Atypical Mucin Expression Predicts Worse Overall Survival in Resectable Pancreatic Ductal Adenocarcinoma

Abstract

Background: Pancreatic ductal adenocarcinoma (PDAC) displays a typical mucin expression pattern which is characterized by MUC1 positive, MUC2 negative, and MUC5AC positive. More and more evidences show that mucins are involved in the development of pancreatic diseases. However, the relationship between mucin expression and prognosis of PDAC patients has been controversial in the past decades; therefore, we aim to figure out the association of mucin expression with survival in PDAC patients who underwent radical resection.

Methods: We performed immunohistochemistry (IHC) to detect the expression of MUC1, MUC2, and MUC5AC in resected PDAC specimens from Shanghai Cancer Center, Fudan University (FUSCC, n = 427) and obtained the corresponding clinical statistical data for retrospective study. Kaplan-Meier methods and Mantel-Cox tests were used to compare the survival curves, and the Cox regression model was employed for multivariate analyses to determine the independent risk factors. Survival analysis was also performed in the Queensland Centre for Medical Genomics (QCMG, n = 70) PDAC cohort to verify the conclusion.

Results: Both the FUSCC cohort and the QCMG cohort demonstrated that MUC1 absence was significantly correlated with worse overall survival (OS). The presence of MUC2 showed marginal significance in predicting shorter OS of PDAC patients, while MUC5AC had no prognostic value. In the FUSCC cohort, MUC1 absence was associated with increased proportion of stage III PDAC (p = 0.011), and MUC1 absence and MUC2 presence were associated with tumour perineural aggression (p = 0.011 and p = 0.030, respectively). Multivariable adjusted hazard ratios (HRs) for mortality of MUC1 and MUC2 were 0.492 (95% CI: 0.274-0.883, p = 0.017) and 1.596 (95% CI: 1.061-2.401, p = 0.025), respectively.

Conclusions: MUC1 absence or MUC2 presence is independently associated with poor OS among patients with resectable PDAC. MUC5AC absence tended to be associated with short-term death.

Figure 1

The expression patterns of mucins in PDAC tissues. (a) mRNA expression level of mucins in the QCMG PDAC cohort (n = 70). (b–g) Low-power-field images showing the representative positive and negative results of IHC staining mucins' expression in the FUSCC PDAC cohort. Corresponding high-power-field images were displayed in Supplementary Figure 1. (b, c) MUC1-positive expression was only considered when positive coloration located in the apical membrane of PDAC cells; (d, e) MUC2-positive expression was only considered when positive coloration was located in the cytoplasm of PDAC cells. (f, g) MUC5AC-positive expression was only considered when positive coloration was located in the cytoplasm of PDAC cells. Abbreviations: TPM: transcripts per million reads; PDAC: pancreatic ductal adenocarcinoma.

Figure 2

Survival curves of PDAC patients in relevant to mucin expression. The survival plots were plotted by Kaplan-Meier's method, and Mantel-Cox tests were used to compare the curves. (a–c) FUSCC cohort was stratified by mucins' IHC staining results. (a) MUC1-negative patients (n = 34) had worse survival compared to MUC1-positive patients (n = 392). (b) MUC2-positive patients (n = 69) tended to survive a shorter time compared to MUC2-negative patients (n = 355). (c) There was no statistical significance of overall survival between the subgroups stratified by MUC5AC expression (n = 365 and n = 47, respectively). (d) The cut-off value of 77.90 TPM stratified the QCMG cohort into the high MUC1 expression subgroup (n = 63) and the low MUC1 expression subgroup (n = 7) with a significant difference in OS. (e) The cut-off value of 0.682 TPM stratified the QCMG cohort into the high MUC2 expression subgroup (n = 47) and the low MUC2 expression subgroup (n = 23) with a marginally significant difference in OS. (f) The cut-off value of 17.83 TPM stratified the QCMG cohort into the high MUC5AC expression subgroup (n = 52) and the low MUC5AC expression subgroup (n = 18); although the survival curves had a separating tendency in the early stage, there was no statistical OS difference. Abbreviations: PDAC: pancreatic ductal adenocarcinoma.

Figure 3

Multivariate analyses of mucin expression and clinicopathological characteristics on overall survival. The univariate analysis results of the FUSCC cohort are displayed in Supplementary Table 2, and risk factors with a p value less than 0.1 in the univariate analysis were integrated to make multivariate logistic regression. The X-axis of this forest plot stands for HR, which was calculated by logistic Cox regression, enter method. The median of CA19-9 was 188.6 U/ml. Abbreviations: HR: hazard ratio; CI: confidence interval.

Figure 4

Previous studies on mucins' prognostic values in PDAC. Five investigations with reported HR values were included in this forest plot. The X-axis stands for HR. Abbreviations: HR: hazard ratio; CI: confidence interval.