Wnt5a in breast cancer: An independent factor for decreased invasiveness and cancer-related death

Introduction: Wnt5a signals noncanonically through frizzled receptors and do not liberate beta-catenin. It has been reported both as a putative oncogene or tumor suppressor in different tumors and its role is also not clear in breast cancer. Therefore, we aimed to evaluate the expression of Wnt5a and other selected proteins in breast cancer, normal tissues and precursor lesions and the role in breast cancer progression.

Materials and Methods: Archival formalin-fixed paraffinembedded 173 invasive breast cancer samples classified into WHO histotypes [invasive ductal (97), lobular (53) and other (22)] and luminal, triple negative and Her2 immunohistochemical subtypes [based on expression of hormone receptors and Her2] were immunohistochemically stained with Wnt5a (Abcam, rabbit polyclonal), beta-catenin (Santa Cruz, mouse monoclonal, clone sc-7963), E-cadherin (Dako, mouse monoclonal, clone IR059) antibodies. Staining was evaluated using a histoscore (percentage positivity of area of interest stained multiplied by staining intensity). The data were statistically processed using non-parametric Mann-Whitney U test, Spearman correlation coefficient, Pearson Chi-Square, as well as ordinal and logistic regression analyses.

Results: Expression of Wnt5a protein was lost in 51.5 % of breast cancer samples. Its expression was higher in normal tissues (p=0.042), and precursor lesions (p=0.001) in comparison to breast cancer group. Wnt5a was significantly higher in ILC, than in IDC (p<0.001). Wnt5a was also higher in ILC patients with membrane-associated beta-catenin in comparison to negative ones (p=0.029), and in E-cadherin-positive ILC patients in comparison to E-cadherin-negative group (p=0.048). Luminal subtype showed higher expression of Wnt5a in comparison to Her2 and triple negative groups (both p<0.001) while its expression was equivalent in Her2 and triple negative groups. Wnt5a positively correlated with estrogen and progesterone receptors in moderate and high grade (G2 and G3) patients (ER r=0.472 and r=0.452, respectively, both p<0.01; PR r=0.445 and r=0.498, respectively p<0.01) and in patients with negative lymph node status (ER r=0.507 and PR r=0.474; both p<0.001). Weak negative association was observed in relation to stage of the disease in non-relapsing (r=-0.251, p=0.029) and lymph node negative (r=-0.237, p=0.047) patients. In this sense, Wnt5a expression was higher in patients who did not relapse in comparison to patients with progression to distant organs (p=0.026). Ordinal regression analysis revealed that odds of being patients in lower grade is 17.2 % when Wnt5a expression increases in each 10 score [95% CI 4.7% - 29.6% (p=0.007; OR=0.983)]. Likewise, increase in Wnt5a expression by each 10 score decreased odds of cancer-related death by 22% [95% CI 8% - 36% ( p=0.003 OR=0.978)].

Conclusions: Our results indicate that Wnt5a is an independent factor determining decreased invasiveness and cancer-related death in breast cancer patients. This is in concordance with other studies reporting Wnt5a as a tumor suppressor in breast cancer, however, further functional experiments should better clarify its role, in particular in the complex tumor microenvironment.

Acknowledgements: Supported by grants EU infrastructure support CZ.1.05/2.1.00/01.0030 and LF_2012_019.