FP07 Impaired autophagy signalling in cutaneous squamous cell carcinoma: a novel therapeutic target
Abigail Fitzsimons, Ankit Patel, Jun Wang, Tania Maffucci, Catherine Harwood, Daniele BergamaschiAbstract
Introduction and aims
Cutaneous squamous cell carcinoma (cSCC) is the second most common form of keratinocyte cancer and the majority arise in premalignant lesions known as actinic keratoses (AKs). While most cSCC are cured by surgery, a small proportion are high-risk and may progress to locoregional metastatic disease. Investigating alterations in cellular signalling processes may reveal what drives cSCC development, progression and poor outcomes. Autophagy is a key process in which cellular waste is sequestered into autophagosomes and degraded before causing harm to the cell. A high mutational frequency of autophagy-related genes in cSCC and AK has been found in RNA sequencing databases. We hypothesize that deregulation of autophagy contributes to driving the progression of cSCC and targeting this pathway could provide novel preventive and therapeutic approaches.
Methods
Integrity of autophagic flux was investigated in a panel of 10 AK/cSCC cell lines via Western blot assay. Autophagic impairment was further investigated in AK and cSCC tissue using the Cell DIVE multiplex immunofluorescence platform, where accumulation of key autophagic proteins (LC3 and autophagy cargo receptors) indicates failed autophagic clearance.
Results
Impaired autophagic flux was observed in premalignant cSCC cell lines, while metastatic cells exhibit intact flux. In AK lesions autophagy marker accumulation was more pronounced in regions of severe dysplasia. Although tumour masses showed overall increased autophagy marker accumulation compared with perilesional epidermis and dermis, expression remained highly heterogeneous across different tumour samples. Based on the observed patterns, tumours were either autophagy-deficient or autophagy-intact. Autophagy-intact tumours were well differentiated, highly keratinized and low stage, whereas autophagy-deficient tumours were generally poorly differentiated and advanced stage.
Conclusions
Autophagy impairment may contribute to formation of premalignant AK lesions from normal epidermis. In contrast, cSCC tumours were either autophagy-deficient or intact, which may correlate with locoregional metastatic risk. Future work will elucidate how these distinct autophagy states influence tumour progression.