3.1. Survival outcomes and multivariate analysis
As shown in Fig. 1, increased expression of KPNA2 is significantly correlated with poor overall survival (Fig. 1A, P<0.001) and advanced pathological stage (Fig. 1B, P<0.001). In addition, KPNA2 expression in tumor samples is obviously lower than in normal (Fig. 1C). As shown in Table 1a, Univariate analysis using Cox regression revealed that in different tumor states, the influencing factors have different effects on the overall survival rate. In tumor stage(I-II), age (HR = 1.023, P<0.05) the expression of KPNA2 (HR = 1.705, P=0.000) are significantly associated with overall survival. In tumor stage (III-IV), the expression of KPNA2 (HR = 1.646, P=0.001) are significantly associated with overall survival. In multivariate analysis (Fig. 2), the down-regulated KPNA2 expression is independent prognostic factor of favorable prognosis.
3.2. Association between KPNA2 expression and clinicopathologic variables
The underlying mechanism of KPNA2 expression in cancer requires further study, hence we analyzed and correlated it with certain clinical aspects in cases of liver carcinoma. Cases with eligible clinical information were analyzed by R-3.5.3. As shown in Table 2, univariate analysis using logistic regression with KPNA2 expression as a categorical dependent variable revealed that increased expression of KPNA2 correlated significantly with the pathological stage (I vs II, p = 0.007; III vs I, p = 0.002), tumor status (T1 vs T2, p = 0.012; T1 vs T3, p = 0.006; T1-T2 vs T3-T4, p=0.033), and grade (II vs III, p = 0.011; I vs III, p = 0.028; I-II vs III-IV, p = 0.001).
3.3. Relationship between KPNA2 expression and tumor-infiltrating immune cells
Previous analyses suggest tumor-infiltrating lymphocytes as independent predictors of sentinel lymph node status and survival in cancer patients [16]. Therefore, we tried to find whether KPNA2 expression relates to immune infiltration in liver carcinoma. Among 374 liver carcinoma samples, samples with the top 1/3 and the lowest 1/3 KPNA2 expression were included into high expression group and low expression group, respectively. We use an established computational resource (CIBERSORT) to explore gene expression profiles of downloaded samples to infer the ratio of 22 types of immune cells in high and low KPNA2 expression groups. The results of CIBERSORT were exhibited in Fig. 3. The proportions of 22 subpopulations of immune cells were clearly rendered on it. As shown in Fig. 3A, main immune cells including B cells naive, B cells memory, T cells CD4 memory resting, T cells CD4 memory activated, T cells follicular helper, T cells regulatory (Tregs), T cells gamma delta, NK cells resting, monocytes, macrophages M0, macrophages M1, dendritic cells resting, mast cells resting, and neutrophils were affected by KPNA2 expression. Among them, B cells memory (p = 0.002), T cells CD4 memory activated (p < 0.001), T cells follicular helper (p < 0.001), Macrophages M0 (p < 0.001), Dendritic cells resting (p = 0.031), Neutrophils (p = 0.036) share a higher proportion in high expression group compared with low expression group. In contrast, the proportion of B cells naïve (p = 0.002), T cells CD4 memory resting (p = 0.002), NK cells resting (p = 0.023), Monocytes (p = 0.005), macrophages M1 (p = 0.002), Mast cells resting (p = 0.001), are apparently lower. In addition, correlation heatmap (Fig. 3B) revealed that the proportions of different TIICs subpopulations were weakly to moderately correlated.
“Correlation” module of GEPIA helped us to analyze the link between KPNA2 expression and gene markers of different types of tumor-infiltrating immune cells, including CD8+ T cells, T cells (general), B cells, neutrophils, Mast cells and DCs, as also different functional T cells, namely Th1, Th2, Tfh, Th17, Tregs, and exhausted T cells (Table 3). Results confirmed that KPNA2 expression is correlated with many marker sets of different immune cells in liver carcinoma. The gene markers effected by KPNA2 expression include CD8A, CD8B of CD8+ T cell, CD2, CD3E of T cell (general), KIR2DL3, KIR2DL4 of Natural killer cell, GATA3, STAT5A of Th2, STAT3 of Th17, CTLA4, LAG3 of T cell exhaustion, as well as HDC of Mast cells. Correlations were evaluated using Spearman correlation coefficient. Correlation results between KPNA2 and markers of B cells, Mast cells and T cells were similar to CIBERSORT. Thus, these findings indicate that KPNA2 may play a crucial role in regulating the abundance of B cells, Mast cells and T cells. Further studies need to be done to explore whether KPNA2 is a significant factor that relate to immune infiltration of Neutrophils.
Western blotting (Fig. 4) results showed that the expression of KPNA2 in liver cancer tissues was significantly lower than that in normal tissues adjacent to cancer.