Melanoma secretion of transforming growth factor-β2 leads to loss of epidermal AMBRA1 threatening epidermal integrity and facilitating tumour ulceration

BACKGROUND

For patients with early American Joint Committee on Cancer (AJCC)-stage melanoma the combined loss of the autophagy regulatory protein AMBRA1 and the terminal differentiation marker loricrin in the peritumoral epidermis is associated with a significantly increased risk of metastasis.

OBJECTIVES

The aim of the present study was to evaluate the potential contribution of melanoma paracrine transforming growth factor (TGF)-β signalling to the loss of AMBRA1 in the epidermis overlying the primary tumour and disruption of epidermal integrity.

METHODS

Immunohistochemistry was used to analyse AMBRA1 and TGF-β2 in a cohort of 109 AJCC all-stage melanomas, and TGF-β2 and claudin-1 in a cohort of 30 or 42 AJCC stage I melanomas, respectively, with known AMBRA1 and loricrin (AMLo) expression. Evidence of pre-ulceration was analysed in a cohort of 42 melanomas, with TGF-β2 signalling evaluated in primary keratinocytes.

RESULTS

Increased tumoral TGF-β2 was significantly associated with loss of peritumoral AMBRA1 (P < 0·05), ulceration (P < 0·001), AMLo high-risk status (P < 0·05) and metastasis (P < 0·01). TGF-β2 treatment of keratinocytes resulted in downregulation of AMBRA1, loricrin and claudin-1, while knockdown of AMBRA1 was associated with decreased expression of claudin-1 and increased proliferation of keratinocytes (P < 0·05). Importantly, we show loss of AMBRA1 in the peritumoral epidermis was associated with decreased claudin-1 expression (P < 0·05), parakeratosis (P < 0·01) and cleft formation in the dermoepidermal junction (P < 0·05).

CONCLUSIONS

Collectively, these data suggest a paracrine mechanism whereby TGF-β2 causes loss of AMBRA1 overlying high-risk AJCC early-stage melanomas and reduced epidermal integrity, thereby facilitating erosion of the epidermis and tumour ulceration.

Reduction in skin cancer diagnoses in the UK during the COVID-19 pandemic

The UK healthcare system, including skin cancer departments, has been profoundly affected by the COVID‐19 pandemic. Despite service capacity and a worldwide increase in incidence, anecdotal reports suggest a decline in skin cancer diagnoses following COVID‐19. To determine if there has been a decrease in skin cancer diagnosis in the UK in the COVID‐19 era, we analysed data from the Northern Cancer Network from 23 March 2020 to 23 June 2020 and compared it with the same period in 2019 (pre‐COVID). In the COVID period, there was a decrease of 68.61% in skin cancer diagnoses, from 3619 to 1136 (P < 0.01). Surprisingly, skin cancer waiting times were also reduced in the COVID period compared to the pre‐COVID period (median of 8 and 12 days, respectively; P < 0.001). Collectively, these data highlight a statistically significant reduction in both skin cancer diagnoses and waiting times during the COVID period.

The Kupffer cell in experimental extrahepatic cholestasis in the rat--a light microscopy, immunohistochemical and electron microscopy study

Kupffer cell phagocytic function is reduced in the presence of obstructive jaundice. To investigate possible mechanisms we report a study of the rat liver in extrahepatic cholestasis, using light microscopy, immunohistochemistry and electron microscopy, Immunohistochemistry was performed with monoclonal antibodies specific for rat Kupffer cells ED 1, ED 2 and ED 3 and monoclonal antibodies directed against class II antigens of the rat major histocompatibility complex Ox 3 and Ox 6. Extrahepatic cholestasis was produced by bile duct ligation. In bile duct ligated animals light microscopy showed proliferation of bile ductules and an increase in sinusoidal cells. Immunohistochemistry with ED 1, ED 2 and ED 3 demonstrated a marked increase in the number of positive cells, but few of these cells were positive with Ox 3 and Ox 6, whereas the proliferating bile ductules were strongly positive. Electron microscopy revealed two homogeneous granular substances within the sinusoidal lumen and loss of the space of Disse. Despite a reduction in Kupffer cell phagocytic function in obstructive jaundice there is an increase in Kupffer cells, but these cells appear to be in an inactivated state as few express class II antigens on their surface. Furthermore the granular substance within the space of Disse may interfere with function.