Carbonic anhydrase XII expression is associated with histologic grade of cervical cancer and superior radiotherapy outcome

Abstract

Background: To investigate whether expression of carbonic anhydrase XII (CA12) is associated with histologic grade of the tumors and radiotherapy outcomes of the patients with invasive cervical cancer.

Methods: CA12 expression was examined by immunohistochemical stains in cervical cancer tissues from 183 radiotherapy patients. Histological grading was classified as well (WD), moderately (MD) or poorly differentiated (PD). Oligonucleotide microarray experiment was performed using seven cervical cancer samples to examine differentially expressed genes between WD and PD cervical cancers. The association between CA12 and histological grade was analyzed by chi-square test. CA12 and histological grades were analyzed individually and as combined CA12 and histologic grade categories for effects on survival outcome.

Results: Immunohistochemical expression of CA12 was highly associated with the histologic grade of cervical cancer. Lack of CA12 expression was associated with PD histology, with an odds ratio of 3.9 (P = 0.01). Microarray analysis showed a fourfold reduction in CA12 gene expression in PD tumors. CA12 expression was marginally associated with superior disease-free survival. Application of the new combined categories resulted in further discrimination of the prognosis of patients with moderate and poorly differentiated tumor grade.

Conclusions: Our study indicates that CA12 may be used as a novel prognostic marker in combination with histologic grade of the tumors.

Figure 1

Expression of CA12 in uterine cervical cancer. (A) Negative for CA12, (B) 5%, (C) 70% positive for CA12. CA12 protein was expressed at the cell membrane (Original magnification × 200).

Figure 2

Microarray analysis. (A) Microarray sample tree of 7 patients and Dendrogram. Average linkage hierarchical clustering of the seven samples using the entire 54,675 probe sets showed well differentiated (WD) and poorly differentiated (PD) tumors tended to be located more closely together in each subset. Patient 1 and 2 represent the 2 patients with WD tumor and patient 3~7 represent the 5 patients with PD tumor. CA12 gene expression was amplified and marked (thick arrow). (B) Examination of CA12 mRNA quantity by real-time PCR. The quantity of CA12 gene was expressed as a ratio of mean quantity of CA12 to β-actin.

Figure 3

Survival Distributions(DFS, LRFS)by CA12 expression. Disease-free survival (DFS) (A) and Local recurrence-free survival (B) by CA12 expression. p-values are for log rank test.

Figure 4

Survival Distributions(DFS,LRFS) by histologic grades. Disease-free survival (DFS) (A) and Local recurrence-free survival (B) by histologic grades. p-values are for log rank test.

Figure 5

Survival Distributions(DFS,LRFS) by new combined categories. Disease-free survival (DFS) (A) and Local recurrence-free survival (B) by new combined categories. p-values are for log rank test.