Reduced SMAD2/3 activation independently predicts increased depth of human cutaneous squamous cell carcinoma

Abstract

The incidence of cutaneous squamous cell carcinoma (cSCC) is rising. Whilst the majority are cured surgically, aggressive metastatic cSCC carry a poor prognosis. Inactivating mutations in transforming growth factor beta (TGF-β) receptors have been identified amongst genetic drivers of sporadic tumours and murine models of cSCC, suggesting a tumour suppressor function for TGF-β in normal skin. However, paradoxically, TGF-β acts as a tumour promoter in some murine model systems. Few studies have analysed the role of TGF-β/activin signalling in human normal skin, hyper-proliferative skin disorders and cSCC. Antibodies recognising phospho-SMAD proteins which are activated during canonical TGF-β/activin signalling were validated for use in immunohistochemistry. A tissue microarray comprising FFPE lesional and perilesional tissue from human primary invasive cSCC (n=238), cSCC in-situ (n=2) and keratocanthoma (n=9) were analysed in comparison with tissues from normal human scalp (n=10). Phosphorylated SMAD2 and SMAD3 were detected in normal interfollicular epidermal keratinocytes and were also highly localised to inner root sheath, matrix cells and Keratin 15 positive cells. Lesional cSCC tissue had significantly reduced activated SMAD2/3 compared to perilesional tissue, consistent with a tumour suppressor role for SMAD2/3 activators in cSCC. Increased cSCC tumour thickness inversely correlated with the presence of phospho-SMADs in tumour tissue suggesting that a reduction in canonical TGF-β/activin signalling may be associated with disease progression.

A Unique Panel of Patient-Derived Cutaneous Squamous Cell Carcinoma Cell Lines Provides a Preclinical Pathway for Therapeutic Testing

“…Sensitivity to MEK inhibition was seen across all lines at high concentration, low concentration-response between lines was heterogenous. MEK inhibition may be a basis for molecularly targeted cSCC chemoprevention and therapy.[67]SCCIC18Activated SMAD2/3 was significantly reduced in perilesional cSCC and, to a greater extent, lesional cSCC tissue. Increased tumour thickness inversely correlates with phospho-SMAD presence.…”

Heterogeneous addiction to transforming growth factor‐beta signalling in recessive dystrophic epidermolysis bullosa‐associated cutaneous squamous cell carcinoma*

“…We recently reported that TGF‐β canonical signalling as measured by PO 4 ‐SMAD3 expression was primarily localized to the hair follicle stem cells in normal skin, is active in perilesional and cSCC tissue, and decreased with markers of disease progression 17–19 . We employed the same method using tissue sections from six patients with RDEB cSCC, and detected nuclear localization of PO 4 ‐SMAD3 in all RDEB cSCC samples (representative samples shown in Figure 1a).…”

“…Using our published immunohistochemistry protocol 19 for detecting PO 4 ‐SMAD3 (ab52903; Abcam), 4‐μm‐thick cryosections or formalin‐fixed paraffin‐embedded tissue sections were stained and imaged as previously described.…”

“…17 Mutational alteration in TGF-b signalling, 18 and reduction in canonical signalling activity correlates with markers of disease progression. [17][18][19] In contrast, mutations in TGFBR1 or TGFBR2 have not been found in RDEB cSCC, 20 indicative of potential tumour-promoting canonical TGF-b signalling in these patients.…”

“…Recent studies from our lab indicate that TGF‐β acts as a potent tumour suppressor in sporadic cSCC where ~ 30% of cSCCs harbour either TGFBR1 or TGFBR2 mutations, leading to inactivation of canonical signalling 17 . Mutational alteration in TGF‐β signalling, 18 and reduction in canonical signalling activity correlates with markers of disease progression 17–19 . In contrast, mutations in TGFBR1 or TGFBR2 have not been found in RDEB cSCC, 20 indicative of potential tumour‐promoting canonical TGF‐β signalling in these patients.…”