possible progress in prevention of brain mets w mTor inhibitor & MEK inhibitor combo!

[Lani]

not done in people yet and done w triple negative vs. her2+ bc so far, but principle seems sound since mTor inhibitor which has previously been shown to be helpful in her2+ bc crosses the blood-brain barrier

Breast Cancer Res Treat. 2011 Mar 11. [Epub ahead of print]
The effect of mTOR inhibition alone or combined with MEK inhibitors on brain metastasis: an in vivo analysis in triple-negative breast cancer models.
Zhao H, Cui K, Nie F, Wang L, Brandl MB, Jin G, Li F, Mao Y, Xue Z, Rodriguez A, Chang J, Wong ST.

Departments of Radiology and Pathology, Medical Systems Biology Laboratory, Bioengineering and Bioinformatics Program, The Methodist Hospital Research Institute, Weill Medical College, Cornell University, 6670 Bertner Avenue, R6-211, Houston, TX, 77030, USA.
Abstract
mTOR inhibitor rapamycin and its analogs are lipophilic, demonstrate blood-brain barrier penetration, and have shown promising antitumor effects in several types of refractory tumors. We thus try to explore the therapeutic effects of mTOR inhibitors on brain metastasis models. We examined the effects of different dose of mTOR inhibitors (rapamycin, Temsirolimus-CCI-779) on cell invasion in two brain metastatic breast cancer cell lines (MDA-MB231-BR and CN34-BrM2). Antibody microarray and immunoblotting were applied to detect signaling pathways underlying the dose differential drug effects. The in vivo effects of single drug (CCI-779), and drug combination of CCI-779 with SL327 (a brain penetrant MEK inhibitor) to eliminate the unfavorable activation of MAPK pathway were evaluated in MDA-MB231-BR brain metastases xenograft mice. The two mTOR inhibitors, rapamycin and CCI-779, inhibited the invasion of brain metastatic cells only at a moderate concentration level, which was lost at higher concentrations secondary to activation of the MAPK signaling pathway. Pharmacological inhibition of ERK1/2 by PD98059 and SL327 restored the anti-invasion effects of mTOR inhibition in vitro. In vivo, a significant decrease was noted in the average number of micro and large metastatic lesions as well as the whole brain GFP expression in the CCI-779 1 mg/kg/day treated group compared with that in the vehicle group (P < 0.05). However, 10 mg/kg CCI-779 treatment did not show significant anti-metastasis effect on the animal model. High-dose CCI-779 eliciting the ERK MAPK activation in the brain metastatic lesion was corroborated. Combined with the brain penetrant MEK inhibitor SL327, high-dose CCI-779 significantly reduces the brain metastasis, and the combination treatment prohibited perivascular invasion of tumor cells and inhibits tumor angiogenesis in vivo. This study provides evidence on the potential value of CCI-779 as well as CCI-779 + SL327 in prohibiting breast cancer brain metastasis.

PMID: 21394501