To Örebro University

Introduction: Autophagy and mitophagy are key homeostatic machineries linked to cancer development and drug resistance.

Aim(s): To assess the levels of autophagy and mitophagy in well differentiated pancreatic neuroendocrine neoplasms (PanNENs) and correlate them with clinico-pathological parameters. 

Materials and methods: Fluorescent immunostaining for the autophagy markers LC3 Βand p62/or LAMP1 was performed on 22 PanNENs and 11 controls of normal pancreatic tissues and validated through Western blotting. Autophagy quantitative scoring was generated for LC3B-positive puncta and analyzed in relation to clinico-pathological parameters. TOMM20/LC3B qualitative assessment of mitophagy levels was undertaken by fluorescent immunostaining. The presence of autophagy/mitophagy was validated by transmission electron microscopy.

Results: Autophagy levels (LC3B-positive puncta/cell) were discriminative for normal vs. NEN pancreatic tissue (p=0.007). A significant association was observed between autophagy levels and tumour grade (Ki67<3% vs. Ki67≥3%; p=0.021), but not functionality (p=0.266) size (cut-off of 20mm; p=0.808), local invasion (p=0.481), lymph node- (p=0.849) and distant metastases (p=0.699). Qualitative assessment of TOMM20/LC3B demonstrated strong mitophagy levels in PanNENs by fluorescent immunostaining as compared to normal tissue. Transmission electron microscopy revealed enhanced autophagy and mitophagy in PanNEN tissue. Response to molecular targeted therapies in metastatic cases (n=4) did not reveal any patterns of association to autophagy levels.

Conclusion: Increased autophagy levels are present in primary tumours of patients with PanNENs and are partially attributed to upregulated mitophagy. Grade was the only clinico-pathological parameter associated with autophagy scores.