Prognostic value of blood-based fibrosis biomarkers in patients with metastatic colorectal cancer receiving chemotherapy and bevacizumab

Abstract

A desmoplastic colorectal cancer stroma, characterized by excess turnover of the cancer-associated fibroblast derived collagens type III and VI, can lead to reduced drug-uptake and poor treatment response. We investigated the association between biomarkers of collagen type III and VI and overall survival (OS) in patients with metastatic colorectal cancer (mCRC). Serum samples were collected from 252 patients with mCRC prior to treatment with bevacizumab and chemotherapy. Serum concentrations of biomarkers reflecting formation of collagen type III (PRO-C3) and VI (PRO-C6) and degradation of collagen type VI (C6M and C6Mα3) were determined by ELISA. The biomarkers were evaluated for associations with OS, individually, combined, and after adjusting for carcinoembryonic antigen (CEA), lactate dehydrogenase (LDH) and performance status (PS). High baseline levels (> median) of each collagen biomarker were significantly associated with shorter OS (PRO-C3: HR = 2.0, 95%CI = 1.54-2.63; PRO-C6: HR = 1.6, 95%CI = 1.24-2.11; C6M: HR = 1.4, 95%CI = 1.05-1.78; C6Mα3: HR = 1.6, 95%CI = 1.16-2.07). PRO-C3 and PRO-C6 remained significant after adjustment for CEA, LDH and PS. Weak correlations were seen between the collagen biomarkers (r = 0.03-0.59) and combining all improved prognostic capacity (HR = 3.6, 95%CI = 2.30-5.76). Collagen biomarkers were predictive of shorter OS in patients with mCRC. This supports that collagen- and CAF biology is important in CRC.

Figure 1

Schematic illustration of collagen type III and type VI with descriptions of their respective biomarker targets.

Figure 2

Serum levels of four different biomarkers reflecting (A) formation of collagen type III (PRO-C3), (B) formation of collagen type VI (PRO-C6), (C) degradation of collagen type VIα1 (C6M) and (D) degradation of collagen type VIα3 (C6Mα3) in patients with metastatic colorectal cancer with their respective reference range from healthy controls (dotted line). Black line, median. LLOD; lower limit of detection.

Figure 3

Assessment of the prognostic potential of low and high (median) (A) PRO-C3 (formation of collagen type III), (B) PRO-C6 (formation of collagen type VI), (C) C6M (degradation of collagen type VIα1) and (D) C6Mα3 (degradation of collagen type VIα3) serum levels by Kaplan Meier plots. Cox proportional-hazards regression was used to calculate the hazard ratios (HR) with 95% Cl and p-values. A p < 0.05 was considered significant.

Figure 4

Correlation between biomarker levels where compared pairwise and evaluated by the nonparametric Spearman correlation coefficient. ns, not significant. *p < 0.05. **p < 0.01. ***p < 0.001. ****p < 0.0001. A p < 0.05 was considered significant.

Figure 5

Assessment of the prognostic potential of combining the different biomarkers by Kaplan Meier plots. (A) LL; low C6M and low C6Mα3, LH or HL; low C6M and high C6Mα3 or high C6M and low C6Mα3, HH; high C6M and high C6Mα3. (B) LL; low PRO-C3 and low PRO-C6, LH or HL; low PRO-C3 and high PRO-C6 or high PRO-C3 and low PRO-C6, HH; high PRO-C6 and high PRO-C6. (C) LL; low PRO-C6 and low C6Mα3, LH or HL; low PRO-C6 and high C6Mα3 or high PRO-C6 and low C6Mα3, HH; high PRO-C6 and high C6Mα3. (D) LLLL; low PRO-3, PRO-C6, C6M and C6Mα3, L/H*; at least one low or high PRO-C3, PRO-C6, C6M or C6Mα3, HHHH; high PRO-C3, PRO-C6, C6M and C6Mα3. Univariate Cox proportional-hazards regression was used to calculate the hazard ratios (HR) with 95% Cl and p-values. A p < 0.05 was considered significant.