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Cancer stem‑like cells (CSCs; also referred to as tumor‑initiating cells) play crucial roles in tumor progression and aggressiveness. Recent studies have demonstrated the antitumor activity of zoledronic acid (ZA), a third‑generation bisphosphonate, in various types of human cancer. However, its effect on oral CSCs and the underlying mechanism remain obscure. The present study demonstrated that ZA suppresses the growth and stemness properties of oral/oropharyngeal squamous cell carcinoma (OSCC) cells. ZA inhibited the malignant characteristics of OSCC cells, such as anchorage‑independent growth and epithelial thickening in organotypic raft cultures. Moreover, ZA treatment resulted in suppression of self‑renewal capacity, a key feature of CSCs. ZA also inhibited important CSC properties, such as migration and chemo‑radioresistance. Mechanistically, ZA exposure significantly decreased chemokine (C‑C motif) ligand 3 (CCL3) expression in OSCC cells. It was further demonstrated that CCL3 signaling via its receptor is crucial for supporting the CSC phenotype in OSCC cells. Moreover, an antagonist of the CCL3 receptor reversed the effect of CCL3 on CSC properties, and exogenous CCL3 rescued the suppressaed CSC phenotype in ZA‑treated OSCC cells. These results demonstrated that ZA suppresses the CSC phenotype in OSCC cells by reducing CCL3 expression, suggesting that ZA may be an effective therapeutic agent for oral cancer by targeting CSCs.

GV1001 is a 16‑amino acid peptide derived from the human telomerase reverse transcriptase (hTERT) protein (616‑626; EARPALLTSRLRFIPK), which lies within the reverse transcriptase domain. Originally developed as an anticancer vaccine, GV1001 demonstrates diverse cellular effects, including anti‑inflammatory, tumor suppressive and antiviral effects. In the present study, the radioprotective and antifibrotic effects of GV1001 were demonstrated through suppressing transforming growth factor‑β (TGF‑β) signaling. Proliferating human keratinocytes underwent premature senescence upon exposure to ionizing radiation (IR), however, treatment of cells with GV1001 allowed the cells to proliferate and showed a reduction in senescent phenotype. GV1001 treatment notably increased the levels of Grainyhead‑like 2 and phosphorylated (p‑)Akt (Ser473), and reduced the activation of p53 and the level of p21/WAF1 in irradiated keratinocytes. It also markedly suppressed the level of TGF‑β signaling molecules, including p‑small mothers against decapentaplegic (Smad)2/3 and Smad4, and TGF‑β target genes, including zinc finger E‑box binding homeobox 1, fibronectin, N‑cadharin and Snail, in irradiated keratinocytes. Furthermore, GV1001 suppressed TGF‑β signaling in primary human fibroblasts and inhibited myofibroblast differentiation. Chromatin immunoprecipitation revealed that GV1001 suppressed the binding of Smad2 on the promoter regions of collagen type III α1 chain (Col3a1) and Col1a1. In a dermal fibrosis model in vivo, GV1001 treatment notably reduced the thickness of fibrotic lesions and the synthesis of Col3a1. These data indicated that GV1001 ameliorated the IR‑induced senescence phenotype and tissue fibrosis by inhibiting TGF‑β signaling and may have therapeutic effects on radiation‑induced tissue damage.

Although efavirenz (EFV) is efficacious as an anti-retroviral therapy when combined with other antiretroviral drugs, it may cause adverse clinical effects, including skin and mucosal eruptions, central nervous system complications, hepatotoxicity, renal failure and pulmonary complications. The present study investigated the phenotypic alterations caused by EFV in normal human keratinocytes (NHKs) and determined the cell death pathways leading to the lack of epithelial proliferation and regeneration. Replication kinetics, cellular morphology, and protein and mRNA levels of cell cycle regulatory genes and cell death markers were compared between the EFV-exposed cells and the untreated control. EFV treatment led to cell proliferation arrest and cell death of the NHKs by inducing autophagy mediated by proteasome-dependent degradation of p53. EFV also reduced the levels of mTOR and active ERK signaling in NHKs. Chemical inhibition of p53 degradation with a proteasome inhibitor led to reduced autophagic response of NHKs to EFV. In addition, EFV triggered terminal differentiation of NHKs by inducing the expression of involucrin, filaggrin, loricrin and genes involved in cornified envelope formation. Inhibition of autophagy in the EFV-treated NHKs with 3-methylalanine reduced the levels of involucrin and the extent of cell death. Our data indicate that EFV elicits cytotoxic effects on NHKs in part through induction of autophagy and aberrant differentiation of cells.