethodsMorphological changes were assessed using fluorescence microscopy. Changes in gene expression were assessed using Agilent microarray and qRT-PCR. GeneSpring 12.1 and DAVID tools were used for bioinformatic and signaling pathway analyses. Cell migration was assessed using a transwell migration system. SB-431542, PF-573228 and PD98059 were used to inhibit transforming growth factor β (TGFβ), focal adhesion kinase (FAK), and mitogen activated protein kinase kinase (MAPKK) pathways, respectively. Interleukin-1β (IL1β) was measured using ELISA.ResultsMSCs exposed to secreted factors present in conditioned media (CM) from FaDu, MDA-MB-231, PC-3 and NCI-H522, but not from MCF7 and HT-29, developed an elongated, spindle-shaped morphology with bipolar processes. In association with phenotypic changes, genome-wide gene expression and bioinformatics analysis revealed an enhanced pro-inflammatory response of those MSCs. Pharmacological inhibitions of FAK and MAPKK severely impaired the pro-inflammatory response of MSCs to tumor CM (approximately 80% to 99%, and 55% to 88% inhibition, respectively), while inhibition of the TGFβ pathway was found to promote the pro-inflammatory response (approximately 3-fold increase). In addition, bioinformatics and pathway analysis of gene expression data from tumor cell lines combined with experimental validation revealed tumor-derived IL1β as one mediator of the pro-inflammatory phenotype observed in MSCs exposed to tumor CM.MSCs exhibited significant tropism toward secreted factors from the aforementioned tumor cell lines, while both normal and MSCs exposed to tumor CM were capable of attracting human peripheral blood mononuclear cells (PBMCs).ConclusionsOur data revealed tumor-derived IL1β as one mediator of the pro-inflammatory response in MSCs exposed to tumor CM, which was found to be positively regulated by FAK and MAPK signaling and negatively regulated by TGFβ signaling. Thus, our data support a model where MSCs could promote cancer progression through becoming pro-inflammatory cells within the cancer stroma.
Highlights
Studying cancer tumors’ microenvironment may reveal a novel role in driving cancer progression and metastasis
We identified tumor-derived IL1β as the prominent cytokine responsible for induction of inflammatory response in MSCs and signaling via focal adhesion kinase (FAK) and, to lesser extent, mitogen activated protein kinase kinase (MAPKK), as key positive regulators of an inflammatory response, while transforming growth factor β (TGFβ) signaling was found to inhibit the response of MSCs to tumor conditioned media (CM)
Effects of conditioned media on MSCs morphology and gene expression Initially, we assessed the effect of CM from a FaDu tumor cell line on MSC morphology
Summary
Studying cancer tumors’ microenvironment may reveal a novel role in driving cancer progression and metastasis. We investigated the effects of tumor cells’ secreted factors as represented by a panel of human cancer cell lines (breast (MCF7 and MDA-MB-231); prostate (PC-3); lung (NCI-H522); colon (HT-29) and head & neck (FaDu)) on the biological characteristics of MSCs. Stromal (mesenchymal) stem cells (MSCs), referred to as stromal cells, are multipotent cells which are present within the stroma of bone marrow and probably other organs and capable of differentiating into the three canonical lineages: osteoblasts, adipocytes and chondrocytes [1]. Stromal (mesenchymal) stem cells (MSCs), referred to as stromal cells, are multipotent cells which are present within the stroma of bone marrow and probably other organs and capable of differentiating into the three canonical lineages: osteoblasts, adipocytes and chondrocytes [1] Aside from their differentiation potential, MSCs are capable of migrating to injured tissues and contributing to tissue regeneration [2,3,4]. Understanding the settings under which MSCs exert promoting versus inhibitory effects on tumor growth and metastasis is currently under intensive investigation
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