Transcriptomic and immunohistochemical approaches identify HLA-G as a predictive biomarker of gestational choriocarcinoma resistance to monochemotherapy

Highlights

• Moles with post-curettage choriocarcinoma evolution and those with remission show similar transcriptomic profiles.

• HLA-G is under-expressed in monochemotherapy resistant gestational choriocarcinoma.

• Polychemosensitive and polychemoresistant choriocarcinoma show similar transcriptomic profiles.

Abstract

Objective

Using a transcriptional approach on tissue samples, we sought to identify predictive biomarkers of post molar malignant transformation, and of choriocarcinoma chemosensitivity to mono- (methotrexate or actinomycin D) or polychemotherapy [EMA(Etoposide, Methotrexate, Actinomycin D)-CO(Cyclophosphamide, Vincristine) and EMA-EP(Etoposide, Cisplatine)] regimens.

Methods

We studied the expression of a 760-gene panel (PanCancer Pathway) related to oncogenesis and immune tolerance in tissue samples of complete hydatidiform moles and gestational choriocarcinoma.

Results

We did not identify any differentially expressed gene between moles with post molar malignant transformation in choriocarcinoma (n = 14) and moles with remission (n = 20). In monochemoresistant choriocarcinoma (n = 34), four genes (HLA-G, COL27A1, IL1R2 and GLI3) had a significantly reduced expression and one (THEM4) had an increased expression [FDR (false discovery rate) adjusted p-value ≤ 0.05] when compared to monochemosensitive choriocarcinoma (n = 9). The proportion of trophoblast cells and the intensity of immunohistochemical HLA-G expression were reduced in monochemoresistant choriocarcinoma (p < 0.05). In polychemoresistant choriocarcinoma (n = 20) we did not identify differentially expressed genes with an FDR adjusted p-value ≤ 0.05 when compared to polychemosensitive choriocarcinoma (n = 15). Gene pathway analysis revealed a predicted activation of IFN ᵞ in monochemoresistant choriocarcinoma and inhibited IL2 and TNF in polychemoresistant choriocarcinoma. The main biological functions predicted to be altered in chemoresistant choriocarcinoma were related to immunological homeostasis and leukopoiesis.

Conclusion

HLA-G is a strong candidate gene to predict choriocarcinoma resistance to monochemotherapy and that further studies are required to implement its routine quantification in the decision process for the management of gestational choriocarcinoma.

Introduction

Gestational trophoblastic neoplasia (GTN) are epithelial proliferations developed from placental trophoblast [1]. Although the majority of patients can be cured when treated according to international standards, some of patients experience relapses and poor survivals, especially those with histology of choriocarcinoma or with disseminated diseases, mainly due to chemoresistance [2,3]. Except for rare GTN types such as placental site trophoblastic tumors and epithelioid trophoblastic tumors, which should be treated with surgical excision, the reference treatment for GTN is chemotherapy [4,5]. The choice of chemotherapy regimen is based on the FIGO (Fédération Internationale de Gynécologie Obstétrique) score, which is calculated with clinical, biological and radiological data. A score ≤ 6 indicates a low-risk of resistance to monochemotherapy, i.e. methotrexate or actinomycin D [5], while those with a score ≥7 are treated with polychemotherapy, the most described being EMA-CO (etoposide, methotrexate, actinomycin-D, cyclophosphamide and vincristine) [[4], [5], [6]]. Nevertheless, among low-risk patients, the incidence of resistance to methotrexate is still 22.5–50% [[7], [8], [9], [10]]. Moreover, long-term adverse effects observed with these regimens are significant, with increased risks of oral carcinomas, melanoma, meningioma, leukemia and early menopause after EMA-CO for example [11].

In the context of innate tolerance of trophoblast tissues and ubiquitous expression of immune check-points, such as PD-L1 in GTN tissue samples, the effectiveness of PD-L1 blockade with avelumab in patients resistant to methotrexate or EMA-CO is being assessed in an ongoing phase II trial (NCT03135769) [12,13]. The preliminary results suggested that up to 50% patients experienced disease remissions and hCG normalizations after resistance to methotrexate, with only few minor side effects, while the remaining patients had resistances to avelumab [14]. It raises the question of the deleterious role of first-line chemotherapy that could potentially lead to a depletion of the cellular anti-tumor immune response. Thus, it would be relevant to predict post molar malignant transformation early, as well as the risk of resistance to chemotherapy, in order to offer immunotherapy as a first-line treatment as way of improving survival while avoiding additional unnecessary chemotoxicity. So far, no predictive biomarkers of post molar choriocarcinoma transformation or chemoresistance have been identified.

Using a transcriptional approach on tissue samples, the present study aimed at identifying predictive biomarkers of malignant transformation of hydatidiform moles, and of choriocarcinoma chemosensitivity to mono or polychemotherapy regimens.