Boxplots representing L3MBTL4 mRNA expression level in breast tumors. (A) Comparison of L3MBTL4 expression according to its genomic status. L3MBTL4 expression level (log2 ratio) was lower in tumors with than without deletion (p = 5.05e-4). Red and green horizontal lines indicate thresholds (i.e. Basal tumors exhibited a normal mRNA expression (Figure 4B). However, the correlation between L3MBTL4 mRNA downregulation and gene loss was not simply a consequence of the proportion of basal tumors in the category "tumors without loss". Indeed, a similar proportion of basal tumors [26% (15/58) and 32% (52/162)] was observed in both "tumors with loss" and "tumors without loss" groups, respectively (Fisher test, p = 0.41). Moreover, downregulated L3MBTL4 expression was correlated with L3MBTL4 gene loss in basal tumors (p < 0.05).