Table 1. Change in hsp expression in response to low oxygen tension.

Hsp	Decrease of hsp expressionin 2% O2 (% of cell lines)	Mean decrease (%)	Increase of hsp expressionin 2% O2 (% of cell lines)	Mean increase (%)
90	50.0	19.5	38.9	13.9
70	44.4	27.3	44.4	15.0
60	50.0	20.4	33.3	16.8
40	61.1	18.3	16.7	16.8

Eighteen melanoma cell lines were cultured under identical conditions in 2% and 20% O₂. After five days the cell lines were harvested, stained with PE-conjugated hsp antibodies and protein expression assessed by flow cytometry. A Fluorescence Index was calculated (fold increase in mean fluorescence of the stained cells compared with the unstained cells) and was used as a comparative measure of protein expression.