Caffeine Mediates Sustained Inactivation of Breast Cancer-Associated Myofibroblasts via Up-Regulation of Tumor Suppressor Genes

Abstract

BackgroundActive cancer-associated fibroblasts (CAFs) or myofibroblasts play important roles not only in the development and progression of breast carcinomas, but also in their prognosis and treatment. Therefore, targeting these cells through suppressing their supportive procarcinogenic paracrine effects is mandatory for improving the current therapies that are mainly targeting tumor cells. To this end, we investigated the effect of the natural and pharmacologically safe molecule, caffeine, on CAF cells and their various procarcinogenic effects.Methodology/Principal FindingsWe have shown here that caffeine up-regulates the tumor suppressor proteins p16, p21, p53 and Cav-1, and reduces the expression/secretion of various cytokines (IL-6, TGF-β, SDF-1 and MMP-2), and down-regulates α-SMA. Furthermore, caffeine suppressed the migratory/invasiveness abilities of CAF cells through PTEN-dependent Akt/Erk1/2 inactivation. Moreover, caffeine reduced the paracrine pro-invasion/−migration effects of CAF cells on breast cancer cells. These results indicate that caffeine can inactivate breast stromal myofibroblasts. This has been confirmed by showing that caffeine also suppresses the paracrine pro-angiogenic effect of CAF cells through down-regulating HIF-1αand its downstream effector VEGF-A. Interestingly, these effects were sustained in absence of caffeine.Conclusion/SignificanceThe present findings provide a proof of principle that breast cancer myofibroblasts can be inactivated, and thereby caffeine may provide a safe and effective prevention against breast tumor growth/recurrence through inhibition of the procarcinogenic effects of active stromal fibroblasts.

The inflammatory/cancer-related IL-6/STAT3/NF-κB positive feedback loop includes AUF1 and maintains the active state of breast myofibroblasts

“…We have recently shown that caffeine mediates sustained inactivation of breast cancer-associated myofibroblasts [15]. Therefore, we sought to investigate whether this sustained effect is mediated through the inhibition of the IL-6/STAT3/NF-κB loop.…”

“…The mRNA level of AUF1, another target of STAT3, was also persistently reduced in response to caffeine (Figure 6B). This clearly shows that caffeine blocks the IL-6/STAT3/NF-κB positive feedback loop, which explains its observed sustained effect on active breast stromal fibroblasts [15]. …”

“…This could allow sort of normalization of active stromal fibroblasts, which may have great anti-cancer effects. In fact, we have shown that caffeine, which mediates sustained inactivation of CAF cells [15], inhibits the positive feedback loop. This provides clear explanation for the persistent inhibitory effect of caffeine on CAF cells [15].…”

“…In fact, we have shown that caffeine, which mediates sustained inactivation of CAF cells [15], inhibits the positive feedback loop. This provides clear explanation for the persistent inhibitory effect of caffeine on CAF cells [15]. This indicates that caffeine could be of great therapeutic value via targeting the carcinogenic and metastatic Lin28B/Let-7b axis in active breast stromal fibroblasts and also inhibits the link between inflammation and cancer.…”

“…Interestingly, it has been recently shown that natural products such as curcumin and caffeine can persistently normalize the active status of myofibroblasts and inhibit their pro-carcinogenic effects, suggesting that the transactivation of these cells is reversible. While curcumin effect was mediated through the induction of senescence, the molecular mechanisms that underlay the sustained inhibitory effects of caffeine on myofibroblats are still remain unclear [15, 16]. Caffeine increased the expression of the tumor suppressor proteins p16, p21 and p53, and repressed the expression/secretion of various procarcinogenic cytokines such as SDF1, IL-6 and TGF-β1 in active breast fibroblasts [15].…”