Hypoxia Inducible Factors Modify Collagen I Fibers in MDA-MB-231 Triple Negative Breast Cancer Xenografts

Abstract

Hypoxia inducible factors (HIFs) are transcription factors that mediate the response of cells to hypoxia. HIFs have wide-ranging effects on metabolism, the tumor microenvironment (TME) and the extracellular matrix (ECM). Here we investigated the silencing effects of two of the three known isoforms, HIF-1α and HIF-2α, on collagen 1 (Col1) fibers, which form a major component of the ECM of tumors. Using a loss-of-function approach for HIF-1α or 2α or both HIF-1α and 2α, we identified a relationship between HIFs and Col1 fibers in MDA-MB-231 tumors. Tumors derived from MDA-MB-231 cells with HIF-1α or 2α or both HIF-1α and 2α silenced contained higher percent fiber volume and lower inter-fiber distance compared to tumors derived from empty vector MDA-MB-231 cells. Depending upon the type of silencing, we observed changes in Col1 degrading enzymes, and enzymes involved in Col1 synthesis and deposition. Additionally, a reduction in lysyl oxidase protein expression in HIF-down-regulated tumors suggests that more non-cross-linked fibers were present. Collectively these results identify the role of HIFs in modifying the ECM and the TME and provide new insights into the effects of hypoxia on the tumor ECM.

Novel Prognostic Markers in Triple-Negative Breast Cancer Discovered by MALDI-Mass Spectrometry Imaging

“…Of the other identified proteins associated with breast cancer, COL1A1 and COL1A2, the two components of type I collagen, were shown to be upregulated in invasive breast cancer, with a potential role in spinal metastasis, although not proposed as potential targets (40). In contrast, another study found that type 1 collagen fibers increased in human MDA-MB-231 TNBC xenograft tumors when the hypoxia factors HIF-1α or HIF-2α were downregulated (41), consistent with the earlier finding of reduced collagen fibers in hypoxic tumor regions (42), but apparently contradicting a role for type 1 collagen in TNBC invasion and metastasis. Since metastases from ER-/PR- breast tumors are reportedly less likely to be skeletal compared to those from receptor-positive tumors (43), the precise importance of COL1A1/COL1A2 upregulation in TNBC remains unclear.…”

Tumor stiffness measured by shear wave elastography correlates with tumor hypoxia as well as histologic biomarkers in breast cancer

“…Tumor stiffness assessment before or during treatment was significantly associated with the response to neoadjuvant chemotherapy in breast cancer patients [35][36][37]. Production of collagen and increased collagen crosslinking in the ECM, of which collagen is a major component, in the hypoxic tumor microenvironment promote tumor stiffness, encourage tumor cell dissemination, and induce drug resistance [2,14,15,18,19,38]. Thus, tumor stiffness affects the prognostic outcomes and drug response in cancer patients.…”

Elevated preoperative serum levels of collagen I carboxyterminal telopeptide predict better outcome in early-stage luminal-B-like (HER2-negative) and triple-negative subtypes of breast cancer

“…6 Col1 degradation is mostly due to matrix metalloproteinases MMP-1 and MMP-14. 29 In a recent paper, Goggins et al 30 suggested that a decrease of MMP-1 and MMP-14 in HIF-silenced TNBC cells would prevent Col1 degradation and increase the amount of type I collagen fibers. Also, a reduction in lysyl oxidase (LOX) protein expression in HIF-downregulated tumors suggested that more non-crosslinked collagen I fibers are present despite an overall increase in fiber density.…”