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: PALLD mRNA 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: PALLD mRNA 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). PALLD expression 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. PALLD mRNA 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-naïve effusions tapped at diagnosis (P = .018), although it was unrelated to other clinicopathological parameters or survival.

CONCLUSION: PALLD mRNA 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.