Clinically proven markers of metastasis predict metastatic spread of human melanoma cells engrafted in scid mice

Abstract

Metastasis formation is a complex process and as such can only be modelled in vivo. As markers indicating metastatic spread in syngenic mouse models differ significantly from those in man, this study aimed to develop a human melanoma xenograft mouse model that reflects the clinical situation. Six human melanoma cell lines (LOX, MV3, FEMX-1, G361, MeWo and UISO-Mel6) were xenografted into severe combined immunodeficient mice and tumour growth, metastatic behaviour and number of lung metastases were assessed. Tumours and metastases were analysed for HPA binding and expression of CEACAM-1 and L1, all markers indicative of metastasis in clinical studies. Development of primary tumour nodules ranged from 3 weeks (MV3) to 3 months (MeWo). Whereas G361 and FEMX-1 rarely formed lung metastases, MeWo, MV3 and LOX were moderately and UISO-Mel6 was highly metastatic. Similar to clinical studies, HPA, CEACAM1 and L1 indicated metastatic spread in the xenograft melanoma model, but were not all simultaneously expressed in all cell lines. Considering the strongest expression of one marker combined with an absent or low expression of the other two markers, we conclude that LOX is the cell line of choice for analyses of the functional role of HPA-binding glycoconjugates, UISO-Mel6 is ideally suited to study CEACAM1 function in melanoma spread and L1 function can best be modelled using MeWo.

Figure 1

H&E staining of UISO-Mel6 lung metastasis. UISO-Mel6 developed lung metastases of enormous size (up to 900 cells in a cross-section). (A) Metastasis in the pulmonary artery; (B) bronchial branch; (C) extravasal melanoma cells. Bar represents 100 μm.

Figure 2

H&E staining of FEMX-1 lung metastasis. FEMX-1 developed only single-cell micrometastasis (arrow). Bar represents 100 μm.

Figure 3

L1 immunohistochemistry of MeWo lung metastasis. Melanoma cells show intense (+++) L1 immunoreactivity, and even small metastases in the peripheral lung tissue are easy to detect (arrows). (A) metastasis in the pulmonary artery. Bar represents 100 μm.

Figure 4

Comparative HPA lectinhistochemistry using two different methodological approaches. Primary tumours of the cell line LOX showed intense (+++) membranous HPA labelling with both methods: (A) bHPA using biotinylated HPA and (B) iHPA using native HPA and an anti-HPA antibody. Bar represents 100 μm.

Figure 5

CEACAM1 immunohistochemistry of an UISO-Mel6 lung metastasis. The cells in the metastatic nodules exhibit intense (+++) CEACAM1 immunoreactivity. Melanoma cells have invaded the lung tissue starting from the (A) pulmonary artery. (B) Bronchial branch. Bar represents 100 μm.