ICAM1 is also considered a target in triple-negative breast malignancy [33]

ICAM1 is also considered a target in triple-negative breast malignancy [33]. Tumor-associated fibroblasts enhanced tumor growth and vasculature as well as increased expression of the pro-angiogenic factors. These effects were blunted by dn-p38. Metadata analysis showed elevated expression of p38 target genes in breast cancers and Rabbit Polyclonal to 5-HT-2B this was an unfavorable marker of disease recurrence and poor-outcome. Thus, our study demonstrates that tumor p38MAPK signaling promotes breast carcinoma growth, invasive and metastatic capacities. Importantly, p38 enhances carcinoma vascularization by facilitating expression and deposition of pro-angiogenic factors. These results argue that p38MAPK is usually a valuable target for Pargyline hydrochloride anticancer therapy affecting tumor vasculature. Anti-p38 drugs may provide new therapeutic strategies against breast malignancy, including metastatic disease. gene is usually ubiquitously expressed at high levels [22]. Recent studies with small-molecule inhibitors targeting p38-alpha/beta isoforms have shown promising results in preclinical studies and several anti-p38 drugs are under evaluation in clinical settings [27]. In preclinical animal models, p38-alpha/beta inhibitors have significantly reduced tumor xenograft growth and metastasis [25, 28]. Despite of these advancements, the role of tumor p38MAPK signaling in the breast carcinoma TME is still poorly understood. The current study examined the contribution of tumor p38MAPK to breast carcinoma progression. We found that disruption of p38MAPK signaling in breast cancer cells by a kinase-inactive p38/MAPK14-AGF mutant (dn-p38) delayed tumor growth and formation of spontaneous metastasis in xenograft models. Immuno-histological analysis of tumor xenografts revealed a significant reduction in tumor vasculature in the dn-p38 xenografts. Studies of tumor-fibroblast interactions showed that fibroblasts enhanced tumor vasculature and growth of the control tumors, whereas this effect was lost in dn-p38 tumor xenografts. Mechanistic studies revealed that inactivation of p38 decreases expression of pro-angiogenic extracellular factors VEGFA, IL8, HBEGF and matrix protein Fibronectin. These findings indicate that tumor p38MAPK facilitates tumor vascularization by enhancing production and matrix-deposition of pro-angiogenic factors. RESULTS p38MAPK signaling contributes to tumor cell invasion and metastatic potential Systemic administration of selective p38-alpha/beta isoform inhibitors reduces both primary tumor growth and metastasis in breast carcinoma models [29, 30]. Here we asked whether inactivation of p38MAPK in breast malignancy cells would influence tumor growth and the tumor microenvironment. Disruption of p38MAPK signaling was achieved by expression of a kinase-inactive p38MAPK-AGF mutant (a dominant-negative p38, dn-p38) in breast malignancy MDA-MB-231 cell line, established from a patient with metastatic triple-negative breast malignancy (TNBC). Dn-p38 strategy better mimics a treatment with kinase inhibitors compared to a depletion strategy using RNA interference or gene-disruption approaches. Tumor cells were infected with empty-vector control and dn-p38 retroviruses, which also encoded enhanced green-fluorescence protein (EGFP) translated from an internal ribosome entry site (IRES) [24]. EGFP-positive cell populations were selected for further studies. Immunoblot analysis of EGFP-positive cells revealed expression of FLAG-tagged dn-p38 protein comparable with endogenous p38MAPK (Physique ?(Figure1A).1A). Dn-p38 effectively blocked phosphorylation of HSP27, a well-known p38 target, in response to TGF-1 treatment (Physique ?(Figure1A).1A). Dn-p38 also reduced levels of active phosphorylated Pargyline hydrochloride p38MAPK but did not affect phosphorylation of Smad2, as expected (Physique ?(Figure1A).1A). Pargyline hydrochloride Dn-p38 did not affect phosphorylation of ERK (Supplementary Physique 1). These findings argue that dn-p38 selectively inactivated p38MAPK signaling. Open in a separate window Physique 1 p38MAPK contributes to breast carcinoma invasion and metastasis(A) Immunoblotting of whole-cell lysates from breast malignancy MDA-MB-231 cells transduced with empty-vector control (EGFP) or Flag-tagged p38MAPK-AGF (dn-p38). Cells were treated with 2 ng/mL TGF-1 for the indicated occasions. (B) Invasion of MDA-MB-231 cells tested using Matrigel-covered transwells. Assays were done in triplicate and repeated at least twice. (C) Lung surface colonies of EGFP and dn-p38 MDA-MB-231 cells after tail-vein injection of tumor cells into female SCID mice, 6 mice/group). **, P 0.01 Next, we assessed invasive and metastatic potential of EGFP- and dn-p38 cell populations. Dn-p38 reduced invasion and lung metastasis in a tail-vein experimental metastasis model (Physique 1B, 1C). The latter finding was further validated using MDA-MB-231 cells expressing a kinase-inactive MKK6-AL mutant form of MKK6 (dn-MKK6) [24], a p38MAPK activating kinase (Physique.