Correlation between the expression of thrombospondin-1 and neovascularization in mucoepidermoid carcinoma:

Thrombospondin-1 induces immunogenic cell death in human mucoepidermoid carcinoma MC-3 cells via the PERK/eIF2α signaling pathway: potential implications for tumor immunotherapy

OBJECTIVE

To investigate whether Thrombospondin-1 (TSP-1) induces immunogenic cell death (ICD) in human mucoepidermoid carcinoma (MC-3) cells and explore its potential to induce calreticulin (CRT) exposure via the PERK/eIF2α signaling pathway.

METHODS

The MC-3 cell line was used as the research model. The CCK-8 assay was performed to determine the optimal seeding density, TSP-1 concentration, and treatment time. Annexin V/PI double staining combined with flow cytometry was used to assess apoptosis across different experimental groups (blank control, TSP-1, paclitaxel (PTX), TSP-1 + PTX). Cells were divided into groups: blank control, PTX, TSP-1, TSP-1 + ISRIB (ISRIB: Integrated Stress Response Inhibitor), and TSP-1 + PTX, and CRT expression was detected by flow cytometry. Immunofluorescence, Western blot, and qPCR were used to detect the expression of PERK (Protein Kinase R-like Endoplasmic Reticulum Kinase), eIF2α (eukaryotic Initiation Factor 2α), and CRT. All experiments were performed in triplicate, and data were analyzed using GraphPad Prism 8.0 software. Statistical significance was set at P < 0.05.

RESULTS

At a seeding density of 2 × 104/mL, MC-3 cells reached the growth plateau by day six. The optimal concentration and duration of TSP-1 treatment were 0.1 μmol/L and 72 h, respectively. Flow cytometry, immunofluorescence, Western blot, and qPCR results revealed that TSP-1 significantly induced CRT exposure in MC-3 cells (P < 0.05), accompanied by the upregulation of PERK and eIF2α expression (P < 0.05). Co-treatment with PTX further enhanced these effects, while the addition of ISRIB reduced the expression of PERK, eIF2α, and CRT (P < 0.05).

CONCLUSION

TSP-1 induces ICD in MC-3 cells, accompanied by CRT exposure, potentially mediated through the activation of the PERK/eIF2α signaling pathway. These findings suggest that TSP-1 may have potential as an adjunct to chemotherapy for enhancing tumor immunotherapy.

Microencapsulation of low-passage poorly-differentiated human mucoepidermoid carcinoma cells by alginate microcapsules: in vitro profiling of angiogenesis-related molecules

Background

Human mucoepidermoid carcinoma (MEC) is regarded as the most common primary salivary malignancy. High-grade MEC has a high risk of recurrence and poor prognosis. Tumor angiogenesis, induced by poorly differentiated cancer cells of high-grade MEC, contributes to tumor growth and metastasis. Therefore, elucidating molecular mechanisms underlying the pro-angiogenic ability of poorly differentiated MEC cells is critical for the understanding of high-grade MEC progression. It is well known that three-dimensional (3D) cell culture, in contrast with conventional two-dimensional (2D) culture, provides a better approach to in vitro recapitulation of in vivo characteristics of cancer cells and their surrounding microenvironment. The purpose of this study was to model a 3D environment for in vitro gene expression profiling of key molecules in poorly differentiated MEC cells for cancer neovascularization and compared them with traditional 2D cell culture.

Methods

Low-passage poorly differentiated MEC cells, derived from human patient samples of high-grade MEC, were microencapsulated in sodium alginate gel microcapsules (3D culture) and compared with cells grown in 2D culture. Cancer cell proliferation was determined by MTT assays for 1 week, and gene expression of VEGF-A, bFGF and TSP-1 was analyzed by western blotting or ELISA. The hypoxic environment in 3D versus 2D culture were assessed by western blotting or immunofluorescence for HIF1α, and the effect of hypoxia on VEGF-A gene expression in 3D cultured cancer cells was assessed by western blotting with the use of the HIF1α inhibitor, 2-methoxyestradiol (2-MeOE2).

Results

When encapsulated in alginate gel microcapsules, low-passage poorly differentiated human MEC cells grew in blocks and demonstrated stronger and relatively unlimited proliferation activities. Moreover, significant differences were found in gene expression, with 3D-grown cancer cells a significant increment of VEGF-A and bFGF and a drastic reduction of TSP-1. Consistently, 3D-grown cancer cells secreted significantly more VEGF-A than 2D culture cancer cells. Furthermore, 3D-grown cancer cells showed significantly higher expression of HIF1α, a molecular indicator of hypoxia; the increased expression of VEGF-A in 3D cultured cancer cells was shown to be dependent on the HIF1α activities.

Conclusions

The present work shows the effects of 3D culture model by alginate microencapsulation on the proangiogenic potentials of low-passage poorly differentiated human MEC cells. Cancer cells in this 3D system demonstrate significant intensification of key molecular processes for tumor angiogenesis. This is due to a better modeling of the hypoxic tumor microenvironment during 3D culture.

Derived vascular endothelial cells induced by mucoepidermoid carcinoma cells: 3-dimensional collagen matrix model

Mucoepidermoid carcinoma undergoes uniquely vigorous angiogenic and neovascularization processes, possibly due to proliferation of vascular endothelial cells (ECs) induced by mucoepidermoid carcinoma cells (MCCs) in their three-dimensional (3D) microenvironment. To date, no studies have dealt with tumor cells and vascular ECs from the same origin of mucoepidermoid carcinoma using the in vitro 3D microenvironment model. In this context, the current research aims to observe neovascularization with mucoepidermoid carcinoma microvascular ECs (MCMECs) conditioned by the microenvironment in the 3D collagen matrix model. We observed the growth of MCMECs purified by immunomagnetic beads and induced by MCCs, and characteristics of tubule-like structures (TLSs) formed by induced MCMECs or non-induced MCMECs. The assessment parameters involved the growth curve, the length, the outer and inner diameters, and the wall thickness of the TLSs, and the cell cycle. Results showed that MCCs induced formation of the TLSs in the 3D collagen matrix model. A statistically significant difference was noted regarding the count of TLSs between the control group and the induction group on the 4th day of culture (t=5.00, P=0.001). The outer and inner diameters (t(1)=5.549, P(1)=0.000; t(2)=10.663, P(2)=0.000) and lengths (t=18.035, P=0.000) of the TLSs in the induction group were statistically significant larger than those in the control group. The TLSs were formed at the earlier time in the induction group compared with the control group. It is concluded that MCCs promote growth and migration of MCMECs, and formation of the TLSs. The 3D collagen matrix model with MCMECs induced by MCCs in the current research may be a favorable choice for research on pro-angiogenic factors in progression of mucoepidermoid carcinoma.