Figure 4. LPV sT is necessary and sufficient to transform MEFs.

A) Growth in low serum of MEFs expressing LPV LT and sT, on their own or in combination. Cells were plated and counted as described (Fig. 3B, materials and methods). While wt MEFs and LPV LT MEFs ceased to proliferate, MEFs expressing LPV sT -by itself on with LT- proliferated continuously. B) Soft agar formation induced by LPV products. LPV ER and sT were able to induce colonies in soft agar, but not LT. C) Box plots showing the size distribution of colonies for each cell type. Size was determined from images taken from each colony, as described in materials and methods, also Fig. 1D. Box plots showing the size distribution of colonies for each cell type were prepared using R programming. Each box plot is divided into four quartiles, the thick line in the middle of the box represents the median for the sample. Significance testing was performed by wilcox test using R programming. The size of colonies present in LPV LT expressing MEFs was not significantly different than that observed in wt MEFs (p value 0.36). MEFs expressing either LPV.ER, sT, or LT plus sT formed colonies in soft agar at a significantly larger rate (p value≪0.05). LPV sT expressing MEFs induced soft agar colonies of larger size than those formed by wt MEFs or LPV LT MEFs (p value= 0.0002), but the colonies were significantly smaller than those formed upon LPV.ER expression (p value= 0.02). Interestingly, co-expression of LPV LT and sT in trans resulted into significant increase in soft agar colonies with similar size to those found upon LPV.ER expression (p value= 0.622).