Expression of the RNase III enzyme DROSHA is reduced during progression of human cutaneous melanoma

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Aberrant microRNA (miRNA) biogenesis factor expression is linked to various cancers.
• Previous research indicated reduced DICER1 expression in metastatic melanoma.
• The expression patterns of other miRNA biogenesis factors, like DROSHA, in melanoma remain largely uncharacterized.

Purpose of the Study:

• To investigate the expression pattern of DROSHA in a large cohort of melanocytic lesions.
• To correlate DROSHA expression with melanoma progression and clinical parameters.
• To examine the relationship between DROSHA and DICER1 expression and patient outcomes.

Main Methods:

• Tissue microarray and immunohistochemistry were employed on 409 melanocytic lesions.
• Two distinct antibodies targeting different regions of DROSHA were used for validation.
• Statistical analyses were performed to assess correlations between DROSHA expression and clinicopathological features.

Main Results:

• Nuclear DROSHA expression was significantly reduced in early melanoma stages, inversely correlated with tumor thickness, AJCC stage, and ulceration.
• Reduced nuclear DROSHA was accompanied by increased cytoplasmic expression during melanoma progression.
• Concomitant loss of DROSHA and DICER1 expression was associated with a worse prognosis in melanoma patients.

Conclusions:

• The study demonstrates reduced nuclear DROSHA expression in melanoma, indicating a perturbed miRNA biogenesis pathway.
• Aberrant subcellular localization of DROSHA suggests deregulation of its nuclear import mechanisms.
• Combined loss of DROSHA and DICER1 highlights their critical roles in melanoma progression and patient outcomes.