Upregulation of COL6A1 is predictive of poor prognosis in clear cell renal cell carcinoma patients

Abstract

Background: The extracellular matrix (ECM) is reported to play an important role in tumorigenesis and progression. Collagen VI is an important ECM protein. In this study, we investigated the potential role of the COL6A1 gene, which encodes the α1 polypeptide of collagen VI, in the biological functions involved in the progression and outcome of clear cell renal cell carcinoma (ccRCC).

Materials and methods: A total of 288 ccRCC patients who underwent radical nephrectomy (RN) or nephron sparing nephrectomy (NSS) at Fudan University Shanghai Cancer Center (FUSCC) were enrolled. Total RNA was extracted from frozen samples obtained from the tissue bank of FUSCC and expression of COL6A1 was determined by qRT-PCR. The clinical relationship between COL6A1 expression and ccRCC prognosis was analyzed. These data were then validated in the Cancer Genome Atlas (TCGA) cohort. We also investigated the effect of COL6A1 overexpression in a xenografted tumor model in nude mice in vivo.

Results: In multivariate analysis of TCGA cohorts, COL6A1 high expression was predictive of poor prognosis in ccRCC patients' overall survival (OS) (HR: 2.588 95%CI 1.616-4.146) and disease free survival(DFS) (HR: 3.106 95%CI 1.534-6.288). In FUSCC cohorts, after adjusted for relevant factors, the COL6A1 expression indicates poor prognosis in ccRCC patients's OS (HR 2.211; 95% CI, 1.360-8.060) and DFS (HR 3.052; 95%CI, 1.500-6.210). COL6A1 overexpression promoted tumor growth in xenografted nude mice.

Conclusion: Increased COL6A1 expression correlates with poor prognosis in ccRCC patients. Moreover, COL6A1 stimulates tumor growth in vivo.

Keywords: COL6A1; clear cell renal cell carcinoma; prognosis; tumorigenesis.

Figure 1. Kaplan–Meier plots of survival are shown according to COL6A1 expression

A. Kaplan-Meier estimates of disease-free survival (DFS) in the Cancer Genome Atlas (TCGA) cohort. The median survival time of high and low expressers was 79.1 versus 95.3 months. B. Kaplan–Meier plots of overall survival (OS) in TCGA cohort. The median survival time of high and low expressers was 85.7 versus 108.6 months. C, D. Kaplan–Meier estimates of DFS and OS in FUSCC cohort. The median survival time of high and low expressers was 69.7 versus 75.6 months for DFS and 71.4 versus 78.1 for OS.

Figure 2. Kaplan–Meier plot of progression free survival (PFS) is shown according to COL6A1 expression

A total of 41 patients received sunitinib treatment. The median survival time of high and low expressers was 5.8 versus 21.67 months.

Figure 3. COL6A1 IHC score was correlated with mRNA level

A. The two photographs (400X) showed negative (a) and positive (b) staining of COL6A1 in ccRCC. B. The comparison of relative COL6A1 mRNA level (normalized to β-actin) between low and high IHC score groups. Relative COL6A1 mRNA level in high IHC score group were significant higher than low IHC score group.

Figure 4. COL6A1 promotes 7860 tumor growth in nude mice

A. 7860 cells were stably infected with the oe-COL6A1 and oe-Mock control particles. COL6A1 expression was determined by qRT-PCR and normalized to β-actin expression. B. COL6A1 promoted tumor growth in nude mice. Tumor volume was measured with Vernier calipers every 3 days and compared. C, D. The mice were humanely sacrificed on Day 56, and the tumors were weighed and photographed (P = 0.062). Data represent the mean ± standard deviation (SD).