Expression of palladin is associated with disease progression in metastatic high-grade serous carcinoma.

Objective To analyse the expression and clinical role of the actin-associated molecule palladin in serous effusions. Methods PALLDmRNA expression was analysed by quantitative reverse transcription polymerase chain reaction in 83 high-grade serous carcinoma (HGSC) effusions. Fifteen malignant mesothelioma (MM) effusions and 18 surgical HGSC specimens from the ovary were studied for comparative purposes. Palladin protein expression by immunohistochemistry was analysed in another series consisting of 261 HGSC effusions. Results PALLDmRNA was significantly overexpressed in HGSC compared to MM effusions (P < .001). Palladin expression by immunohistochemistry was found in HGSC cells in 106/261 (41%) effusions, most commonly focally (<5% of cells).PALLDexpression was additionally higher in ovarian HGSC specimens compared to HGSC effusions (P < .001). However, immunohistochemistry showed only stromal expression of this protein in surgical specimens.PALLDmRNA expression in HGSC effusions was unrelated to clinicopathological parameters, chemotherapy response or survival. Palladin protein expression was higher in post-chemotherapy, mainly disease recurrence, specimens compared to chemo-naive effusions tapped at diagnosis (P = .018), although it was unrelated to other clinicopathological parameters or survival. Conclusion PALLDmRNA is overexpressed in HGSC compared to MM effusions, and its protein product is overexpressed in post-chemotherapy compared to pre-chemotherapy HGSC effusions, suggesting upregulation along tumour progression. The presence of this molecule in HGSC effusions, at the mRNA or the protein level, is unrelated to disease outcome.