Transcriptional levels of KIFs in patients with HCC
Based on the Oncomine database, we compared the transcription levels of 45 molecules in 14 KIF subfamilies in 20 cancers with those in normal samples (Fig. 1). We found that 9 KIFs were differentially expressed in HCC; 8 of them (KIF2C, 4A, 10, 11, 14, 18B, 20A, and 23) were highly expressed and 1 (KIF22) was lowly expressed. Next, we selected the 8 highly expressed KIF factors for further analysis. In Wurmbach’s HCC data set [18], the mRNA expression levels of the 8 KIFs increased significantly. In Roessler’s HCC data set [19], the fold change in the mRNA expression of KIF2C, 4A, 14, 18B, and 20A were 2.69, 2.704, 2.406, 2.093, and 3.252, respectively, compared to normal samples. In Roessler’s other HCC dataset [19], KIF2C, 4A, and 20A mRNA expressions also increased considerably. In Chen’s HCC dataset [20], the fold change in the mRNA expression of KIF11 and KIF23 were 2.690 and 2.253, respectively (Table 1).
Table 1
The significant changes in KIF expression at the transcriptional level in hepatocellular carcinoma and liver tissues (Oncomine database)
| Fold change | P-value | t-test | Ref |
KIF2C | 3.462 | 4.20E-7 | 5.958 | Wurmbach [18] |
| 2.169 | 3.95E-48 | 17.795 | Roessler [19] |
| 2.867 | 5.84E-7 | 6.561 | Roessler [19] |
KIF4A | 4.704 | 1.88E-9 | 7.769 | Wurmbach [18] |
| 2.704 | 3.54E-62 | 22.006 | Roessler [19] |
| 2.665 | 4.05E-8 | 7.415 | Roessler [19] |
KIF10 | 3.123 | 4.48E-8 | 6.758 | Wurmbach [18] |
KIF11 | 3.846 | 1.84E-8 | 7.052 | Wurmbach [18] |
| 2.690 | 4.05E-12 | 7.504 | Chen [20] |
KIF14 | 5.344 | 9.34E-14 | 10.605 | Wurmbach [18] |
| 2.406 | 2.19E-8 | 7.893 | Roessler [19] |
KIF18B | 2.093 | 3.22E-8 | 7.182 | Roessler [19] |
| 2.680 | 6.23E-6 | 5.081 | Wurmbach [18] |
KIF20A | 6.336 | 8.38E-11 | 8.766 | Wurmbach [18] |
| 3.252 | 2.47E-68 | 24.329 | Roessler [19] |
| 2.711 | 5.62E-8 | 7.398 | Roessler [19] |
KIF23 | 2.253 | 3.93E-17 | 9.286 | Chen [20] |
| 2.143 | 2.17E-5 | 4.633 | Wurmbach [18] |
The relationship between the mRNA levels of 8 KIFs and clinicopathological parameters in HCC
Based on the GEPIA dataset, we compared the mRNA expression of 8 KIFs between HCC and healthy liver tissues and determined the correlation between these levels and the tumor stage. Our results showed that the expression levels of the 8 KIFs in HCC were higher than those in normal liver tissues (Fig. 2A, B), and there were significant differences in tumor staging (Fig. 2C).
Increased mRNA expression of 8 KIFs is associated with poor prognosis in HCC patients
We used Kaplan-Meier to further explore the prognostic significance of the 8 KIFs in HCC patients. Correlations between the mRNA levels of KIFs and OS, RFS, and PFS in 364, 316, and 370 cases of HCC, respectively, were analyzed. The Kaplan-Meier curve and log-rank test analysis showed that the elevated mRNA levels of the 8 KIFs were closely related to poor OS, poor RFS, and poor PFS (Fig. 3).
Function prediction and pathway information of 8 KIFs and their closely related neighboring genes in HCC
We used the cBioPortal online tool to analyze the interaction network relationship between 8 KIFs and HCC. As shown in Fig. 4A, KIFs changed in 107 (29.72%) of the 360 HCC patient samples, with two or more changes detected in almost half of the changed samples (53 samples) (Fig. 4A). We also analyzed the mRNA expression of KIFs (RNA Seq V2 RSEM) using the cBioPortal online tool and determined intercorrelations among the 8 KIFs using Pearson’s correction coefficient. The results showed significant positive correlations between the 8 KIFs (Fig. 4B). Next, we filtered the 50 neighboring genes most relevant to the 8 KIFs through the String database and constructed a network map. Per our findings, cell cycle-related genes, including CDK1, RACGAP1, PLK1, ECT2, CCNB1, CCNB2, CDC20, CCNA2, and CDC5L,were closely linked to changes in the 8 KIFs (Fig. 4C).
We then used DAVID and KEGG to predict GO enrichment analysis, including biological processes, cellular components, and molecular functions, and to determine the KEGG pathway map of these 58 genes. We found that GO: 000706 (mitosis), GO: 0000087 (M phase of the mitotic cell cycle), and GO: 0022402 (cell cycle process) were significantly regulated by changes in KIFs (Fig. 5A). GO: 0005819 (spindle), GO: 0015630 (microtubule cytoskeleton), GO: 0000793 (condensed chromosome), GO: 0003777 (microtubule motor activity), and GO: 0005524 (ATP binding) were also significantly controlled by these alterations in KIFs (Fig. 5B and 5C). KEGG analysis revealed 13 pathways related to changes in KIFs (Fig. 5D). Among these pathways, hsa04110: cell cycle, hsa04115: P53 signaling pathway, hsa04068: FoxO signaling pathway, hsa05203: viral carcinogenesis, hsa05161: Hepatitis B, hsa04390: Hippo signaling pathway, and hsa04152: AMPK signaling pathway reportedly participate in HCC occurrence and pathogenesis.
Finally, we used GSEA to analyze the pathway enrichment of the 8 KIFs in HCC to verify our results. Consistent with our earlier finding, the high expression of the 8 evaluated KIFs was most relevant to the cell cycle pathway in HCC. In addition, the high expression of these KIFS is involved in DNA replication, base excision repair, P53 signaling pathway, Notch signaling pathway, and more (Fig. 6).