Combination of RAD001 (everolimus) and docetaxel reduces prostate and breast cancer cell VEGF production and tumour vascularisation independently of sphingosine-kinase-1

Abstract

Resistance to docetaxel is a key problem in current prostate and breast cancer management. We have recently discovered a new molecular mechanism of prostate cancer docetaxel chemoresistance mediated by the mammalian target of rapamycin (mTOR)/sphingosine-kinase-1 (SK1) pathway. Here we investigated the influence of this pathway on vascular endothelial growth factor (VEGF) production and tumour vascularisation in hormone resistant prostate and breast cancer models. Immunofluorescent staining of tumour sections from human oestrogen receptor (ER)-negative breast cancer patients showed a strong correlation between phosphorylated P70S6 kinase (mTOR downstream target), VEGF and SK1 protein expression. In hormone-insensitive prostate (PC3) and breast (MDA-MB-231 and BT-549) cancer cell lines the mTOR inhibitor RAD001 (everolimus) has significantly inhibited SK1 and VEGF expression, while low dose (5 nM) docetaxel had no significant effect. In these cell lines, SK1 overexpression slightly increased the basal levels of VEGF, but did not block the inhibitory effect of RAD001 on VEGF. In a human prostate xenograft model established in nude mice, RAD001 alone or in combination with docetaxel has suppressed tumour growth, VEGF expression and decreased tumour vasculature. Overall, our data demonstrate a new mechanism of an independent regulation of SK1 and VEGF by mTOR in hormone-insensitive prostate and breast cancers.

<p>Co-delivery of everolimus and vinorelbine via a tumor-targeted liposomal formulation inhibits tumor growth and metastasis in RCC</p>

“…Everolimus has been shown to possess anti-angiogenic properties as well, though its mode of action is different from other vascular endothelial growth factor receptor (VEGFR)-tyrosin kinase inhibitors 38. Several studies demonstrated that everolimus inhibits the expression of VEGF in tumor cells 52,54. Everolimus is now approved for second- and third-line therapy in patients with advanced RCC, but it did not offer any significant clinical benefit in first-line setting even in combination with bevacizumab 55.…”

Field template-based design and biological evaluation of new sphingosine kinase 1 inhibitors

“…Cell culture was performed as previously described [ 42 , 43 ]. Human breast cancer cell line MDA-MB-231 and murine breast cancer cell line 4T1 were purchased from ATCC (Manassas, VA, USA), and maintained in DMEM with 10% fetal calf serum, 50 U/ml penicillin, 50 µg/ml streptomycin, and 2 mM glutamine (Sigma-Aldrich, St. Louis, MO).…”

Sphingosine Kinase 1 in Breast Cancer—A New Molecular Marker and a Therapy Target

“…This combination inhibited growth of E0771 cells (a mouse mammary adenocarcinoma cell line expressing the ER) in vitro and suppressed the expression of S1P signaling-related genes, STAT3 and IL-6, as well as reducing tumor burden in vivo (119), suggesting that the SK1/S1P/S1PR1 axis plays a role in doxorubicin resistance. It has been shown that in triple negative breast cancer cell lines, MDA-MB-231 and BT-549, mTOR inhibitor RAD001 (everolimus) reduced SK1 expression and sensitized these cells to low-dose (5 nM) docetaxel (122). Furthermore, in an ER-positive patient cohort, higher BMI was positively correlated with the S1P signaling pathway but negatively correlated with the doxorubicin-resistant gene set, suggesting that the FTY720/doxorubicin combination may be particularly useful for ER-positive tumors in obese patients (119).…”

“…Additionally, prolonged SK1 inhibition generates a wide genetic response, including upregulation of multiple prosurvival pathways as well as expression of SK2, which provides cells with missing S1P (149). This again warrants a trial evaluating the use of SK1 inhibitors in combination with other molecular therapy or chemotherapy (122,150), or alternatively one utilizing pan-SK inhibitors, rather than selective SK1 inhibitors. 4) Use of nanocarriers in delivering combination therapies.…”