Metastatic breast cancer disease is one of the leading causes of cancer-related death among women worldwide. Meanwhile, it is well-established that the epithelial-mesenchymal transition (EMT) is a major event in the development of cancer metastases. On the other hand, recent studies revealed that Aspirin could play an important role in preventing cancer development and its progression. Herein, we explored the effect of aspirin on breast cancer cells and EMT. We found that aspirin-treatment initiates mesenchymal to epithelial transition, which is the opposite event of EMT; thus, aspirin-treatment can potentially inhibit cancer invasion and metastasis. These data suggest that aspirin could be useful to prevent breast cancer progression as well as other human carcinomas and their metastases.

Breast cancer is the most common type of malignant disease in women worldwide. Currently, breast cancer is the second leading cause of death due to cancer in women. [1] It is estimated that more than 90% of cancer deaths are the result of metastasis, either directly due to tumor involvement of critical organs or indirectly due to complications of therapy to control tumor growth and spread. In view of the limited success of available treatment modalities for metastatic cancer including breast, alternative and complementary preventive strategies need to be explored. Herein, we investigated the effect of aspirin on the epithelial-to-mesenchymal transition (EMT) event, which is considered as a dedifferentiation switch between polarized epithelial cancer cells and motile mesenchymal cells during cancer progression and metastasis; the EMT is characterized by a decrease in the expression of proteins that enhance cell-cell adhesion such as the E-cadherin/catenin complex, as well as an increase in the expression of mesenchymal markers such as vimentin and N-cadherin as well as the activity of certain matrix metalloproteinases. [2]

Aspirin (acetylsalicylic acid [ASA]) is widely used to manage pain, arthritis, and cardiovascular diseases. Epidemiological studies, randomized control trials, and experimental investigation suggest the beneficial effect of ASA in the prevention, progression, and metastatic growth of various cancers, including colon, gastrointestinal cancer, prostate, and breast cancers. [3] The major mechanism is the anti-inflammatory action through the inhibition of COX-1/COX-2 and modulation of the NFκB or STAT3 pathways. [3] In addition, aspirin may activate AMPK, thus affecting notch, Wnt/β-catenin and other signaling pathways.[4],[5] This is particularly significant since the Wnt/β-catenin signaling pathway is a major regulator of EMT. [2]

Herein we report, for the 1 st time, that ASA induces a mesenchymal-epithelial transition (MET) of MCF7 and BT20 breast cancer cells, which could consequently inhibit cell invasion and cancer metastasis. MET is considered as the opposite event of EMT, which can be accompanied by an up-regulation and restoration of the expression patterns of the E-cadherin/catenin complex as well as other cell-cell adhesion proteins. MCF7 and BT20 cells were treated with 5 μM and 10 μM ASA for 2 days. In the absence of treatment, MCF7 and BT20 cells displayed a fibroblast-like (mesenchymal) morphology and formed multilayered disorganized cells. In contrast, as indicated in [Figure 1], ASA-treatment led to a substantial phenotypic conversion from fibroblast-like (mesenchymal) to epithelial phenotype. Cells became more flattened in appearance, and showed an increase in cell-cell contact in comparison with untreated cells and dimethyl sulfoxide (DMSO)-treated cells [Figure 1], which was used to dissolve the ASA (Sigma Chemical Co.). Recently Maity et al. [6] reported that ASA treatment of MCF7 and MDA231 breast cancer cell lines induce a down-regulation of mesenchymal marker (i.e., vimentin), and an up-regulation of epithelial markers (i.e., keratin-19 and E-cadherin); thus blocking cell invasion ability of these cell lines. Accordingly, we demonstrated clearly that ASA initiate MET of MCF7 and BT20 cancer cells.{Figure 1}

Regarding the mechanism of ASA MET induction, we believe that the AMPK and Wnt/β-catenin signaling pathways could be the main routes of this effect. We previously reported that SKI-606, a Src/Abl kinase inhibitor, induce MET, of HeLa and SiHa cervical cancer cells, and consequently reduce cell invasion ability of these cell lines in vitro; this was accompanied by a re-localization of E-cadherin and β-catenin expression patterns from the cytoplasm and nucleus, respectively, to the undercoat cytoplasmic membrane; [7] in addition, we revealed that Src activation converts β-catenin′s role from a cell-cell adhesion molecule to a transcriptional regulator via its interaction with the Tcf/Lef family of transcription factors. [7] Based on this investigation and recent study of Maity et al., [6] we assume that ASA could dephosphorylate Src and consequently β-catenin, via its interaction with receptor tyrosine kinases such as ErbB family members and VEGF-receptor, [8],[9] which is largely expressed in human carcinomas including breast. Thus, ASA can restore the expression pattern of β-catenin to the undercoat membrane to act as a cell-cell molecule, and regulate several genes including epithelial and mesenchymal markers, thereby blocking cell invasion and metastasis via the conversion of EMT into MET. Accordingly, we firmly believe that ASA can be used to prevent human carcinomas progression including breast as well as other malignancies; however, we consider that more molecular and cellular studies are necessary to elucidate the exact mechanistic function of ASA in the conversion of EMT into MET from, which can have a major role to identify new and efficient targets to prevent and/or manage metastatic cancers.

Acknowledgments

We are grateful to Dr. G. Batist for supporting our work. We are thankful to Ms A. Kassab for her critical reading of the manuscript. The research works of Dr. Al Moustafa′s laboratory has been supported by the Canadian Institutes for Health Research, the Cancer Research Society Inc., of Canada, the National Colorectal Cancer Campaign and the Fonds de la Recherche en Santé du Quιbec (FRSQ- Réseau du Cancer).

Financial support and sponsorship

Nil.

Conflict of interest

There are no conflict of interest.