Yang Chen

Cancer stem cells (CSCs) contribute to chemotherapy resistance and poor prognosis, posing significant challenges in the treatment of oral squamous cell carcinoma. The extracellular matrix (ECM)-constructed microenvironment remodels the niche of CSCs. Yet mechanisms by which biophysical properties of ECM relate to CSCs remain undefined. Here, our findings link ECM mechanical stimuli to CSCs phenotype transition, and propose that ECM stiffening mechanoactivates tumor cells to dedifferentiate and acquire CD44⁺ stem cell-like characteristics through noncanonical mechanotransduction. ITGB1 senses and transduces biomechanical signals, while FERMT1 acts as an intracellular mechanotransduction downstream, activating CSCs. Mechanistically, FERMT1 promotes the proteasomal degradation of CK1α by E3 ubiquitin ligase MIB1, thereby triggering Wnt signaling pathway. Combining targeted ECM softening with mechanotransduction inhibition strategy significantly attenuates tumor stemness and chemoresistance in vivo. Therefore, our findings highlight the role of ECM in regulating CSCs via biomechanical-dependent manner, suggesting the ECM/ITGB1/FERMT1/Wnt axis as a promising therapeutic target for CSCs therapy.

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A decline in mucosal vascularity is a histological hallmark of oral submucous fibrosis (OSF), a premalignant disease that is largely induced by betel quid chewing. However, the lack of available models has challenged studies of angiogenesis in OSF. Here, we found that the expression of thrombospondin 1 (THBS1), an endogenous angiostatic protein, was elevated in the stroma of tissues with OSF. Using a fibroblast-attached organoid (FAO) model, the overexpression of THBS1 in OSF was stably recapitulated in vitro. In the FAO model, treatment with arecoline, a major pathogenic component in areca nuts, enhanced the secretion of transforming growth factor (TGF)-β1 by epithelial cells, which then promoted the expression of THBS1 in fibroblasts. Furthermore, human umbilical vein endothelial cells (HUVECs) were incorporated into the FAO to mimic the vascularized component. Overexpression of THBS1 in fibroblasts drastically suppressed the sprouting ability of endothelial cells in vascularized FAOs (vFAOs). Consistently, treatment with arecoline reduced the expression of CD31 in vFAOs, and this effect was attenuated when the endothelial cells were preincubated with neutralizing antibody of CD36, a receptor of THBS1. Finally, in an arecoline-induced rat OSF model, THBS1 inhibition alleviated collagen deposition and the decline in vascularity in vivo. Overall, we exploited an assembled organoid model to study OSF pathogenesis and provide a rationale for targeting THBS1.

Despite obvious tumor shrinkage, relapse after chemotherapy remains a main cause of cancer-related mortality, indicating that a subpopulation of cancer cells acquires chemoresistance and lingers after treatment. However, the mechanism involved in the emergence of chemoresistant cells remains largely unknown. Here, we demonstrate that the degradation of mitochondria via autophagy leads to a dormant state in a subpopulation of cancer cells and confers on them resistance to lethal cisplatin (DDP) exposure. The surviving DDP-resistant cells (hereafter, DRCs) have a lower metabolic rate but a stronger potential malignant potential. In the absence of DDP, these DRCs exhibit an ever-increasing self-renewal ability and heightened tumorigenicity. The combination of chloroquine and DDP exerts potent tumor-suppressive effects. In summary, our findings illuminate the mechanism between mitophagy and tumor dormancy and prove that targeting mitophagy might be a promising approach for overcoming chemoresistance in head and neck squamous cell carcinoma (HNSCC).

Nicotinamide N-methyltransferase (NNMT) has been reported to be linked to methylation reprogramming in cancer cells. However, the role of NNMT in the tumour microenvironment (TME) remains elusive. Here, we found that the expression of NNMT was elevated in the stroma of oral squamous cell carcinoma (OSCC). Using a fibroblast-attached organoids (FAOs) model, we confirmed that stromal NNMT expression contributed to the generation of assembled tumour organoids. In a tumour regeneration assay with co-implanted OSCC cells and cancer-associated fibroblasts (CAFs), the tumour-initiating activity was reduced when NNMT was silenced in CAFs. In contrast, overexpression of NNMT in paracancerous fibroblasts (PFs) accelerated tumour growth in co-inoculation experiments. Notably, fibroblast-specific NNMT can regulate type I collagen deposition in both FAOs and xenografts. Further investigations confirmed that the stromal NNMT-aggravated oncogenic activities were attenuated by treatment with inhibitors of either collagen synthesis (e.g. losartan, tranilast, and halofuginone) in fibroblasts, or the focal adhesion kinase (FAK) signal (i.e. defactinib) in cancer cells. Mechanistically, overexpression of NNMT reduced the enrichment of H3K27me3 at the promoter of the gene encoding lysyl oxidase (LOX), a key enzyme that regulates the cross-linking of collagen I. Overall, we propose that the NNMT-LOX-FAK cascade contributes to the crosstalk between cancer cells and fibroblasts during OSCC development, and that NNMT-centric extracellular matrix remodelling is a novel therapeutic target for patients with OSCC.

Nicotinamide N-methyltransferase (NNMT) has been reported to link with the methylation reprogramming in cancer cells. However, the role of NNMT in tumor microenvironment (TME) remained elusive. Here, we found that the expression of NNMT was elevated in the stroma of oral squamous cell carcinoma (OSCC). Using a fibroblast-attached organoids (FAOs) model, we found that the stromal NNMT expression contributed to the generation of assembled tumor organoids. In tumor regeneration assay with co-implanted OSCC cells and cancer-associated fibroblasts (CAFs), the tumor-initiating activity was reduced when NNMT in CAFs was silenced. On the contrary, overexpression of NNMT in paracancerous fibroblasts (PFs) accelerated the tumor growth in co-inoculation experiments. Of note, the fibroblast-specific NNMT can regulate the type I collagen deposition in both FAOs and xenograft. Further investigations confirmed that the stromal NNMT-aggravated oncogenic properties were attenuated by treatment with inhibitors targeting either the type I collagen synthesis (e.g. losartan, tranilast, halofuginone), or the focal adhesion kinase (FAK) signal (i.e. defactinib). Mechanistically, overexpression of NNMT reduced the enrichment of H3K27me3 at the promoter of gene encoding lysyl oxidase (LOX), a key enzyme that regulates cross-link formation of type I collagen. Overall, we propose that NNMT-LOX-FAK axis is essential for the intergrowth of cancer cells and fibroblasts during OSCC development, and the NNMT-centric extracellular matrix remodeling is supposed to be a novel therapeutic target for patients with OSCC.

Tumor volume increases continuously in the advanced stage, and aside from the self-renewal of tumor cells, whether the oncogenic transformation of surrounding normal cells is involved in this process is currently unclear. Here, we show that oral squamous cell carcinoma (OSCC)-derived small extracellular vesicles (sEVs) promote the proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) of normal epithelial cells but delay their apoptosis. In addition, nuclear-cytoplasmic invaginations and multiple nucleoli are observed in sEV-treated normal cells, both of which are typical characteristics of premalignant lesions of OSCC. Mechanistically, miR-let-7c in OSCC-derived sEVs is transferred to normal epithelial cells, leading to the transcriptional inhibition of p53 and inactivation of the p53/PTEN pathway. In summary, we demonstrate that OSCC-derived sEVs promote the precancerous transformation of normal epithelial cells, in which the miR-let-7c/p53/PTEN pathway plays an important role. Our findings reveal that cancer cells can corrupt normal epithelial cells through sEVs, which provides new insight into the progression of OSCC.

Background Angiogenesis is a key rate-limiting step in the process of tumour progression. Cancer-associated fibroblasts (CAFs), the most abundant component OSCC stroma, play important roles in pro-angiogenesis. Recently, the stroma “reverse Warburg effect” was proposed, and PFKFB3 has been brought to the forefront as a metabolic enzyme regulating glycometabolism. However, it remains unclear whether glycometabolism reprogramming is involved in promoting the angiogenesis of CAFs. Methods CAFs and paracancerous fibroblasts (PFs) were isolated from OSCC and adjacent tissues. We detected the pro-angiogenesis and glycometabolism phenotype of three pairs of fibroblasts. Targeted blockage of PFKFB3 or activation of PGC-1α signal was used to investigate the effect of glycolysis on regulating angiogenesis of CAFs in vitro and vivo. Results CAFs exhibited metabolic reprogramming and enhanced proangiogenic phenotype compared with PFs. Inhibition of PFKFB3-dependent glycolysis impaired proangiogenic factors (VEGF-A, PDGF-C and MMP9) expression in CAFs. Furthermore, CAFs proangiogenic phenotype was regulated by glycometabolism through the PGC-1α/PFKFB3 axis. Consistently, PGC-1α overexpression or PFKFB3 knockdown in CAFs slowed down tumour development by reducing tumour angiogenesis in the xenograft model. Conclusion CAFs of OSCC are characterised with glycometabolic reprogramming and enhanced proangiogenic phenotypes. Our findings suggest that activating PGC-1α signalling impairs proangiogenic phenotype of CAFs by blocking PFKFB3-driven glycolysis.

Autophagy is an essential catabolic process that orchestrates cellular homeostasis and plays dual roles in tumor promotion and suppression. However, the mechanism by which autophagy affects the self-renewal of cancer stem cells (CSCs) remains unclear. In this study, we investigated whether autophagy activation contributes to CSC properties of head and neck squamous cell carcinoma (HNSCC). The results showed that the autophagy level and CSC properties of HNSCC cells were elevated in response to several adverse conditions, including treatment with cisplatin, starvation, and hypoxia. Pretreatment with autophagy inhibitors, such as 3-MA and chloroquine, diminished the CSC properties acquired under adverse conditions. In addition, the isolated CSCs were endowed with stronger autophagic activity than non-CSCs, and the CSC properties were dampened when autophagy was inhibited either by 3-MA, chloroquine, or Beclin1 knockdown. Notably, the tumor-initiating activity of CSCs was decreased upon knocking down Beclin1. Further study revealed that FOXO3, a substrate for autophagy, was enriched in the nucleus of cells with lower autophagy levels. Nuclear FOXO3 directly bound to the promoter region of SOX2 and negatively regulated its transcriptional activity. Overexpression of FOXO3 decreased the expression of SOX2 and thereby impaired the CSC phenotype both in vitro and in vivo. Taken together, our findings suggest that the activation of autophagy is essential for the acquisition of CSC properties in adverse conditions and the self-renewal of CSCs. We clarify the role of autophagy in regulating the CSC phenotype and demonstrate that the noncanonical FOXO3/SOX2 axis is the intrinsic regulatory mechanism.