Peripheral blood gene expression of B7 and CD28 family members associated with tumor progression and microscopic lymphovascular invasion in colon cancer patients

Abstract

Purpose: To associate the global gene expression of B7/CD28 family transcripts with pathologic features of colon cancer, we determined the B7/CD28 family transcripts in peripheral blood mononuclear cells (PBMCs) from normal subjects and patients with adenomatous polyps and colon cancer, and correlated the results with pathologic features of colon cancer.

Methods: PBMCs from age-matched normal subjects and patients with adenomatous polyps and colon cancer were analyzed for peripheral blood transcripts (PBTs) of B7/CD28 family using real-time PCR. Differences in expression levels of B7/CD28 PBTs across all cancer stages and between colon cancer patients with or without microscopic lymphovascular invasion (LVI) were analyzed.

Results: The results showed a significant upregulation of PBTs of co-inhibitory molecules such as B7-H3 and PD-1 and a significant PBT downregulation of co-stimulatory molecules including CD28 and ICOS in colon cancer patients. Furthermore, the increase of B7-H3 PBT was strongly associated with tumor invasion (P = 0.025) and advanced TNM stages (P = 0.019), whereas the decline of co-stimulatory ligand B7-H2 PBT was related to regional lymph node metastasis (P = 0.028) and aggressive tumor invasion (P = 0.031). In addition, the ratios of PBT expression of CD28 family to B7 family such as CTLA-4 to B7-H2 and PD-1 to B7-H2 were significantly higher in colon cancer patients with microscopic LVI than in those without LVI (P = 0.001 and P = 0.016, respectively).

Conclusions: Our results suggest that B7/CD28 family PBTs may serve as valuable markers reflecting the pathological features of colon cancer.

Fig. 1

Expression of peripheral blood transcripts of B7/CD28 family members. Total RNA was extracted from PBMCs of normal subjects and patients with adenomatous polyps or colon cancer. Quantitative real-time PCR for B7/CD28 family was performed. Gene expression levels were calculated as a relative quantification using standard curves generated by serial dilutions of human cancer cell line cDNAs containing each target gene (N normal subjects, P patients with adenomatous polyps, C patients with colon cancer)

Fig. 2

ROC curve analysis of combined PD-1 and CD28 or BTLA for differentiation of patients with TNM stage I and II colon cancer from normal subjects