Lapatinib distribution in HER2 overexpressing experimental brain metastases of breast cancer.

PURPOSE: Lapatinib, a small molecule EGFR/HER2 inhibitor, partially inhibits the outgrowth of HER2+ brain metastases in preclinical models and in a subset of CNS lesions in clinical trials of HER2+ breast cancer. We investigated the ability of lapatinib to reach therapeutic concentrations in the CNS following (14)C-lapatinib administration (100 mg/kg p.o. or 10 mg/kg, i.v.) to mice with MDA-MD-231-BR-HER2 brain metastases of breast cancer. METHODS: Drug concentrations were determined at differing times after administration by quantitative autoradiography and chromatography. RESULTS: (14)C-Lapatinib concentration varied among brain metastases and correlated with altered blood-tumor barrier permeability. On average, brain metastasis concentration was 7-9-fold greater than surrounding brain tissue at 2 and 12 h after oral administration. However, average lapatinib concentration in brain metastases was still only 10-20% of those in peripheral metastases. Only in a subset of brain lesions (17%) did lapatinib concentration approach that of systemic metastases. No evidence was found of lapatinib resistance in tumor cells cultured ex vivo from treated brains. CONCLUSIONS: Results show that lapatinib distribution to brain metastases of breast cancer is partially restricted and blood-tumor barrier permeability is a key component of lapatinib therapeutic efficacy which varies between tumors.

Uptake of ANG1005, a novel paclitaxel derivative, through the blood-brain barrier into brain and experimental brain metastases of breast cancer.

PURPOSE: We evaluated the uptake of angiopep-2 paclitaxel conjugate, ANG1005, into brain and brain metastases of breast cancer in rodents. Most anticancer drugs show poor delivery to brain tumors due to limited transport across the blood-brain barrier (BBB). To overcome this, a 19-amino acid peptide (angiopep-2) was developed that binds to low density lipoprotein receptor-related protein (LRP) receptors at the BBB and has the potential to deliver drugs to brain by receptor-mediated transport. METHODS: The transfer coefficient (K(in)) for brain influx was measured by in situ rat brain perfusion. Drug distribution was determined at 30 min after i.v. injection in mice bearing intracerebral MDA-MB-231BR metastases of breast cancer. RESULTS: The BBB K(in) for (125)I-ANG1005 uptake (7.3 +/- 0.2 x 10(-3) mL/s/g) exceeded that for (3)H-paclitaxel (8.5 +/- 0.5 x 10(-5)) by 86-fold. Over 70% of (125)I-ANG1005 tracer stayed in brain after capillary depletion or vascular washout. Brain (125)I-ANG1005 uptake was reduced by unlabeled angiopep-2 vector and by LRP ligands, consistent with receptor transport. In vivo uptake of (125)I-ANG1005 into vascularly corrected brain and brain metastases exceeded that of (14)C-paclitaxel by 4-54-fold. CONCLUSIONS: The results demonstrate that ANG1005 shows significantly improved delivery to brain and brain metastases of breast cancer compared to free paclitaxel.

Heterogeneous blood-tumor barrier permeability determines drug efficacy in experimental brain metastases of breast cancer.

PURPOSE: Brain metastases of breast cancer appear to be increasing in incidence, confer significant morbidity, and threaten to compromise gains made in systemic chemotherapy. The blood-tumor barrier (BTB) is compromised in many brain metastases; however, the extent to which this influences chemotherapeutic delivery and efficacy is unknown. Herein, we answer this question by measuring BTB passive integrity, chemotherapeutic drug uptake, and anticancer efficacy in vivo in two breast cancer models that metastasize preferentially to brain. EXPERIMENTAL DESIGN: Experimental brain metastasis drug uptake and BTB permeability were simultaneously measured using novel fluorescent and phosphorescent imaging techniques in immune-compromised mice. Drug-induced apoptosis and vascular characteristics were assessed using immunofluorescent microscopy. RESULTS: Analysis of over 2,000 brain metastases from two models (human 231-BR-Her2 and murine 4T1-BR5) showed partial BTB permeability compromise in greater than 89% of lesions, varying in magnitude within and between metastases. Brain metastasis uptake of ¹4C-paclitaxel and ¹4C-doxorubicin was generally greater than normal brain but less than 15% of that of other tissues or peripheral metastases, and only reached cytotoxic concentrations in a small subset (∼10%) of the most permeable metastases. Neither drug significantly decreased the experimental brain metastatic ability of 231-BR-Her2 tumor cells. BTB permeability was associated with vascular remodeling and correlated with overexpression of the pericyte protein desmin. CONCLUSIONS: This work shows that the BTB remains a significant impediment to standard chemotherapeutic delivery and efficacy in experimental brain metastases of breast cancer. New brain permeable drugs will be needed. Evidence is presented for vascular remodeling in BTB permeability alterations.

Vorinostat inhibits brain metastatic colonization in a model of triple-negative breast cancer and induces DNA double-strand breaks.

PURPOSE: As chemotherapy and molecular therapy improve the systemic survival of breast cancer patients, the incidence of brain metastases increases. Few therapeutic strategies exist for the treatment of brain metastases because the blood-brain barrier severely limits drug access. We report the pharmacokinetic, efficacy, and mechanism of action studies for the histone deactylase inhibitor vorinostat (suberoylanilide hydroxamic acid) in a preclinical model of brain metastasis of triple-negative breast cancer. EXPERIMENTAL DESIGN: The 231-BR brain trophic subline of the MDA-MB-231 human breast cancer cell line was injected into immunocompromised mice for pharmacokinetic and metastasis studies. Pharmacodynamic studies compared histone acetylation, apoptosis, proliferation, and DNA damage in vitro and in vivo. RESULTS: Following systemic administration, uptake of [(14)C]vorinostat was significant into normal rodent brain and accumulation was up to 3-fold higher in a proportion of metastases formed by 231-BR cells. Vorinostat prevented the development of 231-BR micrometastases by 28% (P = 0.017) and large metastases by 62% (P < 0.0001) compared with vehicle-treated mice when treatment was initiated on day 3 post-injection. The inhibitory activity of vorinostat as a single agent was linked to a novel function in vivo: induction of DNA double-strand breaks associated with the down-regulation of the DNA repair gene Rad52. CONCLUSIONS: We report the first preclinical data for the prevention of brain metastasis of triple-negative breast cancer. Vorinostat is brain permeable and can prevent the formation of brain metastases by 62%. Its mechanism of action involves the induction of DNA double-strand breaks, suggesting rational combinations with DNA active drugs or radiation.