ASB6 Promotes the Stemness Properties and Sustains Metastatic Potential of Oral Squamous Cell Carcinoma Cells by Attenuating ER Stress

Abstract

Up-regulation of ASB6 has been previously associated with late-stage and poor prognosis of oral squamous cell carcinoma (OSCC) patients. To explore the cellular and molecular basis of how ASB6 enhances the malignancy of OSCC, we employed the clonogenicity and migration assays, murine pulmonary metastasis model, Western blot, and immunofluorescence microscopy to characterize the phenotypes of OSCC cells with lentiviral-based stable overexpression or knockdown of ASB6. We found that ASB6 overexpression increases, whereas ASB6 knockdown decreases, the potential of tumor-sphere formation, colony formation, and expression of Oct-4 and Nanog. While knockdown of ASB6 decreases cell migration in vitro and lung metastasis in mice, the migratory potential was however not promoted by ASB6 overexpression. ASB6 knockdown down-regulates the level of vimentin, and the loss of filopodia formation became more prominent following CRISPR/Cas9-directed knockout of ASB6. Moreover, ASB6 was up-regulated when cells were grown in selective condition featured with a collateral effect of enhancing intracellular stress, and the level of endoplasmic reticulum (ER) stress was further increased by knockdown of ASB6. Thus, ASB6 may attenuate ER stress that would otherwise accumulate and subsequently impede the potential of cells to acquire or sustain the stemness properties and metastatic capacity, thereby enhancing the malignancy of OSCC by increasing the population of cancer stem or stem-like cells.

Evaluation of potential anti-metastatic and antioxidative abilities of natural peptides derived from Tecoma stans (L.) Juss. ex Kunth in A549 cells

“…The up-regulation of ASB6 is associated with the elevation of intracellular ROS in oral cancer cells ( Hung et al, 2009 ). A recent study also showed that overexpression of ASB6 can decrease intracellular ROS and endoplasmic reticulum stress in the deprived media-induced stress of oral cancer cells ( Hung et al, 2019 ). Therefore, the reduction of intracellular ROS in the LPS-stimulated cells ( Fig.…”

CUL5–ASB6 Complex Promotes p62/SQSTM1 Ubiquitination and Degradation to Regulate Cell Proliferation and Autophagy

“…Later, ASB6 was found upregulated in oral squamous cell carcinoma, which is a possible consequence of exposure to Areca nut extracts and is co-related with poor survival ( Hung et al, 2009 ). Another recent following study from the same group suggested that accumulation of ASB6 may impede ER stress and cause gain of stemness and metastasis feature of oral squamous cell carcinoma, although the underlying molecular mechanism remains elusive ( Hung et al, 2019 ). Therefore, the detailed molecular function of ASB6, especially in pathological conditions, is largely unknown.…”

Role of the Inflammatory Response of RAW 264.7 Cells in the Metastasis of Novel Cancer Stem-Like Cells

“…During monocyte differentiation by macrophage colony stimulating factor (M-CSF), the ER undergoes structural as well as functional reorganization to perform the new cell functions, leading to ER stress and upregulated UPR [31] The UPR is a pro-survival mechanism that is activated and regulates cells by maintaining protein homeostasis via accumulation of unfolded, misfolded, and immature proteins in the ER; however, the UPR can also trigger cell death under unresolved levels of improper protein accumulation [32,33]. Moreover, aberrant activation of endoplasmic reticulum stress (ER stress) has been considered to have a major role in the regulation of tumor growth, invasion, metastasis, and its microenvironment, as well as in response to chemotherapy, targeted therapies, and immunotherapy [34,35]. The alleviation of ER stress prevents the otherwise increasing potential of cells to acquire or sustain stem-cell properties and metastatic capacity, thereby enhancing the malignancy of oral squamous cell carcinoma cells by increasing the population of cancer stem or stem-like cells [36].…”