The oncogenicity of tumor-derived mutant p53 is enhanced by the recruitment of PLK3.

p53 mutations with single amino acid changes in cancer often lead to dominant oncogenic changes. Here, we have developed a mouse model of gain-of-function (GOF) p53-driven lung cancer utilizing conditionally active LSL p53-R172H and LSL K-Ras-G12D knock-in alleles that can be activated by Cre in lung club cells. Mutation of the p53 transactivation domain (TAD) (p53-L25Q/W26S/R172H) eliminating significant transactivation activity resulted in loss of tumorigenicity, demonstrating that transactivation mediated by or dependent on TAD is required for oncogenicity by GOF p53. GOF p53 TAD mutations significantly reduce phosphorylation of nearby p53 serine 20 (S20), which is a target for PLK3 phosphorylation. Knocking out PLK3 attenuated S20 phosphorylation along with transactivation and oncogenicity by GOF p53, indicating that GOF p53 exploits PLK3 to trigger its transactivation capability and exert oncogenic functions. Our data show a mechanistic involvement of PLK3 in mutant p53 pathway of oncogenesis.

Autophagy blockade sensitizes human head and neck squamous cell carcinoma towards CYT997 through enhancing excessively high reactive oxygen species-induced apoptosis.

The functional relationship between apoptosis and autophagy in anticancer drug treatment is extremely complex, and the molecular machinery is obscure. This study aims to investigate the efficacy of CYT997, a novel microtubule-disrupting agent, in head and neck squamous cell carcinomas (HNSCCs) and complete the autophagy-apoptosis puzzle involved in drug action. We report here that CYT997 exhibits anticancer activity by triggering oxidative stress-associated apoptosis in HNSCC cells. Interestingly, upregulation of autophagy by mTOR-dependent pathways appears to have a cytoprotective role in preventing apoptosis by inhibiting CYT997-induced excessively high levels of reactive oxygen species (ROS). Blockade of autophagy by ATG7 depletion or addition of autophagy inhibitor hydroxychloroquine (HCQ) sensitizes HNSCC cells to CYT997 as evidenced by enhanced ROS-associated apoptosis. Moreover, HCQ exhibits a good synergism with CYT997 on induction of apoptosis in HNSCC xenografts without cytotoxicity, suggesting combined treatment of CYT997 with autophagy inhibitors would increase the anticancer efficacy of CYT997. These findings unveil the importance of ROS in crosstalk between autophagy and apoptosis in CYT997 treatment, raising concerns that genetic or pharmacologic blockade of autophagy should be considered in the design of new therapeutics for HNSCC. KEY MESSAGES: • CYT997 exhibits anticancer activity by induction of ROS-associated apoptosis. • mTOR-dependent cytoprotective autophagy prevents CYT997-induced apoptosis. • Blockade of autophagy augments CYT997 efficacy by enhanced ROS-associated apoptosis. • Combination of autophagy inhibitors with CYT997 is more effective against HNSCC.

Fabrication, characterization, and in vitro evaluation of silver-containing arabinoxylan foams as antimicrobial wound dressing.

Arabinoxylan ferulate (AXF) foams were fabricated via enzymatic peroxidase/hydrogen peroxide crosslinking reaction followed by freeze-drying and studied as a potential wound dressing material. The AXF foam's rheological, morphological, porous, and swelling properties were examined. AXF foams were found to be a viscoelastic material that proved to be highly porous and water absorbent. AXF foams possessed low endotoxin levels and were cytocompatible with fibroblasts. Silver was successfully integrated into AXF foams and slowly released over 48 h. AXF foams impregnated with silver demonstrated efficacy inhibiting bacterial growth according to a modified Kirby-Bauer disk diffusion susceptibility test. Overall, AXF foams possess appropriate material properties and the silver-loaded AXF foams showed antimicrobial activity necessary to be a candidate material in wound dressing development. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2456-2465, 2016.

p53 mutants induce transcription of NF-κB2 in H1299 cells through CBP and STAT binding on the NF-κB2 promoter and gain of function activity.

Cancer cells with p53 mutations, in general, grow more aggressively than those with wild-type p53 and show "gain of function" (GOF) phenotypes such as increased growth rate, enhanced resistance to chemotherapeutic drugs, increased cell motility and tumorigenicity; although the mechanism for this function remains unknown. In this communication we report that p53-mediated NF-κB2 up-regulation significantly contributes to the aggressive oncogenic behavior of cancer cells. Lowering the level of mutant p53 in a number of cancer cell lines resulted in a loss of GOF phenotypes directly implicating p53 mutants in the process. RNAi against NF-κB2 in naturally occurring cancer cell lines also lowers GOF activities. In H1299 cells expressing mutant p53, chromatin immunoprecipitation (ChIP) assays indicate that mutant p53 induces histone acetylation at specific sites on the regulatory regions of its target genes. ChIP assays using antibodies against transcription factors putatively capable of interacting with the NF-κB2 promoter show increased interaction of CBP and STAT2 in the presence of mutant p53. Thus, we propose that in H1299 cells, mutant p53 elevates expression of genes capable of enhancing cell proliferation, motility, and tumorigenicity by inducing acetylation of histones via recruitment of CBP and STAT2 on the promoters causing CBP-mediated histone acetylation.