Since cancer metastases are the major reason for the mortality of cancer patients, prevention of metastases will significantly extend life of cancer patients. Here we showed that dietary supplement BD markedly prevented breast-to-lung cancer metastases in an animal model of metastatic human breast cancer. Although we observed a modest but significant inhibition in tumor volume over time between control and BD treatment groups, this effect was not so dramatic. Nevertheless, BD treatment prevented breast-to-lung cancer metastases by 70%. The in vivo systemic effect of BD, after an oral application of BD, can protect against breast-to-lung cancer metastasis as we are demonstrating here.
BD is a polybotanical compound and some of its isolated components suppressed cancer metastases in vivo
. For example, dietary administration of curcumin decreased the incidence of breast-to-lung cancer metastasis in nude mice (24
). Apigenin, biologically active compound from Scutellaria barbata
prevented hepatocyte growth factor induced lung metastasis of breast cancer cells (25
). Protein-bound polysaccharide isolated from Coriolus versicolor
, PSK (Krestin) inhibited lung metastasis in mice (26
), and when combined with chemotherapy, PSK significantly prolonged survival of patients with metastatic gastric cancer (27
). Isolated polysaccharides or an extract from Phellinus linteus
suppressed pulmonary metastasis of melanoma cells in mice (28
). In addition, triterpenoid fraction from Ganoderma lucidum
inhibited liver metastasis (30
), and G. lucidum
in diet or i.p. injection of isolated ganoderic acid T suppressed lung metastasis, respectively (31
). Finally, an oral administration of DIM markedly inhibited lung metastasis of murine cancer cells in mice (33
). Therefore, in agreement with our in vitro
study with BD (6
) combined anti-metastatic effects of isolated components in BD could result in the prevention of breast-to-lung cancer metastasis in vivo
Urokinase plasminogen activator (uPA; PLAU
gene) is one of the major proteins involved in the invasive behavior (adhesion, migration and invasion) of cancer cells and cancer metastasis (34
). Moreover, mice with knockout PLAU
gene demonstrated slower growth and fewer metastases of human xenografted breast cancer cells in immunodeficient mice (36
). Overexpression of the chemokine receptor CXCR4
was originally detected in human breast cancer cells, malignant breast tumors and metastases (37
). Inhibiting CXCR4 expression in breast cancer cells, using different strategies (e.g., siRNA silencing, phenotypic CXCR4
knockout, peptide inhibitor of protein kinease-α), also suppressed breast cancer metastasis (38
). Therefore, targeting PLAU
expression with natural compounds should result in the suppression of breast to lung cancer metastasis. Indeed, here we show that 70% of the inhibition of breast-to-lung cancer metastases is associated with the downregulation of expression of PLAU
in primary tumors in mice treated with BD. Moreover, the relative expression of PLAU
in primary tumors is a predictive marker of breast-to-lung cancer metastasis because we have identified significant increase of these genes in animals with metastases.
As mentioned above, the effect of BD on the growth of primary tumors was significant albeit modest. However, we observed a dominant effect in the inhibition of breast-to-lung cancer metastases. Since BD mainly prevents metastases, combination therapy with other agents directly targeting tumor growth and/or surgical tumor resection could be considered for the alternative treatment of invasive breast cancers.
In our study we induced primary tumors and breast-to-lung cancer metastasis with MDA-MB-231 cells. These cells are characterized as basal-like/triple-negative breast cancer cells; lacking expression of estrogen receptor-α (ER), progesterone receptor (PR) and ErbB2/neu (HER2), which represent a highly aggressive breast cancer subtype, that is resistant to treatment and is associated with poor prognosis (41
). Therefore, BD inhibits breast-to-lung cancer metastases in a model based on breast cancer cells which do not respond to the targeted receptor treatments (e.g., trastumazab and hormonal treatments) (42
), suggesting BD as a natural dietary agent for the treatment of triple-negative therapy resistant breast cancer cells.
In conclusion, our data demonstrate that the novel dietary supplement BreastDefend (BD): i) is not toxic in vivo at the concentration 100 mg/kg of body weight, and ii) inhibits growth of breast tumors and breast-to-lung cancer metastases in mice. Our data suggest that BD specifically targets expression of PLAU and CXCR4 in triple-negative and highly aggressive breast tumors in vivo. In conclusion, BD may be considered as novel polybotanical preparation for the prevention and alternative therapy of metastatic breast cancer.