Prognostic value and clinicopathologic characteristics of L1 cell adhesion molecule (L1CAM) in a large series of vulvar squamous cell carcinomas

Abstract

Background: Vulvar cancer treatment is mostly curative, but also has high morbidity rates. In a search for markers that can identify patients at risk of metastases, we investigated the prognostic value of L1-cell adhesion molecule (L1CAM) in large series of vulvar squamous cell carcinomas (VSCCs). L1CAM promotes cell motility and is an emerging prognostic factor for metastasis in many cancer subtypes.

Results: L1CAM expression was observed at the invasive front or in spray-patterned parts of 17% of the tumours. L1CAM-positive tumours expressed vimentin more often, but L1CAM expression was not associated with TP53 or CTNNB1 mutations. Five-year survival was worse for patients with L1CAM expression (overall survival 46.1% vs 63.6%, P=.014, disease specific survival 63.8% vs 80.0%, P=.018). Multivariate analysis indicates L1CAM expression as an independent prognostic marker (HR 2.9, 95% CI 1.10-7.68). An in vitro spheroid invasion assay showed decreased invasion of L1CAM-expressing VSCC spindle cells after treatment with L1CAM-neutralising antibodies.

Methods: Paraffin-embedded tumour tissue from two cohorts (N=103 and 245) of primary VSCCs were stained for L1CAM, vimentin and E-cadherin. Patients of the first cohort were tested for human papilloma virus infection and sequenced for TP53 and CTNNB1 (β-catenin) mutations. The expression of L1CAM was correlated to clinical characteristics and patient survival.

Conclusion: This is the first study to show high L1CAM-expression at the infiltrating margin of VSCC's. L1CAM-expressing VSCCs had a significantly worse prognosis compared to L1CAM-negative tumours. The highest expression was observed in spindle-shaped cells, where it might be correlated to their invasive capacity.

Keywords: L1 cell adhesion molecule; L1CAM; squamous cell carcinoma; survival; vulvar cancer.

Figure 1. L1CAM expression

Two vulvar squamous cell carcinomas with spindle cell morphology (A and B) and solid growth pattern (C and D) stained for keratin (A and C) and L1CAM (B and D). Arrowhead: nerve axon as an internal positive control.

Figure 2. Survival curves

Kaplan meier survival curves for the leiden cohort, n=103 A, B. and both cohorts combined, n=348 C, D. P-values for log-rank test.

Figure 3. Spheroid invasion assay

A. Spindle shaped cells highly express L1CAM, while L1CAM expression on cobble shaped cells is very low. B. Spindle and cobble cells form spheroids equally well and invade when embedded in a collagen matrix (C. and D.). Note that the invasion of the non-L1CAM expressing cobble shaped cells (C) is hardly affected by L1CAM neutralising antibodies, while spindle cell invasion can be strongly inhibited by the L1CAM neutralising antibodies (D)