Inoculated mammary carcinoma-associated fibroblasts: contribution to hormone independent tumor growth

Abstract

Background: Increasing evidence has underscored the role of carcinoma associated fibroblasts (CAF) in tumor growth. However, there are controversial data regarding the persistence of inoculated CAF within the tumors. We have developed a model in which murine metastatic ductal mammary carcinomas expressing estrogen and progesterone receptors transit through different stages of hormone dependency. Hormone dependent (HD) tumors grow only in the presence of progestins, whereas hormone independent (HI) variants grow without hormone supply. We demonstrated previously that CAF from HI tumors (CAF-HI) express high levels of FGF-2 and that FGF-2 induced HD tumor growth in vivo. Our main goal was to investigate whether inoculated CAF-HI combined with purified epithelial (EPI) HD cells can induce HD tumor growth.Methods: Purified EPI cells of HD and HI tumors were inoculated alone, or together with CAF-HI, into female BALB/c mice and tumor growth was evaluated. In another set of experiments, purified EPI-HI alone or combined with CAF-HI or CAF-HI-GFP were inoculated into BALB/c or BALB/c-GFP mice. We assessed whether inoculated CAF-HI persisted within the tumors by analyzing inoculated or host CAF in frozen sections of tumors growing in BALB/c or BALB/c-GFP mice. The same model was used to evaluate early stages of tumor development and animals were euthanized at 2, 7, 12 and 17 days after EPI-HI or EPI-HI+CAF-HI inoculation. In angiogenesis studies, tumor vessels were quantified 5 days after intradermal inoculation. Results:We found that admixed CAF-HI failed to induce epithelial HD tumor growth, but instead, enhanced HI tumor growth (p < 0.001). Moreover, inoculated CAF-HI did not persist within the tumors. Immunofluorescence studies showed that inoculated CAF-HI disappeared after 13 days. We studied the mechanisms by which CAF-HI increased HI tumor growth, and found a significant increase in angiogenesis (p < 0.05) in the co-injected mice at early time points.Conclusions: Inoculated CAF-HI do not persist within the tumor mass although they play a role during the first stages of tumor formation promoting angiogenesis. This angiogenic environment is unable to replace the hormone requirement of HD tumors that still need the hormone to recruit the stroma from the host.

&#945;2-Adrenoceptors Enhance Cell Proliferation and Mammary Tumor Growth Acting Through both the Stroma and the Tumor Cells

“…We are not able at the present stage of the investigation to assess the origin of these fibroblasts. A murine origin has been described for the CAF [8,[33][34]. IBH-6 epithelial tumor cells continue to express in vivo the 2B and 2C subtypes, already described in cell culture [17].…”

Cancer-Associated Fibroblasts: Their Characteristics and Their Roles in Tumor Growth

“…FGFs have been reported to promote angiogenesis independently of VEGF [ 71 , 81 ]. Giulianelli et al demonstrated that CAFs from hormone-independent tumors express higher levels of FGF-2 than CAFs from hormone-dependent tumors in breast cancer [ 82 , 83 ]. SDF-1 secreted by CAFs also contributes to angiogenesis.…”

Ionizing radiation abrogates the pro-tumorigenic capacity of cancer-associated fibroblasts co-implanted in xenografts

“…Among the possible mechanisms behind CAF-mediated tumor growth regulation in vivo , it has been frequently observed an enhancement of angiogenesis during early phases of tumor formation via secretion of miscellaneous CAF-derived factors, including SDF-1/CXCL12 35 , CXCL14 39 , FGF-2 40 41 , PDGF 42 , IGF2 43 , TGFβ 44 45 or CTGF 46 . Alternative suggested mechanisms are increased deposition of basement membrane components in tumors 30 , expression of fibroblast activation protein (FAP-1) 47 , metalloproteinase 2 (MMP-2) 48 or cofilin-1 and IL-6 49 .…”