Inhibition of Bruton’s tyrosine kinase as a therapeutic strategy for chemoresistant oral squamous cell carcinoma and potential suppression of cancer stemness

Abstract

Locally advanced oral squamous cell carcinoma (OSCC) requires multimodal therapy, including surgery and concurrent chemoradiotherapy (CCRT). CCRT-resistant and recurrent cancer has a poor prognosis. We investigated the effects of Bruton’s tyrosine kinase (BTK) on CCRT-resistant OSCC tissues. The effect of ibrutinib, a first-in-class BTK inhibitor, was tested on stem cell-like OSCC tumorspheres. A tissue array was constructed using tissue samples from 70 patients with OSCC. Human OSCC cell lines, SAS, TW2.6 and HSC-3, were examined. Wound healing, Matrigel invasion, and tumorsphere formation assays, as well as immunofluorescence analysis and flow cytometry, were used to investigate the effects of BTK knockdown (shBTK), ibrutinib, cisplatin, and ibrutinib/cisplatin combination on OSCC cells. We demonstrated that BTK was aberrantly highly expressed in the clinical CCRT-resistant OSCC tissue array, which resulted in poor overall survival in our local Tri-Service General Hospital and freely accessible TCGA OSCC cohorts. shBTK significantly downregulated the stemness markers Nanog, CD133, T cell immunoglobulin-3 (TIM-3), and Krüppel-like factor 4 (KLF4) in SAS tumorspheres and attenuated OSCC cell migration and colony formation. Ibrutinib reduced the number of aldehyde dehydrogenase (ALDH)-rich OSCC cells and reduced tumorsphere formation, migration, and invasion in a dose-dependent manner. Compared with ibrutinib or cisplatin monotherapy, the ibrutinib/cisplatin combination significantly reduced the formation of ALDH + OSCC tumorspheres and enhanced apoptosis. These results demonstrate that ibrutinib effectively inhibits the CSCs-like phenotype of OSCC cells through dysregulation of BTK/CD133 signaling. The ibrutinib/cisplatin combination may be considered for future clinical use.

Prognostic And Immunological Implications of BTK Expression In Pan-Cancer

“…We studied the expression of BTK in pan-cancer and adjacent tissues or normal tissues in data from 33 cancer types from TCGA database. We observed elevated expression of BTK in BRCA [49], CHOL, GBM [50], HNSC [51], KICH, KIRC [52] and KIRP, while lower expression was observed in BLCA, COAD, LUAD, LUSC, PAAD and READ. We also found that BTK expression was associated with the clinical stage of 10 types of cancers, including ACC, BLCA, ESCA, KICH, KIRP, LUAD, SKCM, STAD, TGCT and THCA.…”

The Molecular Basis and Therapeutic Aspects of Cisplatin Resistance in Oral Squamous Cell Carcinoma

“…The combination of PI3K inhibitor, BKM-120, with TPF decreased the expression and phosphorylation of stathmin, and induced cell cycle arrest, thereby increasing the proportion of apoptotic tumor cells and inhibiting the growth of xenografts (169). The combination of Bruton's tyrosine kinase (BTK) inhibitors, ibrutinib, and cisplatin were capable of suppressing stemness characteristics and promoting apoptosis in OSCC cells (170).…”

Clinical Trials of the BTK Inhibitors Ibrutinib and Acalabrutinib in Human Diseases Beyond B Cell Malignancies

“…These include both direct tumoricidal activities on cancer cells and indirect immunomodulatory effects on different immune cell subsets as well as other relevant cell types in the tumor microenvironment (TME) via on-target inhibition of BTK (for both drugs) or off-target inhibition of ITK or EGFR (for ibrutinib) (2, 24, 28, 29). Ibrutinib and acalabrutinib exhibit direct tumoricidal activities on certain types of solid tumor cells, including neuroblastoma, glioblastoma, breast cancer, prostate cancer, bladder cancer and advanced oral squamous cell carcinoma (OSCC) (30,31,78,(80)(81)(82). Accumulating studies report that BTK is highly expressed in certain solid tumor cells and increased BTK levels are associated with a poor prognosis in patients (30,31,78,(80)(81)(82).…”

“…Ibrutinib and acalabrutinib exhibit direct tumoricidal activities on certain types of solid tumor cells, including neuroblastoma, glioblastoma, breast cancer, prostate cancer, bladder cancer and advanced oral squamous cell carcinoma (OSCC) (30,31,78,(80)(81)(82). Accumulating studies report that BTK is highly expressed in certain solid tumor cells and increased BTK levels are associated with a poor prognosis in patients (30,31,78,(80)(81)(82). Gene silencing of BTK or inhibition of BTK with ibrutinib or acalabrutinib attenuates the proliferation, migration, invasion and stemness of these cancer cells both in vitro and in vivo (30,31,78,(80)(81)(82).…”

“…Accumulating studies report that BTK is highly expressed in certain solid tumor cells and increased BTK levels are associated with a poor prognosis in patients (30,31,78,(80)(81)(82). Gene silencing of BTK or inhibition of BTK with ibrutinib or acalabrutinib attenuates the proliferation, migration, invasion and stemness of these cancer cells both in vitro and in vivo (30,31,78,(80)(81)(82). Mechanistically, ibrutinib or acalabrutinib potently inhibits BTK phosphorylation and its downstream oncogenic pathways such as the PI3K-mTOR and MEK/MAPK pathways, resulting in impaired tumorigenicity of these tumor cells (30,31,78,(80)(81)(82).…”