Simvastatin Prevents Skeletal Metastasis of Breast Cancer by an Antagonistic Interplay between p53 and CD44

Abstract

Substantial data from clinical trials and epidemiological studies show promising results for use of statins in many cancers, including mammary carcinoma. Breast tumor primarily metastasizes to bone to form osteolytic lesions, causing severe pain and pathological fracture. Here, we report that simvastatin acts as an inhibitor of osteolysis in a mouse model of breast cancer skeletal metastasis of human mammary cancer cell MDA-MB-231, which expresses the mutant p53R280K. Simvastatin and lovastatin attenuated migration and invasion of MDA-MB-231 and BT-20 breast tumor cells in culture. Acquisition of phenotype to express the cancer stem cell marker, CD44, leads to invasive potential of the tumor cells. Interestingly, statins significantly decreased the expression of CD44 protein via a transcriptional mechanism. shRNA-mediated down-regulation of CD44 markedly reduced the migration and invasion of breast cancer cells in culture. We identified that in the MDA-MB-231 cells, simvastatin elevated the levels of mutated p53R280K, which was remarkably active as a transcription factor. shRNAderived inhibition of mutant p53R280K augmented the expression of CD44, leading to increased migration and invasion. Finally, we demonstrate an inverse correlation between expression of p53 and CD44 in the tumors of mice that received simvastatin. Our results reveal a unique function of statins, which foster enhanced expression of mutant p53R280K to prevent breast cancer cell metastasis to bone.Statins are potent inhibitors of the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme in the mevalonate pathway for the biosynthesis of cholesterol (1). These compounds have been used for decades as safe and effective drugs in the control of hypercholesterolemia. The mevalonate pathway also produces a number of important end products, which include isoprenoid precursors, ubiquinone, dolichol, and isopentenyladenine (2). Statins also show anti-carcinogenic effects in rodent models of lung, prostate, melanoma, colon, glioma, and mammary tumorigenesis, and beneficial effects of statins have been seen in different cancers, including breast cancer (2, 3). For example, a significant 20% reduction in overall cancer risk was observed in patients with statin use (4). A recent study conducted in women who used statins showed significantly reduced risk of breast cancer as compared with nonusers (5). Moreover, an independent study of women who used statins for more than 4 years reported a significantly lower risk of breast cancer in this group (6).Several distinct mechanisms have been proposed whereby statins block tumor cell proliferation and induce apoptosis. For example, inhibition of geranylgeranyl pyrophosphate and farnesyl pyrophosphate production by statins prevents the post-translational modification of Rho and Ras GTPases necessary for their membrane localization (2). Rho proteins regulate the proliferative and invasive potential of various tumor cells, including breast cancer cells (2). Thus, suppression of geranylge...

Interplay of mevalonate and Hippo pathways regulates RHAMM transcription via YAP to modulate breast cancer cell motility

“…BCCMI has been shown to be inhibited by simvastatin (25), and our experiments of transwell migration assays using MDA-MB-231 human mammary tumor cells and 4T1 mouse mammary tumor cells confirmed this observation (Fig. S1).…”

“…Those promising preclinical results have led to at least 18 reported phase I and I/II clinical trials (23). In breast cancer, statins prevented metastasis by inhibiting CD44 expression through promoting p53 expression (25). Statins enhance the effects of a number of chemotherapeutic drugs with only a few exceptions, and also increase the chemotherapeutic sensitivity of multidrug resistance cells.…”

“…Transwell cell migration and invasion assays and generation of the mouse model of MDA-MB-231 cellderived tumor and treatment with simvastatin were performed essentially as described previously (25). All animal studies were carried out according to the protocols approved by the Administrative Committee on Animal Research of the Graduate School at Shenzhen, Tsinghua University.…”

“…Statins could trigger tumor-specific apoptosis by blocking protein geranylgeranylation, leading to disrupted membrane localization and function of the Ras superfamily including CDC42 and Rac and Rho GTPase (22,23), as well as disorganization of actin stress fibers (24). Simvastatin was shown to foster enhanced expression of mutant p53 to down-regulate CD44 expression, therefore preventing breast cancer cell metastasis to bone (25). Furthermore, simvastatin inactivated NF-κB, leading to derepression of PTEN and repression of Bcl-xl to prevent breast cancer cell growth (26).…”

“…In the present study, we have sought to address these and related issues in the context of breast cancer. We have focused on molecular and cellular investigations by using a couple of highly metastatic breast cancer cell lines and a nontumor cell line, and conducted selective and relevant in vivo investigations with human breast tumor tissues and its xenografts mouse model, as previous animal model studies had established that the metastasis of breast cancer was inhibited by simvastatin (25). We find that the mevalonate pathway promotes, and simvastatin inhibits, the expression of RHAMM, which is necessary for ERK phosphorylation and BCCMI, via a transcriptional mechanism mediated directly by YAP.…”