ABSTRACT
Active cancer-associated fibroblasts (CAFs), which constitute the most preponderant cell type in breast tumors, contribute actively to all aspects of cancer progression, stimulate recurrence, and restrain drug sensitivity. In the present study, we tested the effect of the selective JAK/STAT3 inhibitor cucurbitacin I (JSI-124) on active breast CAFs. We have shown that JSI-124 at non-cytotoxic concentration (20 nM) can inhibit the IL-6/STAT3/NF-κB positive feedback loop in breast myofibroblasts, which enabled persistent inactivation of these cells. Interestingly, JSI-124 treatment suppressed the paracrine promotion of the epithelial-to-mesenchymal transition (EMT) process and the pro-migratory/-invasive and -proliferative effects of CAFs on breast cancer cells in vitro. Similarly, JSI-124 inhibited the capacity of CAF cells in promoting tumor growth, EMT, stemness as well as angiogenesis in orthotopic humanized breast cancer tumors. Together, these findings indicate that JSI-124-dependent inhibition of STAT3 could be of great therapeutic value for the treatment of breast cancer through targeting cancer cells as well as their growth supportive stromal fibroblasts and blood vessels. This could pave the path to developing a precise CAF-targeted anticancer therapy.
Subject(s)
Breast Neoplasms/drug therapy , Cancer-Associated Fibroblasts/drug effects , Feedback, Physiological/drug effects , STAT3 Transcription Factor/antagonists & inhibitors , Triterpenes/administration & dosage , Animals , Breast Neoplasms/metabolism , Cancer-Associated Fibroblasts/metabolism , Cell Line, Tumor , Epithelial-Mesenchymal Transition/drug effects , Female , Gene Expression Regulation, Neoplastic/drug effects , Humans , Interleukin-6/metabolism , Mice , NF-kappa B/metabolism , Triterpenes/pharmacology , Xenograft Model Antitumor AssaysABSTRACT
Increasing evidence supports the critical role of active stromal adipocytes in breast cancer development and spread. However, the mediators and the mechanisms of action are still elusive. We show here that cancer-associated adipocytes (CAAs) isolated from 10 invasive breast carcinomas are proinflammatory and exhibit active phenotypes, including higher proliferative, invasive, and migratory capacities compared to their adjacent tumor-counterpart adipocytes (TCAs). Furthermore, all CAAs secreted higher level of interleukin-8 (IL-8), which is critical in mediating the paracrine procarcinogenic effects of these cells. Importantly, ectopic expression of IL-8 in TCA cells activated them and enhanced their procarcinogenic effects both in vitro, in a STAT3-dependent manner, and in vivo In contrast, inhibition of the IL-8 signaling using specific short hairpin RNA, anti-IL-8 antibody, or reparixin suppressed the active features of CAAs, including their non-cell-autonomous tumor-promoting activities both on breast luminal cells and in orthotopic tumor xenografts in mice. IL-8 played also an important role in enhancing the proangiogenic effects of breast adipocytes. These results provide clear indication that IL-8 plays key roles in the activation of breast CAAs and acts as a major mediator for their paracrine protumorigenic effects. Thus, targeting CAAs by inhibiting the IL-8 pathway could have great therapeutic value.
Subject(s)
Adipocytes/immunology , Breast Neoplasms/metabolism , Interleukin-8/immunology , Adipocytes/pathology , Angiogenesis Inducing Agents/immunology , Angiogenesis Inducing Agents/metabolism , Animals , Breast Neoplasms/blood supply , Breast Neoplasms/immunology , Breast Neoplasms/pathology , Carcinogenesis/immunology , Carcinogenesis/metabolism , Cell Line, Tumor , Cell Movement/physiology , Cell Transformation, Neoplastic , Female , Fibroblasts/metabolism , Fibroblasts/pathology , Heterografts , Humans , MCF-7 Cells , Mice , Neoplasm Invasiveness , Neovascularization, Pathologic/metabolism , Primary Cell Culture , STAT3 Transcription Factor/immunology , Signal Transduction , Stromal Cells/metabolism , Stromal Cells/pathologyABSTRACT
The IL-6/STAT3/NF-κB positive feedback loop links inflammation to cancer and maintains cells at a transformed state. Similarly, cancer-associated myofibroblats remains active even in absence of cancer cells. However, the molecular basis of this sustained active state remains elusive. We have shown here that breast cancer cells and IL-6 persistently activate breast stromal fibroblasts through the stimulation of the positive IL-6/STAT3/NF-κB feedback loop. Transient neutralization of IL-6 in culture inhibited this signaling circuit and reverted myofibrobalsts to a normalized state, suggesting the implication of the IL-6 autocrine feedback loop as well. Importantly, the IL-6/STAT3/NF-κB pro-inflammatory circuit was also active in cancer-associated fibroblasts isolated from breast cancer patients. Transient inhibition of STAT3 by specific siRNA in active fibroblasts persistently reduced the level of the RNA binding protein AUF1, blocked the loop and normalized these cells. Moreover, we present clear evidence that AUF1 is also part of this positive feedback loop. Interestingly, treatment of breast myofibroblasts with caffeine, which has been previously shown to persistently inhibit active breast stromal fibroblasts, blocked the positive feedback loop through potent and sustained inhibition of STAT3, AKT, lin28B and AUF1. These results indicate that the IL-6/STAT3/NF-κB positive feedback loop includes AUF1 and is responsible for the sustained active status of cancer-associated fibroblasts. We have also shown that normalizing myofibroblasts, which could be of great therapeutic value, is possible through the inhibition of this procarcinogenic circuit.
