Fig. 2.

Gene expression distribution in breast cancer samples. (A) The probability of the HER2 expression pattern having a normal distribution was determined by the Shapiro–Wilk normality test. The results revealed that HER2 expression in the breast cancer samples was not normally distributed. (B) The expression of HER2 in the 1,109 breast cancer samples is presented by the strength of HER2 expression (FPKM, x axis) and the cumulative distribution function (y axis), and the values are presented as open blue circles. A long-tailed distribution of HER2 expression was verified with tests, and a log-normal distribution (yellow color), an exponential distribution (red color), and a power-law distribution (purple color) and their expected values are labeled by different color lines. The P values were calculated by the poweRlaw package of R. (C) The Venn diagram shows the numbers of genes with expression fitting a long-tailed distribution (of 3,661 genes; average expression ≥ 1 FPKM; 6,006 plasma membrane protein-coding genes for breast cancer were considered); a log-normal distribution, an exponential distribution, or a power-law distribution. The number of genes and the corresponding percentage are labeled in each group in the Venn diagram.