American Association for Cancer Research
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Supplementary Table 1, Supplementary Figures 1-7, Supplementary Materials and Methods from MEK Inhibitor PD-0325901 Overcomes Resistance to PI3K/mTOR Inhibitor PF-5212384 and Potentiates Antitumor Effects in Human Head and Neck Squamous Cell Carcinoma

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journal contribution
posted on 2023-03-31, 18:23 authored by Suresh Mohan, Robert Vander Broek, Sujay Shah, Danielle F. Eytan, Matthew L. Pierce, Sophie G. Carlson, Jamie F. Coupar, Jialing Zhang, Hui Cheng, Zhong Chen, Carter Van Waes

Supplementary Table 1, Supplementary Figures 1-7, Supplementary Materials and Methods. Supplemental Table 1. Tumor, treatment, and outcome characteristics of human HNSCC lines Supplementary Figure 1. Boxplots of IC50s for 11 HPV- cell lines (red) and 8 HPV+ lines (cyan); Supplementary Figure 2. PF-384 effects on PI3K/mTOR, and MAPK/ERK pathways in UMSCC-46; Supplementary Figure 3 PF-384 effects on IKK-dependent phosphorylation of NF-κB p65 protein in UM-SCC-1 and 46; Supplementary Figure 4. Effects of PIK3CA knockdown on PI3K-AKT pathway and NF-κB signaling in UMSCC-1 and 46; Supplementary Figure 5. Effects of PF-384 and PD-901 treatment on weights of mice bearing UMSCC-1 xenografts; Supplementary Figure 6. Immunohistochemical staining of UMSCC-1 xenografts; Supplementary Figure 7. Schematic of PI3K/Akt/mTOR and MEK/ERK pathways and targets of PF-384 and PD-901



Purpose: Head and neck squamous cell carcinomas exhibit variable sensitivity to inhibitors of the PI3K/mTOR pathway, an important target of genomic alterations in this cancer type. The mitogen-activated protein kinase kinase (MEK)/ERK/activator protein 1 (AP-1) and nuclear factor-κB (NF-κB) pathways are also frequently co-activated, but their roles in resistance mechanisms to PI3K/mTOR inhibitors and as therapeutic targets in head and neck squamous cell carcinoma (HNSCC) are not well defined.Experimental Design: We determined the IC50s of dual PI3K/mTOR inhibitor PF-05212384 (PF-384) by XTT assays in 14 HNSCC lines with PI3K/Akt/mTOR cascade alterations. In two resistant models, we further characterized the molecular, cellular, and in vivo attributes and effects of combining PF-384 with MEK inhibitor PD-0325901 (PD-901).Results: PF-384 IC50s varied between 0.75 and 133 nmol/L in 14 HNSCC lines with overexpression or mutations of PIK3CA, and sensitivity correlated with increased phospho-AKT(T308/S473). In resistant UMSCC-1 and -46 models, PF-384 increased G0-/G1-phase accumulation but weakly induced sub-G0 cell death. PF-384 inhibited direct targets of PI3K/mTOR, but incompletely attenuated co-activated ERK and UMSCC-1 xenograft growth in vivo. PD-901 strongly inhibited MEK/ERK targets, and the combination of PF-384 and PD-901 inhibited downstream NF-κB and AP-1 transactivation, and IL8 and VEGF production in vitro. PD-901 potently inhibited tumor growth alone and with PF384, enhanced antiproliferative, apoptotic, and anti-angiogenesis activity in vivo.Conclusions: PI3K/mTOR inhibitor PF-384 exhibits variable activity in a panel of HNSCC cell lines with differing PIK3CA expression and mutation status. MEK inhibitor PD-901 overcomes resistance and enhances antitumor effects observed with PF-384 in vivo. Clin Cancer Res; 21(17); 3946–56. ©2015 AACR.