Biphasic Expression of Atypical Chemokine Receptor (ACKR) 2 and ACKR4 in Colorectal Neoplasms in Association with Histopathological Findings

Abstract

Facilitating resolution of inflammation using atypical chemokine receptors (ACKR) as an anticancer strategy is considered but requires a deeper understanding of receptor role in carcinogenesis. We aimed at transcriptional analysis (RTqPCR) of ACKR2 and ACKR4 expression in colorectal adenoma-adenocarcinoma sequence in paired normal-neoplastic tissues from 96 polyps and 51 cancers. On average, ACKR2 was downregulated in neoplastic as compared to non-affected tissue in polyp (by 2.7-fold) and cancer (by 3.1-fold) patients. The maximal downregulation (by 8.2-fold) was observed in adenomas with the highest potential for malignancy and was gradually lessening through cancer stages I-IV, owing to increased receptor expression in tumors. On average, ACKR4 was significantly downregulated solely in adenocarcinomas (by 1.5-fold), less so in patients with lymph node metastasis, owing to a gradual decrease in ACKR4 expression among N0-N1-N2 cancers in non-affected tissue without changes in tumors. In adenomas, ACKR4 downregulation in neoplastic tissue increased with increasing potential for malignancy and contribution of villous growth pattern. ACKR4 expression increased in non-affected tissue with a concomitant decrease in pathological mucosa. In conclusion, the changes in ACKRs expression occur already in precancerous colorectal lesions, culminating in the adenomas with the highest potential for malignancy. Therefore, chemoprevention by manipulating ACKRs' expression is worth exploration.

Keywords: CC chemokines; chemoprevention; colorectal adenomas; colorectal cancer; decoy receptors; resolution of inflammation.

Figure 1

Expression of atypical chemokine receptors (ACKR) in colorectal polyps: (a) ACKR2; (b) ACKR4. Data presented as dot-plots and mean (95% confidence interval) and analyzed using t-test for paired samples. NRQ, normalized relative quantity.

Figure 2

Impact of adenoma histological type on ACKR4 expression: (a) normal–to-polyp expression ratio (N/P); (b) in normal tissue; (c) in adenomas. Data presented as dot-plots with medians with 95% confidence interval (figures below the dot-plots and red triangles with whiskers) and analyzed using a Kruskal–Wallis H test with a Conover post hoc test. Groups differing significantly in a post hoc analysis are indicated by the same type of symbol: *, #, or ^. T, tubular adenomas; T-V, tubulovillous adenomas; V, villous adenomas; NRQ, normalized relative quantity.

Figure 3

Pairwise analysis of ACKR4 expression in patients stratified by adenoma histological type: (a) tubular adenomas; (b) tubulovillous adenomas; (c) villous adenomas. Data presented as dot-plots and mean (95% confidence interval) and analyzed using t-test for paired samples. NRQ, normalized relative quantity.

Figure 4

Impact of polyp cumulated risk for malignancy on expression ratio (normal-to-polyp) (N/P) of: (a) ACKR2; (b) ACKR4. Data presented as means with 95% confidence interval (figures below the dot-plots and red triangles with whiskers) and analyzed using one-way analysis of variance with Students–Newman–Keuls post hoc test. Groups differing significantly in a post hoc analysis are indicated by the same type of symbol: *, #, or ^.

Figure 5

Expression of atypical chemokine receptors (ACKR) in colorectal adenocarcinomas: (a) ACKR2; (b) ACKR4. Data presented as dot-plots and mean (95% confidence interval) and analyzed using t-test for paired samples. NRQ, normalized relative quantity.

Figure 6

Association between ACKR2 expression and depth of tumor invasion. Data presented as Spearman correlation coefficient rho (ρ) represented graphically as a red trend line. N/T, expression ratio normal-to-tumor.

Figure 7

Impact of lymph node involvement on ACKR4 expression: (a) normal–to-tumor expression ratio (N/T); (b) in macroscopically normal tissue; (c) in tumors. Data presented as dot-plots with means with 95% confidence interval (figures below the dot-plots and red triangles with whiskers) and analyzed using t-test for independent samples. NRQ, normalized relative quantity.

Figure 8

Correlation between cancer N stage and ACKR4 expression: (a) as a normal–to-tumor expression ratio (N/T); (b) in macroscopically normal tissue; (c) in tumors. Data presented as Spearman correlation coefficient rho (ρ) represented graphically as a red trend line. NRQ, normalized relative quantity.

Figure 9

Impact of polyp risk for malignancy and cancer malignant potential on (a) ACKR2 expression ratio (normal-to-pathological) (N/P); (b) ACKR2 expression in normal mucosa; (c) ACKR2 expression in pathological tissue (adenoma or adenocarcinoma). Data presented as means with 95% confidence interval (red triangles with whiskers). The relationship was analyzed using Spearman rank correlation and expressed as correlation coefficient ρ. NRQ, normalized relative quantity.

Figure 10

Impact of polyp risk for malignancy and cancer malignant potential on (a) ACKR4 expression ratio (normal-to-pathological) (N/P); (b) ACKR4 expression in normal mucosa; (c) ACKR4 expression in pathological tissue (adenoma or adenocarcinoma). Data presented as means with 95% confidence interval (red triangles with whiskers). The relationship was analyzed using Spearman rank correlation and expressed as correlation coefficient ρ. NRQ, normalized relative quantity.