Aquaporin-3 expression profile in malignant mesothelioma

Background & Objectives: Aquaporins regulate water transport in
normal and neoplastic cells. They also play a role in cell migration,
proliferation and adhesion. Preliminary data have shown AQP-1
upregulation in MM, but other aquaporin such as AQP-3 could
present disregulation and be used as potential therapeutic targets:
AQP-3 (an aquaglyceroporin expressed in the stratum corneum of
the skin) was found to be overexpressed in colorectal, cervical,
lung, oesophageal, gastric, skin and tongue (squamous) carcinomas
and in hepatocarcinomas.
Methods: Supported by preliminary biochemical results, a consecutive
series of ten MM samples was evaluated with immunohistochemistry
(Sigma Aldrich anti-AQP3 antibody) and AQP-3 expression
was compared with adjacent non-neoplastic mesothelium. We
evaluated only the positivity or negativity, regardless of the intensity
of the staining.
Results: Expression of AQP-3 was observed in 7 out of 10 cases, with a
membrane (62%) or cytoplasmic (25%) pattern of expression in up to
70% of MM cells, while expression in non-neoplastic mesothelium was
not significant. The only case of sarcomatoid malignant mesothelioma in
our series was found to be negative for AQP-3.
Conclusion: AQP-3 appears to be upregulated in 70% of our series of
MMs, with a prevalent expression on the membrane surface, where the
protein can play its natural role in water (and glycerol) exchange. The
cases where a cytoplasmatic pattern was observed, suggest us that protein
can play a pathogenetic role not only if correctly exported to the cellular
membrane, but also if accumulated in the cytoplasm.