Extract of Caulis Spatholobi, a novel blocker targeting tumor cell-induced platelet aggregation, inhibits breast cancer metastasis

Metastasis of breast cancer is the vital step for malignant progression. During such a process, hematogenous metastasis is an indispensable approach for the dissemination of cancer cells. A platelet, contributes to hypercoagulable state, and is also identified the crucial factor in the coagulation system for supporting metastasis. Therefore, the relationship of a platelet and a tumor cell plays a critical role in tumor cell metastasis. Consequently, inhibiting tumor cell-induced platelet aggregation (TCIPA) is recongnized as a crucial target on suppression of tumor metastasis such as aspirin (ASA). Under such circumstance, here we report that, through dissociating the tumor-platelet (T-P) complex, 80% ethanol extracts of Caulis Spatholobi (SET) successfully alleviated the hypercoagulation state, thereby reducing tumor metastasis and improving the prospects of survival in breast cancer cell model. Through MTT and anti-aggregation assay stimulated by ADP, we detected the optimum treatment time and the optimum dose of SET. By using confocal microscopy, we observed that SET can strongly block the formation of T-P complex in vitro. The result was further quantified and confirmed by the FACS analysis. The fluorescent value of T-P complex was obviously decreased in the drug-treated groups. In vivo, 4T1 cells were injected through the mouse tail vein for dynamic visualization by small animal imaging system. The metastatic intensity was quantified and the survival curve was analyzed. Additionally, general observation and hematoxylin and eosin (H&E) staining of lung tissue was performed. SET exerted an obvious effect on the inhibition of metastasis and increasing the survival rate of mice. For the molecular mechanism study of anti-TCIPA, zymography and RT-PCR assay preliminarily revealed the molecular mechanism of SET in the regulation of P-T interaction. Collectively, through drug efficacy identification and pharmacological revealing, we have obtained a promising candidate for the interference of breast metastasis by suppressing TCIPA, which will be beneficial for clinical cancer treatment.