Chemical Oral Cancerogenesis Is Impaired in PI3Kγ Knockout and Kinase-Dead Mice

Abstract

We investigated the role of PI3Kγ in oral carcinogenesis by using a murine model of oral squamous carcinoma generated by exposure to 4-nitroquinoline 1-oxide (4NQO) and the continuous human cancer cell line HSC-2 and Cal-27. PI3Kγ knockout (not expressing PI3Kγ), PI3Kγ kinase-dead (carrying a mutation in the PI3Kγ gene causing loss of kinase activity) and wild-type (WT) C57Bl/6 mice were administered 4NQO via drinking water to induce oral carcinomas. At sacrifice, lesions were histologically examined and stained for prognostic tumoral markers (EGFR, Neu, cKit, Ki67) and inflammatory infiltrate (CD3, CD4, CD8, CD19 and CD68). Prevalence and incidence of preneoplastic and exophytic lesions were significantly and similarly delayed in both transgenic mice versus the control. The expression of prognostic markers, as well as CD19+ and CD68+ cells, was higher in WT, while T lymphocytes were more abundant in tongues isolated from transgenic mice. HSC-2 and Cal-27 cells were cultured in the presence of the specific PI3Kγ-inhibitor (IPI-549) which significantly impaired cell vitality in a dose-dependent manner, as shown by the MTT test. Here, we highlighted two different mechanisms, namely the modulation of the tumor-infiltrating cells and the direct inhibition of cancer-cell proliferation, which might impair oral cancerogenesis in the absence/inhibition of PI3Kγ.

Polymorphonuclear myeloid-derived suppressor cells and phosphatidylinositol-3 kinase gamma are critical to tobacco-mimicking oral carcinogenesis in mice

“…41 42 Our data using a pharmacological inhibitor of PI3Kγ are consistent with a recent report that observed reduced rates of preneoplastic lesions and SCCs induced by 4NQO in the tongues of genetically engineered mice lacking PI3Kγ or expressing a kinase-dead PI3Kγ compared with wild-type C57Bl/6 mice. 43 In addition to reducing progression of dysplasia and preventing tumorigenesis, we also demonstrated that inhibition of PI3Kγ reduces Ly6G+ cell recruitment to sites of dysplasia and that these leukocytes play a critical role in establishing invasive SCC. While studies using PI3Kγ inhibitors have acknowledged an influence on PMN-MDSCs, these studies largely focus on tumor-associated macrophage polarization and activity or a more general effect on tumorassociated myeloid cells broadly.…”

Cystatin SN (CST1) as a Novel Salivary Biomarker of Periodontitis

“…Total proteins from each saliva sample (30 µg) were separated by SDS-PAGE as previously reported [ 56 ]. Gels were transferred to membranes, saturated with blocking solution (5% milk and 0.1% Tween-20 in PBS), and incubated with anti-CST1 primary antibody (1:500; Santa Cruz Biotechnology Inc., Dallas, TX, USA) overnight at 4 °C.…”

“…Total proteins from each saliva sample (30 µg) were separated by SDS-PAGE as previously reported [56]. Gels were transferred to membranes, saturated with blocking solution (5% milk and 0.1% Tween-20 in PBS), and incubated with anti-CST1 primary antibody (1:500; Santa Cruz Biotechnology Inc., Dallas, TX, USA) overnight at 4 • C. Membranes were then rinsed three times and incubated with the appropriate concentration of secondary antibody conjugated with horseradish peroxidase for 1 h at room temperature.…”

Metformin Protects Rat Skeletal Muscle from Physical Exercise-Induced Injury

“…The sections were dehydrated with ascending ethanol passages and mounted in dibutylphthalate polystyrene xylene (DPX), (BDH) [ 28 ].…”