Chronopharmacodynamics and mechanisms of antitumor effect induced by erlotinib in xenograft-bearing nude mice.

Receptor tyrosine kinases, mediators of a variety of critical cellular functions, contribute to tumor progression and metastasis. The epidermal growth factor receptor (EGFR), a member of the receptor tyrosine kinase family, is ubiquitously expressed on the surface of mammalian cells. Erlotinib hydrochloride (Tarceva) can inhibit the intracellular phosphorylation of tyrosine kinases. To investigate the influence of dosing time on the ability of erlotinib to inhibit tumor growth and the underlying molecular mechanisms via the PI3K/AKT and ERK/MAPK pathway, we established nude mice HCC827 tumor xenografts models. The tumor-bearing mice were housed 3-4 per cage under standardized light/dark cycle conditions (lights on at 07:00 h, off at 19:00 h) with food and water ad libitum. The mice were randomly divided into erlotinib treated groups and control groups, gavaged with erlotinib and vehicle respectively at 6 different time points for 21 days. To draw tumor growth curves, the tumor volume was measured every three days. After the mice were sacrificed, the tumor masses of each group were removed and weighed. The relative protein expression levels of p-EGFR, p-AKT and p-MAPK were assayed at 4 h after erlotinib or vehicle gavage by Western blot analysis. The antitumor effect of erlotinib presented diurnal rhythmicity. The growth of HCC827 xenograft was more potently inhibited by erlotinib in the early light phase than in the early dark phase (p < 0.05). The inhibitory effect of erlotinib on phosphorylation of EGFR, AKT and MAPK varied with its administration time. The results indicate that the antitumor effect of erlotinib is more potent when the drug was administered when the activities of EGFR and its downstream factors increased. Our findings may provide a clue to optimize the dosing schedule of erlotinib.

Curcumin inhibits the proliferation and invasion of human osteosarcoma cell line MG-63 by regulating miR-138.

OBJECTIVE: In this study, we screened the different human osteosarcoma cell line MG-63 miRNAs after the treatment of curcumin and explored the effects of curcumin on MG-63 cells and its mechanism. METHODS: Affemitrix miRNA chip was used to detect the changes of miRNA expression profile in MG-63 cells before and after curcumin treatment, and screen different expression of miRNAs. The target gene of miRNA was analyzed by bioinformatics. The expression levels of miRNA-138 target genes Smad4, NFκB p65 and cyclin D3 were detected. MTT and Transwell Cell invasion assays were used to observe the effects of curcumin on MG-63 cells. RESULTS: Curcumin could significantly inhibit the proliferation of MG-63 cells and the expression levels of miRNA-138 target genes Smad4, NFκB p65 and cyclin D3 in MG-63 cells (P<0.05); overexpression of hsa-miR-138 down-regulated the expression levels of Smad4, NFκB p65 and cyclin D3 compared with the treatment of curcumin, while inhibition of hsa-miR-138 up-regulated the expression levels of Smad4, NFκB p65 and cyclin D3. CONCLUSIONS: Curcumin could increase the expression of hsa-miR-138, hsa-miR-138 inhibited cell proliferation and invasive ability by inhibition of its target genes.

Chronopharmacology and mechanism of antitumor effect of erlotinib in Lewis tumor-bearing mice.

The epidermal growth factor receptor (EGFR), a ubiquitously expressed receptor tyrosine kinase, is recognized as a key mediator of tumorigenesis in many human epithelial tumors. Erlotinib is tyrosine kinase inhibitor approved by FDA for use in oncology. It inhibits the intracellular phosphorylation of tyrosine kinase associated with the EGFR to restrain the development of the tumor. To investigate the antitumor effect of erlotinib at different dosing times and the underlying molecular mechanism via the PI3K/AKT pathway, we established a mouse model of Lewis lung cancer xenografts. The tumor-bearing mice were housed four or five per cage under standardized light-dark cycle conditions (light on at 7:00 AM, 500 Lux, off at 7:00 PM, 0 Lux) with food and water provided ad libitum. The mice were observed for quality of life, their body weight and tumor volume measured, and the tumor growth curves drawn. After being bled, the mice were sacrificed by cervical dislocation. The tumor masses were removed at different time points and weighed. The mRNA expression of EGFR, AKT, Cyclin D1 and CDK-4 were assayed by quantitative real-time PCR (qRT-PCR). Protein expression levels of AKT, P-AKT and Cyclin D1 were determined by Western blot analysis. The results suggest that erlotinib has a significant antitumor effect on xenografts of non-small cell lung cancer in mice, and its efficacy and toxicity is dependent on the time of day of administration. Its molecular mechanism of action might be related to the EGFR-AKT-Cyclin D1-CDK-4 pathway which plays a crucial role in the development of pathology. Therefore, our findings suggest that the time of day of administration of Erlotinib may be a clinically important variable.