Preclinical study of PD-0332991 on EBV-positive NPC cell lines and xenografts.

Abstract

e17506 Background: Originated from nasopharynx, nasopharyngeal carcinoma is a subtype of head and neck cancer, which is consistently associated with EBV infection. It is prevalent exclusively in south of China, Malaysia and southeast Asia. Previously, there was only one EBV positive cell line, c666-1, for NPC study, the new EBV positive cell lines and xenografts established by our lab recently represent better models for preclinical drug test. The objective of this preclinical study is to evaluate the therapeutic effect of specific CDK4/6 inhibitor PD-0332991 in our new established EBV positive NPC cell lines and Xenografts. Methods: Cell lines were cultured in both 2D and 3D condition, cytotoxic test was conduct by Resazurin in 2D and by cell titer-glo in 3D. Cell cycle was analyzed by Western blot and flow cytometry. In the animal study, PD-0332991 was first used as single drug administrated to xenograft mice daily by oral gavage. Secondly, SAHA as a HDAC inhibitor was used to combine with PD-0332991 in this study, which was i.p. injected into animal every other day. Tumor size, body weight well as micro-pets scan data was recorded. The data from each experiment was analyzed by ANOVA and unpaired t-test for significant drug responses. Results: PD-0332991 was first identified to be effective during in vitro study. Beside single drug effect, when combination with SAHA, a synergistic effect was observed both in vitro and in vivo. In single drug study, PD-0332991 can significantly inhibit tumor growth in 3 of our xenografts (XENO76: P < 0.0001, XENO32: P < 0.0001, XENO23: P = 0.0019). In combination study, through tumor size and micro-pets scan, combination treatment induced significant decrease in tumor size and tumor metabolism states in animal models compare to vehicle, PD-0332991 and SAHA treatment. Conclusions: PD-0332991 is identified to be effective in our preclinical test by using our new established EBV positive cell lines and xenografts, this could be a promising treatment for NPC patients after clinical trial.