Drug resistance occurred in a newly characterized preclinical model of lung cancer brain metastasis.

Abstract

Background Cancer metastasis and drug resistance have traditionally been studied separately, though these two lethal pathological phenomena almost always occur concurrently. Brain metastasis occurs in a large proportion of lung cancer patients (~30%). Once diagnosed, patients have a poor prognosis surviving typically less than 1 year due to lack of treatment efficacy. Methods Human metastatic lung cancer cells (PC-9-Br) were injected into the left cardiac ventricle of female athymic nude mice. Brain lesions were allowed to grow for 21 days, animals were then randomized into treatment groups and treated until presentation of neurological symptoms or when moribund. Prior to tissue collection mice were injected with Oregon Green and 14C-Aminoisobutyric acid followed by an indocyanine green vascular washout. Tracer accumulation was determined by quantitative fluorescent microscopy and quantitative autoradiography. Survival was tracked and tumor burden was monitored via bioluminescent imaging. Extent of mutation differences and acquired resistance was measured in-vitro through half-maximal inhibitory assays and qRT-PCR analysis. Results A PC-9 brain seeking line (PC-9-Br) was established. Mice inoculated with PC-9-Br resulted in a significantly decreased survival time compared with mice inoculated with parental PC-9. Non-targeted chemotherapy with cisplatin and etoposide (51.5 days) significantly prolonged survival of PC-9-Br brain metastases in mice compared to vehicle control (42 days) or cisplatin and pemetrexed (45 days). Further in-vivo imaging showed greater tumor vasculature in mice treated with cisplatin and etoposide compared to non-tumor regions, which was not observed in mice treated with vehicle or cisplatin and pemetrexed. More importantly, PC-9-Br showed significant resistance to gefitinib by in-vitro MTT assays (IC50>2.5 µM at 48hrs and 0.1 µM at 72hrs) compared with parental PC-9 (IC50: 0.75 µM at 48hrs and 0.027 µM at 72hrs). Further studies on the molecular mechanisms of gefitinib resistance revealed that EGFR and phospho-EGFR were significantly decreased in PC-9-Br compared with PC-9. Expression of E-cadherin and vimentin did not show EMT in PC-9-Br compared with parental PC-9, and PC-9-Br had neither T790 mutation nor amplifications of MET and HER2 compared with parental PC-9. Conclusion Our study demonstrated that brain metastases of lung cancer cells may independently prompt drug resistance without drug treatment.

Emodin enhances cisplatin sensitivity in non-small cell lung cancer through Pgp downregulation

“…Cisplatin is a common chemotherapy drug used in the treatment of various types of cancer; however, cisplatin also exhibits serious adverse effects, particularly nephrotoxicity and oxidative injury (23,31). Previous studies have reported that the therapeutic efficacy of emodin combined with chemical drugs is higher than that of chemical drugs alone, and that combination treatment also results in fewer adverse effects (7,15,32).…”