Suboptimal cytoreduction in ovarian carcinoma is associated with molecular pathways characteristic of increased stromal activation

Abstract

Objective: Suboptimal cytoreductive surgery in advanced epithelial ovarian cancer (EOC) is associated with poor survival but it is unknown if poor outcome is due to the intrinsic biology of unresectable tumors or insufficient surgical effort resulting in residual tumor-sustaining clones. Our objective was to identify the potential molecular pathway(s) and cell type(s) that may be responsible for suboptimal surgical resection.

Methods: By comparing gene expression in optimally and suboptimally cytoreduced patients, we identified a gene network associated with suboptimal cytoreduction and explored the biological processes and cell types associated with this gene network.

Results: We show that primary tumors from suboptimally cytoreduced patients express molecular signatures that are typically present in a distinct molecular subtype of EOC characterized by increased stromal activation and lymphovascular invasion. Similar molecular pathways are present in EOC metastases, suggesting that primary tumors in suboptimally cytoreduced patients are biologically similar to metastatic tumors. We demonstrate that the suboptimal cytoreduction network genes are enriched in reactive tumor stroma cells rather than malignant tumor cells.

Conclusion: Our data suggest that the success of cytoreductive surgery is dictated by tumor biology, such as extensive stromal reaction and increased invasiveness, which may hinder surgical resection and ultimately lead to poor survival.

Keywords: Cancer-associated stroma; Cytoreductive surgery; Debulking; Desmoplasia; Epithelial–mesenchymal transition; Invasion; Metastasis; Ovarian cancer.

Fig. 1. Identification and validation of the suboptimal cytoreduction associated network (SCAN)

(A) Statistical analysis workflow chart. (B) Selected biomarkers with both differentially expressed genes and differential networks. (C) External validation of the network genes in the validation dataset (GSE9891). The top four genes with the lowest P values are highlighted in red. (D) Predicted Area Under the ROC Curve (AUC) for the SCAN genes in the validation dataset (GSE9891).

Fig. 2. The SCAN genes are highly enriched in the C1/mesenchymal molecular subtypes of EOC

Expression levels of the SCAN genes in (A) differentiated, immunoreactive, mesenchymal, and proliferative molecular subtypes in the TCGA dataset and (B) C1–C5 molecular subtypes in the Tothill dataset.

Fig. 3. EOCs characterized by lymphatic and venous invasion express higher levels of the SCAN genes

Relative expression levels of the SCAN genes in patient samples based on the presence or absence of (A) lymphatic invasion and (B) venous invasion. The number of samples in each category is indicated in parentheses.

Fig. 4. The SCAN genes are enriched in the cancer-associated stroma

(A) Relative expression levels of the SCAN genes in microdissected stromal and epithelial components in the normal ovary and in ovarian cancer. (B) Relative expression levels of the overall stromal marker VIM, reactive stroma marker ACTA2, and the SCAN genes in patient-matched omental metastases and primary tumors. The number of samples in each category is indicated in parentheses. (C) Representative images of sections of a recurrent serous ovarian tumor show COL11A1 expression in a subset of α-SMA-positive fibroblasts. Expression of COL11A1 was determined by in situ hybridization (ISH) with a COL11A1-specific probe. The presence of tumor stroma was determined by immunohistochemical (IHC) staining with α-SMA. The distribution of collagen and smooth muscle connective tissue was determined by Masson’s trichrome staining.