The MASTL-ENSA-PP2A/B55 axis modulates cisplatin resistance in oral squamous cell carcinoma

TIPRL1 and its ATM-dependent phosphorylation promote radiotherapy resistance in head and neck cancer

PURPOSE

TIPRL1 (target of rapamycin signaling pathway regulator-like 1) is a known interactor and inhibitor of protein phosphatases PP2A, PP4 and PP6 - all pleiotropic modulators of the DNA Damage Response (DDR). Here, we investigated the role of TIPRL1 in the radiotherapy (RT) response of Head and Neck Squamous Cell Carcinoma (HNSCC).

METHODS

TIPRL1 mRNA (cBioportal) and protein expression (immunohistochemistry) in HNSCC samples were linked with clinical patient data. TIPRL1-depleted HNSCC cells were generated by CRISPR/Cas9 editing, and effects on colony growth, micronuclei formation (microscopy), cell cycle (flow cytometry), DDR signaling (immunoblots) and proteome (mass spectrometry) following RT were assessed. Mass spectrometry was used for TIPRL1 phosphorylation and interactomics analysis in irradiated cells.

RESULTS

TIPRL1 expression was increased in tumor versus non-tumor tissue, with high tumoral TIPRL1 expression associating with lower locoregional control and decreased survival of RT-treated patients. TIPRL1 deletion in HNSCC cells resulted in increased RT sensitivity, a faster but prolonged cell cycle arrest, increased micronuclei formation and an altered proteome-wide DDR. Upon irradiation, ATM phosphorylates TIPRL1 at Ser265. A non-phospho Ser265Ala mutant could not rescue the increased radiosensitivity phenotype of TIPRL1-depleted cells. While binding to PP2A-like phosphatases was confirmed, DNA-dependent protein kinase (DNA-PKcs), RAD51 recombinase and nucleosomal histones were identified as novel TIPRL1 interactors. Histone binding, although stimulated by RT, was adversely affected by TIPRL1 Ser265 phosphorylation.

CONCLUSIONS

Our findings underscore a clinically relevant role for TIPRL1 and its ATM-dependent phosphorylation in RT resistance through modulation of the DDR, highlighting its potential as a new HNSCC predictive marker and therapeutic target.

Fisetin, a dietary flavonoid, increases the sensitivity of chemoresistant head and neck carcinoma cells to cisplatin possibly through HSP90AA1/IL-17 pathway

Cisplatin (DDP) resistance is a bottleneck in the treatment of head and neck cancer (HNC), leading to poor prognosis. Fisetin, a dietary flavonoid, has low toxicity and high antitumor activity with unclear mechanisms. We intended to predict the targets of fisetin for reversing DDP-resistance and further verify their expressions and roles. A network pharmacology approach was applied to explore the target genes. The hub genes were screened out and subjected to molecular docking and experimental verification (in vivo and in vitro). Thirty-two genes common to fisetin and DDP-resistance were screened, including three hub genes, namely HSP90AA1, PPIA, and PTPRS. Molecular docking suggested that fisetin and the candidate proteins could bind tightly. HSP90AA1 was identified as the key gene. Administration of fisetin increased the sensitivity of chemoresistant cells (Cal27/DDP and FaDu/DDP) to DDP, accompanied by the downregulation of HSP90AA1 and IL-17. HSP90AA1 silencing increases the sensitivity of DDP-resistant cells to DDP, which was mediated by IL-17. In summary, fisetin might inhibit the chemoresistance of HNC cells to DDP by targeting the HSP90AA1/IL-17 pathway. Several hub genes might be the targets of fisetin for reversing DDP-resistance in HNC cells and might also serve as prognostic factors and therapeutic targets for HNC.

Role of the PP2A Pathway in Cholangiocarcinoma: State of the Art and Future Perspectives

Cholangiocarcinoma represents a heterogeneous disease at both a clinical and molecular level [...].