Expression of PTGS2 along with genes regulating VEGF signalling pathway and association with high-risk factors in locally advanced oral squamous cell carcinoma

Abstract

Background: PTGS2 encodes cyclooxygenase-2 (COX-2), which catalyses the committed step in prostaglandin synthesis. Various in vivo and in vitro data suggest that COX-2 mediates the VEGF signalling pathway. In silico analysis performed in TCGA, PanCancer Atlas for head and neck cancers, demonstrated significant expression and co-expression of PTGS2 and genes that regulate VEGF signalling. This study was designed to elucidate the expression pattern of PTGS2 and genes regulating VEGF signalling in patients with locally advanced oral squamous cell carcinoma (OSCC).

Methodology: Tumour and normal tissue samples were collected from patients with locally advanced OSCC. RNA was isolated from tissue samples, followed by cDNA synthesis. The cDNA was used for gene expression analysis (RT-PCR) using target-specific primers. The results obtained were compared with the in silico gene expression of the target genes in the TCGA datasets. Co-expression analysis was performed to establish an association between PTGS2 and VEGF signalling genes.

Results: Tumour and normal tissue samples were collected from 24 OSCC patients. Significant upregulation of PTGS2 expression was observed. Furthermore, VEGFA, KDR, CXCR1 and CXCR2 were significantly upregulated in tumour samples compared with paired normal samples, except for VEGFB, whose expression was not statistically significant. A similar expression pattern was observed in silico, except for CXCR2 which was highly expressed in the normal samples. Co-expression analysis showed a significant positive correlation between PTGS2 and VEGF signalling genes, except for VEGFB which showed a negative correlation.

Conclusion: PTGS2 and VEGF signalling genes are upregulated in OSCC, which has a profound impact on clinical outcomes.

Keywords: PTGS2; VEGF; Oral cancer; angiogenesis; gene expression; metastasis.

FIGURE 1

(A) The differential gene expression analysis of I. PTGS2, II. VEGFA, III. VEGFB, IV. KDR, V. CXCR1 and VI. CXCR2 genes in OSCC tumour samples as compared to normal. (*p < 0.05 and ^ns p >0.05) (n = 24). (B) The differential gene expression analysis of PTGS2, VEGFA, VEGFB, KDR, CXCR1 and CXCR2 genes in OSCC tumour samples (n = 24) based on gender stratification, that is, male (n = 16) and female (n = 8), where ***p = 0.001 and **p = 0.01.

FIGURE 2

(A) The gene expression analysis of PTGS2, VEGFA, VEGFB, KDR, CXCR1 and CXCR2 genes in OSCC tumour samples (n = 24) based on smokeless tobacco consumption status, that is, tobacco consumers (n = 16) and non‐consumers (n = 8), where ***p = 0.001, **p = 0.01 and *p < 0.05. (B) The gene expression analysis of PTGS2, VEGFA, VEGFB, KDR, CXCR1 and CXCR2 genes in OSCC tumour samples (n = 24) based on recurrence status, that is, recurrence positive (n = 6) and recurrence negative (n = 18), where ***p = 0.001, **p = 0.01 and *p < 0.05.

FIGURE 3

(A) The gene expression analysis of PTGS2, VEGFA, VEGFB, KDR, CXCR1 and CXCR2 genes in OSCC tumour samples (n = 24) based on cancer stage (AJCC), that is, stage 3 (n = 7) and stage 4 (n = 17), where ***p = 0.001. (B) The gene expression analysis of PTGS2, VEGFA, VEGFB, KDR, CXCR1 and CXCR2 genes in OSCC tumour samples (n = 24) based on cancer grade (AJCC), that is, grade 1 (n = 12) and grade 2 (n = 12), where ***p = 0.001, **p = 0.01 and *p < 0.05.

FIGURE 4

(A) The gene expression analysis of PTGS2, VEGFA, VEGFB, KDR, CXCR1 and CXCR2 genes in OSCC tumour samples (n = 24) based on nodal metastasis status, that is, pN0 (n = 7), pN1 (n = 6), pN2 (n = 6) and pN3 (n = 5), where ***p = 0.001, **p = 0.01 and *p < 0.05. (B) The gene expression analysis of PTGS2, VEGFA, VEGFB, KDR, CXCR1 and CXCR2 genes in OSCC tumour samples (n = 24) based on extranodal extension (ENE) status, that is, ENE‐positive (n = 6) and ENE negative (n = 18), where ***p = 0.001, **p = 0.01 and *p < 0.05.

FIGURE 5

The gene expression analysis of genes, that is, I. PTGS2, II. VEGFB, III. VEGFA, IV. KDR, V. CXCR1 and VI. CXCR2 in head and neck squamous cell carcinoma based on patient gender as compared to normal samples using the UALCAN web server (***p = 0.001).

FIGURE 6

(A) The gene expression analysis of genes, that is, I. PTGS2, II. VEGFB, III. VEGFA, IV. KDR, V. CXCR1 and VI. CXCR2 in head and neck squamous cell carcinoma based on individual cancer stage using the UALCAN web server (***p = 0.001). (B) The gene expression analysis of genes, that is, I. PTGS2, II. VEGFB, III. VEGFA, IV. KDR, V. CXCR1 and VI. CXCR2 in head and neck squamous cell carcinoma is based on nodal metastasis status using the UALCAN web server (***p = 0.001).

FIGURE 7

Co‐expression analysis in OSCC samples (n = 24) between I. KDR versus PTGS2, II. VEGFA versus PTGS2, III. VEGFB versus PTGS2, IV. CXCR1 versus PTGS2 and V. CXCR2 versus PTGS2 (R = Pearson correlation coefficient).