CHST4 Gene as a Potential Predictor of Clinical Outcome in Malignant Pleural Mesothelioma

Abstract

Malignant pleural mesothelioma (MPM) develops primarily from asbestos exposures and has a poor prognosis. In this study, The Cancer Genome Atlas was used to perform a comprehensive survival analysis, which identified the CHST4 gene as a potential predictor of favorable overall survival for patients with MPM. An enrichment analysis of favorable prognostic genes, including CHST4, showed immune-related ontological terms, whereas an analysis of unfavorable prognostic genes indicated cell-cycle-related terms. CHST4 mRNA expression in MPM was significantly correlated with Bindea immune-gene signatures. To validate the relationship between CHST4 expression and prognosis, we performed an immunohistochemical analysis of CHST4 protein expression in 23 surgical specimens from surgically treated patients with MPM who achieved macroscopic complete resection. The score calculated from the proportion and intensity staining was used to compare the intensity of CHST4 gene expression, which showed that CHST4 expression was stronger in patients with a better postoperative prognosis. The median overall postoperative survival was 107.8 months in the high-expression-score group and 38.0 months in the low-score group (p = 0.044, log-rank test). Survival after recurrence was also significantly improved by CHST4 expression. These results suggest that CHST4 is useful as a prognostic biomarker in MPM.

Keywords: CHST4; FFPE; immunohistochemistry; malignant pleural mesothelioma; prognostic factor.

Figure 1

Survival analysis across the entire transcriptome and new clusters unrelated to previous histological subtypes. (A) Consensus clustering using prognostic genes derived from screening by multiple testing with multivariate Cox regression analysis of gene expression in The Cancer Genome Atlas (TCGA) malignant pleural mesothelioma (MPM) dataset for OS. (B) Kaplan–Meier analysis using the TCGA MPM dataset was performed for two patient groups derived from consensus clustering. (C) The comparison between the conventional histological subtypes and new patient groups derived from the consensus clustering. The right-side table shows the patient numbers for each cluster and the conventional histological type.

Figure 2

Metascape functional analysis for unfavorable and favorable prognostic genes. The bar graph shows the top 20 clusters of enriched terms associated with unfavorable genes (A) and favorable genes (B). The color indicates the size of the p-value and the probability that the null hypothesis is rejected. The graph indicates the network of enriched terms associated with unfavorable genes (C) and favorable genes (D). The nodes are colored by cluster ID, and the nodes that share the same cluster ID are typically close to each other.

Figure 3

Relationship between CHST4 expression and Bindea immune−cell gene signatures. (A–K) The scatter plot shows the correlation between CHST4 expression and each immune−cell gene signature. Immune−cell gene signatures with significant correlations are indicated. (L) Heatmap depicting the relationship among clusters derived from comprehensive survival analysis, CHST4 expression, and the immune−cell gene signatures shown in (A–K) above. The samples are sorted by CHST4 expression.

Figure 4

Flow chart of patient selection. Of 51 patients who underwent surgery for malignant pleural mesothelioma at Nagoya University Hospital, 23 were included in this study, and the usability as a prognostic biomarker was validated by immunohistochemistry.

Figure 5

Images of immunohistochemistry performed on malignant pleural mesothelioma specimens. In case (A), which had a relatively good prognosis with a postoperative survival of 61.4 months, CHST4 immunoreactivity was localized in the perinuclear cytoplasm (indicated by arrowhead). (B) On the other hand, in the case with a poor prognosis with a postoperative survival of 7.6 months, no CHST4 expression was observed.

Figure 6

Kaplan–Meier survival curves for evaluating postoperative overall survival (OS) (A) and OS after recurrence (B) in two groups divided by the CHST4-TS. Patients with CHST4-TS ≥ 7 had significantly better survival (107.8 months vs. 38.0 months), and survival after recurrence also showed a similar trend (53.2 months vs. 14.0 months).