TMOD3 expression in ovarian cancer
First, the GEO database showed that the mRNA expression levels of TMOD3 were elevated in microarray datasets GSE51088 and GSE66957 (Figure 1A,B). TMOD3 was also highly expressed in ovarian cancer compared to normal ovarian tissues by the TNMplot web tool (Figure 1C). Analysis of CPTAC data by the UALCAN web tool showed that the protein level of TMOD3 was also significantly higher in ovarian cancer than in normal ovarian tissues (Figure 1D). Besides, the GEO dataset GSE53963 showed that TMOD3 expression was significantly higher in ovarian cancers with grade 4 than in those with grades 2 and 3 (Figure 1E), and the GSE23554 dataset showed that TMOD3 levels were higher in patients with stage 3 ovarian cancer than in those with stages 1 and 2 (Figure 1F). In addition, the GSE131978 dataset showed that TMOD3 expression was also significantly higher in ovarian cancer tissues with metastasis than in those without metastasis (Figure 1G). These results suggest that TMOD3 may influence ovarian cancer progression.
Effects of platinum on TMOD3 expression in ovarian cancer
Chemotherapy is an important factor influencing ovarian cancer progression33. To investigate whether TMOD3 affects ovarian cancer progression by influencing chemotherapy, this study first observed whether TMOD3 expression was altered in ovarian cancer when treated with chemotherapeutic drugs. GSE47856 dataset showed that the expression level of TMOD3 decreased after being treated with cisplatin in the ovarian cancer CH1 cell line (Figure 2A). The GSE49577 dataset showed that TMOD3 mRNA expression was lower in ovarian cancer xenograft mice treated with carboplatin than untreated ones (Figure 2B). In addition, the GSE63885 dataset also showed that TMOD3 expression was significantly reduced after platinum-based chemotherapy in ovarian cancer patients who were highly sensitive to platinum compared to ovarian cancer patients who were not treated with chemotherapy, but there was no difference in ovarian cancer patients who were moderately sensitive to platinum (Figure 2C). The above results suggest that TMOD3 is a possible target of platinum.
TMOD3 expression in platinum-sensitive or resistant ovarian cancer
Based on the above results, this study hypothesized that high expression of TMOD3 in ovarian cancer might affect ovarian cancer progression by regulating platinum resistance. Therefore, this study first examined TMOD3 expression in drug-resistant cell lines or patient cancer tissues by multiple GEO datasets. Both GSE15372 and GSE33482 datasets showed that TMOD3 expression in cisplatin-resistant ovarian cancer cell line a2780 was significantly higher than that in the cisplatin-sensitive group (Figure 3A,B). The GSE45553 dataset showed that TMOD3 expression in cisplatin-resistant ovarian cancer spheroid expression was significantly higher than that of the cisplatin-sensitive group (Figure 3C). Finally, a comprehensive analysis of TCGA and GEO ovarian cancer chemotherapy patients using the ROC plotter revealed that the expression of TMOD3 was significantly higher in ovarian cancer patients with platinum resistance than with platinum-sensitive (Figure 3D). Moreover, the ROC curve showed TMOD3 as a marker for determining platinum resistance in ovarian cancer (Figure 3E). The above results suggest that high expression of TMOD3 may play an essential role in platinum resistance in ovarian cancer.
The effect of TMOD3 expression on ovarian cancer patient survival rate
Prognostic analysis of TCGA ovarian cancer patients by KM-plotter tool revealed that high expression of TMOD3 mRNA was significantly associated with low OS and PFS in total patients or patients with platinum treatment (Figure 4). Interestingly, PFS in patients with platinum treatment was more significant than total patients (Figure 4D). Because PFS is a better indicator of treatment outcomes than OS, the prognostic analysis further demonstrates the critical role of TMOD3 in patients with platinum-based chemotherapy for ovarian cancer.
mRNA-miRNA analysis of TMOD3 in ovarian cancer
Post-transcriptional regulation mediated by microRNAs is an important mechanism affecting gene expression. The function of a gene can be predicted based on the function of microRNAs targeting it34. To explore the possible mechanism of elevated TMOD3 expression in ovarian cancer, twenty-one microRNAs targeting TMOD3 were identified by TargetScan prediction. Their correlation with TMOD3 was also validated in TCGA ovarian cancer samples (Figure 5A). All of them have been shown to mediate tumor chemoresistance, and the majority (17/21) were shown to associate with cisplatin resistance in ovarian cancer35,36,37,38,39,40,41,42,43,44,45,46,47,48, except hsa-miR-301a-3p, hsa-miR -301b-3p, hsa-miR-365a-5p, and hsa-miR-365b-5p. In addition, analysis of the TCGA ovarian cancer samples revealed that both hsa-miR-454-3p and hsa-miR-133a-3p were most significantly negatively correlated with TMOD3 expression (Figure 5A-C). Furthermore, hsa-miR-133a-3p was found to be lowly expressed in cisplatin-resistant ovarian cancers by Linkedomics analysis (Figure 5E), while there was no significance in hsa-miR-454-3p (Figure 5D). Therefore, it is possible that post-transcriptional regulation mediated by microRNAs, especially hsa-miR-133a-3p, is responsible for the high expression of TMOD3 in cisplatin-resistant ovarian cancer.
Relationship between TMOD3 expression and immune infiltration in ovarian cancer
Immunotherapy is a novel and promising therapeutic strategy compared to chemotherapy and surgery. About 50% of ovarian cancer patients have spontaneous multiple immune cell infiltration49,50. Moreover, immunotherapy for ovarian cancer patients with chemoresistance is of interest. For example, the Programmed cell death 1 ligand 1 (PD-L1) inhibitor Durvalumab, in combination with the PARP inhibitor Olaparib, has shown good therapeutic effects in ovarian cancer patients with platinum-resistance51. The HPA dataset showed that TMOD3 was widely distributed in various immune cells (Figure 6A,B), implying TMOD3 plays an important role in the immune cells. Therefore, this study investigated the correlation between TMOD3 and ovarian cancer immune infiltration using TIMER. TMOD3 was negatively correlated with tumor purity (Figure 6C). This suggests that many other cells infiltrate ovarian cancer tissue and that TMOD3 could potentially influence ovarian cancer through these infiltrated cells. Indeed, the results further showed that TMOD3 expression was positively correlated with B lymphocytes, CD8+ T cells, neutrophils, and dendritic cells, but not with CD4+ T cells and macrophages (Figure 6D-I). This study further investigated the relationship between TMOD3 expression and immunomodulators or chemokines in ovarian cancer. It found that TMOD3 expression was significantly correlated with various immunomodulators (Figure 7A), including well-established immune checkpoints such as Programmed Death 1 (PD1), PD-L1 (CD274), and Cytotoxic T-Lymphocyte Antigen 4 (CTLA4) (Figure 7B-D). These results suggest that TMOD3 may play an important role in ovarian cancer immune infiltration.
TMOD3 coexpression networks in ovarian cancer
This study then explored the potential mechanisms of TMOD3 in the involvement of ovarian cancer. First, this study constructed the coexpression network of TMOD3 in ovarian cancer. A total of 4774 genes were significantly associated with TMOD3 in the TCGA ovarian cancer samples revealed by LinkedOmics. The heat map showed the TOP50 genes positively or negatively associated with TMOD3 (Figure 8A,B). Next, this study screened 295 genes interacting with TMOD3 using STRING. After overlapping 4774 genes significantly associated with TMOD3 and 295 genes interacting with TMOD3, 76 genes were screened (Figure 8C). Functional enrichment analysis of these 76 genes showed that actin cytoskeleton and focal adhesion were the most enriched (Figure 8D). KEGG pathway enrichment analysis revealed that proteoglycans in cancer were the most enriched (Figure 8E).
Small molecule therapeutics
Correlations between TMOD3 and potential drugs or small molecules were analyzed using the CTD database. A total of eight drugs were identified to have potential inhibitory effects on TMOD3 (Figure 9A), including acetaminophen, aristolochic acid I, bufalin, doxorubicin, folic acid, haloperidol, T-2 toxin, and Tetrachlorodibenzodioxin (Figure 9B-I). The molecular structures of the identified drugs were determined by the PubChem database. These drugs provide clues to overcoming the process of drug resistance in ovarian cancer mediated by TMOD3 overexpression.

Figure 1: mRNA and protein expression levels of TMOD3 in multiple ovarian cancer datasets. (A) Analysis of mRNA expression of TMOD3 in normal ovarian tissues (n = 20) and ovarian cancer (n = 152) by GSE51088 dataset. (B) Analysis of mRNA expression of TMOD3 in normal ovarian tissues (n = 12) and ovarian cancer (n = 57) by GSE66957 dataset. (C) Analysis of mRNA expression of TMOD3 in normal ovarian tissue (n = 133) and ovarian cancer (n = 374) by TNM plotter tool. (D) Analysis of protein expression of TMOD3 in normal ovarian tissue (n = 25) and ovarian cancer (n = 100) in CPTAC data by UALCAN tool. (E) Analysis of mRNA expression of TMOD3 in ovarian cancer of grade 2 and 3 (n = 94) and ovarian cancer of grade 4 (n = 80) by GSE53963 dataset. (F) Analysis of TMOD3 mRNA expression in ovarian cancer of stage 1 and 2 (n = 10) and ovarian cancer of stage 3 (n = 18) by GSE23554 dataset. Enter text here. (G) Analysis of TMOD3 mRNA expression in ovarian cancer with or without metastasis by the GSE131978 dataset. Data are represented as mean ± SEM. Please click here to view a larger version of this figure.

Figure 2: TMOD3 mRNA expression levels in ovarian cancer cell lines, transplanted tumors, and patients after platinum drug treatment. (A) Analysis of TMOD3 mRNA expression in cisplatin-treated (n = 3) and untreated CH1 (n = 3) ovarian cancer cell lines by the GSE47856 dataset. (B) Analysis of TMOD3 mRNA expression in cisplatin-treated (n = 12) and untreated TMOD3 mRNA expression in CH1 (n = 19) ovarian cancer transplants. (C) Analysis of TMOD3 mRNA expression in cisplatin-treated ovarian cancer patients with highly sensitive (HS, n = 13) and moderately sensitive to cisplatin (n = 28), as well as in patients without cisplatin treatment (n = 26). Data are represented as mean ± SEM. *compared with untreated, P < 0.05. Please click here to view a larger version of this figure.

Figure 3: TMOD3 mRNA expression levels in platinum-sensitive and platinum-resistant ovarian cancer cell lines or patients. (A,B) TMOD3 mRNA expression levels in cisplatin-sensitive and cisplatin-resistant A2780 cell lines were analyzed by the GSE15372 dataset (A) and GSE33482 dataset (B). (C) TMOD3 mRNA expression levels in cisplatin-sensitive and cisplatin-resistant ovarian cancer spheroid were analyzed by the GSE45553 dataset. (D,E) TMOD3 mRNA expression levels in platinum-sensitive and platinum-resistant ovarian cancer patients were analyzed by the ROC plotter tool (D), and TMOD3 was identified as a marker for determining platinum resistance by ROC curves (E). Data are represented as mean ± SEM. Please click here to view a larger version of this figure.

Figure 4: Correlation analysis of TMOD3 mRNA expression levels with OS and PFS of ovarian cancer patients. (A,B) Correlation analysis of TMOD3 mRNA expression levels with OS in all TCGA ovarian cancer patients (A) or patients receiving platinum-based chemotherapy (B). (C,D) Correlation analysis of TMOD3 mRNA expression levels with PFS in all TCGA ovarian cancer patients (C) or patients receiving platinum-based chemotherapy (D). Please click here to view a larger version of this figure.

Figure 5: Determination of relationships between TMOD3 and drug resistance by mRNA-microRNA interaction analysis. (A) Prediction of miRNAs targeting TMOD3. Line color represents the TargetScan Context++ score percentile, and node color represents the correlation strength between this miRNA and TMOD3 in the TCGA ovarian cancer dataset. (B,C) Correlation between TMOD3 mRNA expression levels and hsa-miR454-3p (B) and hsa-miR133a-3p (C) in TCGA ovarian cancer samples. (D,E) Expression of hsa-miR454-3p (D) and hsa-miR133a-3p (E) in cisplatin sensitive and resistant ovarian cancer in TCGA ovarian cancer samples. Data are represented as mean ± SEM. Please click here to view a larger version of this figure.

Figure 6: Correlation of TMOD3 mRNA expression levels with immune cell infiltration in ovarian cancer. (A,B) TMOD3 mRNA expression levels of immune cells in HPA dataset (A) and Monaco dataset (B). (C-I) Correlation of TMOD3 mRNA expression levels with tumor purity in TCGA ovarian cancer (C), B lymphocytes (D), CD4+ T cells (E), CD8+ T cells (F), macrophages (G), neutrophils (H), and dendritic cell (I) infiltration. Please click here to view a larger version of this figure.

Figure 7: Correlation analysis of TMOD3 mRNA expression levels with immunoregulatory factors in ovarian cancer patients. (A) The heat map of correlation between TMOD3 mRNA expression and immunoregulators in TCGA ovarian cancer, including immune inhibitors, immunostimulators, MHCs, chemokines, and receptors. (B-D) Correlation analysis of TMOD3 mRNA expression levels with immune checkpoints such as PD1 (B), PD-L1 (CD274) (C), and CTLA4 (D) in TCGA ovarian cancer samples. Please click here to view a larger version of this figure.

Figure 8: TMOD3 coexpression networks in ovarian cancer. (A,B) Heat maps showing the top 50 genes positively (A) and negatively (B) correlated with TMOD3 in TCGA ovarian cancer datasets using LinkedOmics. Red and blue represent positively and negatively correlated genes, respectively. (C) Venn diagram of 295 genes interacted with TMOD3, and the 4774 genes correlated with TMOD3 in TCGA ovarian cancer. (D) Functional enrichment analysis of 76 overlapping genes. The bubble plot demonstrated the top 5 elements significantly enriched in BP, CC, and MF. (E) The TOP10 pathways of KEGG pathway enrichment analysis. Please click here to view a larger version of this figure.

Figure 9: Prediction of potential drugs or small Molecules targeting TMOD3. (A) Prediction of potential drugs that target TMOD3 using CTD database, with red representing drug could inhibit TMOD3. (B-H) PubChem database reveals the molecular structures of eight targeted drugs. (B) Acetaminophen, (C) aristolochic acid I, (D) bufalin, (E) Doxorubicin, (F) Folic Acid, (G) Haloperidol, (H) T-2 Toxin. (I) Tetrachlorodibenzodioxin. Please click here to view a larger version of this figure.
Supplementary Figure 1: Methods for analyzing mRNA and protein expression levels of TMOD3 in multiple ovarian cancer datasets. (A) Analysis of TMOD3 expression using the GEO database. (B) Further analysis of data extracted from the GEO database using statistics and graphing software. (C) Analysis of TMOD3 expression using the TNMplot. (D) Analysis of protein expression using the UALCAN. Please click here to download this File.
Supplementary Figure 2: Prognostic analysis using KM-plotter. Please click here to download this File.
Supplementary Figure 3: ROC curves analysis using ROC plotter. Please click here to download this File.
Supplementary Figure 4: Methods for mRNA-miRNA analysis. (A) Prediction of miRNAs target TMOD3 using TargetScan. (B) Correlation analysis of TMOD3 with miRNAs using cBioportal. (C) Visualization of correlation analysis using Cytoscape. (D) Analysis of miRNAs expression using LinkedOmics. Please click here to download this File.
Supplementary Figure 5: Methods for immuno-infiltration analysis. (A) Analysis of TMOD3 distribution in various immune cells. (B) Correlation analysis of TMOD3 with immune infiltration using cBioportal. (C) Correlation analysis of TMOD3 with immunomodulators using TISIDB. Please click here to download this File.
Supplementary Figure 6: Prediction of genes interacted with TMOD3 using STRING. Please click here to download this File.
Supplementary Figure 7: Functional annotation using DAVID. Please click here to download this File.
Supplementary Figure 8: Prediction of drugs target TMOD3 using CTD database. Please click here to download this File.
Supplementary Figure 9: Analysis of the molecular structure of the drugs using PubChem database. Please click here to download this File.