CD44 Mediates Oral Squamous Cell Carcinoma-Promoting Activity of MRE11 via AKT Signaling

Abstract

Oral cancer is one of the highest-incidence malignancies worldwide, with the occurrence of oral squamous cell carcinoma (OSCC) being the most frequently diagnosed form. A barrier for oral cancer management may arise from tumor cells that possess properties of cancer stemness, which has been recognized as a crucial factor in tumor recurrence and metastasis. As such, understanding the molecular mechanisms underlying these tumor cells may provide insights for improving cancer treatment. MRE11 is the core protein of the RAD50/MRE11/NBS1 complex with a primary role in DNA damage repair, and it has been diversely associated with tumor development including OSCC. In this study, we aimed to investigate the engagement of CD44, a cancer stemness marker functioning in the control of cell growth and motility, in OSCC malignancy under the influence of MRE11. We found that overexpression of MRE11 enhanced CD44 expression and tumorsphere formation in OSCC cells, whereas knockdown of MRE11 reduced these phenomena. In addition, the MRE11-promoted tumorsphere formation or cell migration ability was compromised in OSCC cells carrying siRNA that targets CD44, as was the MRE11-promoted AKT phosphorylation. These were further supported by analyzing clinical samples, where higher CD44 expression was associated with lymph node metastasis. Additionally, a positive correlation between the expression of MRE11 and CD44, or that of CD44 and phosphorylated AKT, was observed in OSCC tumor tissues. Finally, the expression of CD44 was found to be higher in the metastatic lung nodules from mice receiving tail vein-injection with MRE11-overexpressing OSCC cells compared with control mice, and a positive correlation between CD44 and phosphorylated AKT was also observed in these metastatic lung nodules. Altogether, our current study revealed a previously unidentified mechanism linking CD44 and AKT in MRE11-promoted OSCC malignancy, which may shed light to the development of novel therapeutic strategies in consideration of this new pathway in OSCC.

CD44 and its implication in neoplastic diseases

“…CD44 plays a role in various squamous cell carcinomas and has been shown to be mainly involved in EMT 128 and cancer stemness. 129 In HNSCC, HA binding to CD44 was found to increase CSCs numbers by PI3K–4EBP1–SOX2, whereas CD44 binding to VCAM‐1 contribute to invasiveness by ezrin/PI3K. Moreover, the switch from CD44v8–10 to CD44s was reported to promote EMT and participate in tumor invasion, 52 which is contrary to the results in ESCC of Yu et al.…”

“…CD44 plays a role in various squamous cell carcinomas and has been shown to be mainly involved in EMT 128 and cancer stemness 129 . In HNSCC, HA binding to CD44 was found to increase CSCs numbers by PI3K–4EBP1–SOX2, whereas CD44 binding to VCAM‐1 contribute to invasiveness by ezrin/PI3K.…”

“…CD44 plays a role in various squamous cell carcinomas and has been shown to be mainly involved in EMT 128 and cancer stemness. 129 In HNSCC, HA binding to CD44 was found to increase CSCs numbers by PI3K-4EBP1-SOX2, whereas CD44 binding to VCAM-1 contribute to invasiveness by ezrin/PI3K. Moreover, the switch from CD44v8-10 to CD44s was reported to promote EMT and participate in tumor invasion, 52 which is contrary to the results in ESCC of Yu et al 102 In mouse and human squamous cell carcinoma, it has been demonstrated that induction of a hybrid EMT state contributes to tumor initiation, progression, invasiveness, stemness, and metastasis by activating the CAMK2-CD44-SRC axis.…”

IL-1RA promotes oral squamous cell carcinoma malignancy through mitochondrial metabolism-mediated EGFR/JNK/SOX2 pathway

“…Formalin-fixed and paraffin-embedded normal and tumor tissue sections were immunostained using a Bond-Max automated IHC stainer (Leica Microsystems, Wetzlar, Germany) in accordance with the manufacturer’s instructions and our previous reports [ 24 , 27 ]. The following primary antibodies were used for IHC: goat anti-human IL-1RA (R&D Systems, Minneapolis, MN, USA), rabbit anti-human SOX2 (GeneTex, Hsinchu, Taiwan), rabbit anti-human Ki67 (GeneTex, Hsinchu, Taiwan), rabbit anti-human phospho-EGFR at Tyr1086 (GeneTex, Hsinchu, Taiwan), and rabbit anti-human phospho-JNK1/2/3 at Thr183/Thr183/Thr221 (Abcam, Waltham, MA, USA).…”

“…IHC images were captured using an Eclipse E600 microscope (Nikon, Tokyo, Japan), and total immunostaining scores for each tissue section were determined as the product of the percentage of positively stained cells (0, 0–4%; 1, 5–24%; 2, 25–49%; 3, 50–74%; 4, 75–100%) multiplied by the intensity of staining (0, negative; 1, weak; 2, moderate; 3, strong). To further analyze the association between IL-1RA expression and patient survival, the expression level of IL-1RA by IHC scoring was categorized into low versus high expression with cut-off values according to ROC curves [ 24 , 27 ].…”