PLEK2 promotes cancer stemness and tumorigenesis of head and neck squamous cell carcinoma via the c‐Myc‐mediated positive feedback loop

Abstract

Background Head and neck squamous cell carcinoma (HNSCC) is one of the most frequent malignancies worldwide and is characterized by unfavorable prognosis, high lymph node metastasis and early recurrence. However, the molecular events regulating HNSCC tumorigenesis remain poorly understood. Therefore, uncovering the underlying mechanisms is urgently needed to identify novel and promising therapeutic targets for HNSCC. In this study, we aimed to explore the role of pleckstrin‐2 (PLEK2) in regulating HNSCC tumorigenesis. Methods The expression pattern of PLEK2 and its clinical significance in HNSCC were determined by analyzing publicly assessable datasets and our own independent HNSCC cohort. In vitro and in vivo experiments, including cell proliferation, colony formation, Matrigel invasion, tumor sphere formation, ALDEFLUOR, Western blotting assays and xenograft mouse models, were used to investigate the role of PLEK2 in regulating the malignant behaviors of HNSCC cells. The underlying molecular mechanisms for the tumor‐promoting role of PLEK2 were elucidated using co‐immunoprecipitation, cycloheximide chase analysis, ubiquitination assays, chromatin immunoprecipitation‐quantitative polymerase chain reaction, luciferase reporter assays and rescue experiments. Results The expression levels of PLEK2 mRNA and protein were significantly increased in HNSCC tissues, and PLEK2 overexpression was strongly associated with poor overall survival and therapeutic resistance. Additionally, PLEK2 was important for maintaining the proliferation, invasion, epithelial‐mesenchymal transition, cancer stemness and tumorigenesis of HNSCC cells and could alter the cellular metabolism of the cancer cells. Mechanistically, PLEK2 interacted with c‐Myc and reduced the association of F‐box and WD repeat domain containing 7 (FBXW7) with c‐Myc, thereby avoiding ubiquitination and subsequent proteasome‐mediated degradation of c‐Myc. Moreover, the c‐Myc signaling activated by PLEK2 was important for sustaining the aggressive malignant phenotypes and tumorigenesis of HNSCC cells. c‐Myc also directly bounded to the PLEK2 promoter and activated its transcription, forming a positive feedback loop. Conclusions Collectively, these findings uncover a previously unknown molecular basis of PLEK2‐enhanced c‐Myc signaling in HNSCC, suggesting that PLEK2 may represent a promising therapeutic target for treating HNSCC.

Targeting Squalene Epoxidase Confers Metabolic Vulnerability and Overcomes Chemoresistance in HNSCC

“…ChIP-qPCR: The ChIP assay was performed using the EZ ChIP Chromatin Immunoprecipitation Kit (Millipore, Billerica, MA, USA), following a previously described protocol. [45] Briefly, DNA-protein cross-links were generated by fixing the cell samples with 1% formaldehyde for 10 min at room temperature. After washing three times with PBS, the samples were lysed in RIPA buffer and then subjected to sonication to fragment the genomic DNA.…”

PLEK2 mediates metastasis and invasion via α5‐nAChR activation in nicotine‐induced lung adenocarcinoma

“…46,47 In addition, PLEK2 has also been shown to promote cancer cell stemness. 43 In this study, we found that the expression of α5-nAChR and PLEK2 was significantly Furthermore, we found a skeleton protein molecule, CFL1, with a high correlation with PLEK2 via UALCAN online analysis and in vitro and in vivo experiments in LUAD. CFL belongs to the ADF/CFL family, which contains two subtypes, CFL1 and CFL2.…”

“…In recent years, the biological function of PLEK2 in tumors has been widely studied. It has been shown to play a role in promoting the occurrence and development of lung cancer, gallbladder cancer, gastric cancer and other tumors 42–44 . In lung cancer, PLEK2 can directly interact with SHIP2 and degrade SHIP2 through phosphorylation‐mediated ubiquitination, while SHIP2 can negatively regulate the PI3K/AKT pathway by dephosphorylating PIP3 to PIP2 to restrict cancer progression 29,45 .…”

Pleckstrin‐2‐promoted PPM1B degradation plays an important role in transforming growth factor‐β‐induced breast cancer cell invasion and metastasis

“…14,15 Moreover, PLEK2 interacts with c-Myc to prevent its proteasomemediated degradation in head and neck squamous cell carcinoma. 43 Here, we determined that PLEK2 interacted with PPM1B in breast cancer cells (Figure 8A These results suggest that the PLEK2-PPM1B axis exerts prometastatic functions through the NF-κB signaling pathway.…”

“…Additionally, PLEK2 interacts with SHIP2 in non‐small‐cell lung cancer cells to target this protein for degradation, which leads to activation of the PI3K/Akt signaling pathway 14,15 . Moreover, PLEK2 interacts with c‐Myc to prevent its proteasome‐mediated degradation in head and neck squamous cell carcinoma 43 . Here, we determined that PLEK2 interacted with PPM1B in breast cancer cells (Figure 8A,C,D).…”