FIG. 10.

Influence of HP1^Hsα, HP1^Hsβ, and HP1^Hsγ on oncogenic transformation in vitro (A and B) and in vivo (C) and determination of colony formation by the agarose-independent anchorage assay. (A) Cells overexpressing GFP-HP1^Hsα or GFP-HP1^Hsβ (A-1) or nontagged HP1^Hsα or HP1^Hsβ (A-2) have a lower number of colonies than the parental cells. Cells overexpressing HP1^Hsγ did not show any change in colony formation. (B) Cells with expression of mutant GFP-HP1^Hsα or GFP-HP1^Hsβ form a higher number of colonies than the parental cells. Cells expressing mutant GFP-HP1^Hsγ did not show any influence on colony formation. (C) Cells with or without overexpression of wild-type and mutant GFP-HP1^Hsα, GFP-HP1^Hsβ, or GFP-HP1^Hsγ were injected subcutaneously into mice. Tumor growth was measured starting at day 14 after inoculation. Note that tumors derived from cells overexpressing GFP-HP1^Hsα or GFP-HP1^Hsβ grow more slowly than those of the control, while those derived from cells expressing mutant GFP-HP1^Hsα or GFP-HP1^Hsβ grow faster. Tumors derived from cells overexpressing wild-type or mutant GFP-HP1^Hsγ did not show any change in growth compared to that for the control.