Targeting Thymidylate Synthase Enhances the Chemosensitivity of Triple-Negative Breast Cancer Towards 5-FU-Based Combinatorial Therapy.

Nair Hariprasad Haritha,Maria Zajac-Kaye,Nesteena K Nestory,Balachandran S Vinod,Areekkara Nisthul Amrutha,Archana Krishna,Ruby John Anto,Sreekumar U Aiswarya,Vijayasteltar B Liju,Akbar Nawab,Mundanattu Swetha,Thomas Herlevich,Chittalakkottu Sadasivan,Nikhil Ponnoor Anto,Vinod Vijayakurup,Sankar Sundaram,Vijai V Alex,Maria V Guijarro,Smitha V Bava

doi:10.3389/fonc.2021.656804

Abstract

BackgroundThe ongoing treatment modalities for breast cancer (BC) primarily rely on the expression status of ER, PR and HER-2 receptors in BC tissues. Our strategy of chemosensitization provides new insights to counter chemoresistance, a major obstacle that limits the benefits of chemotherapy of mammary cancers.MethodsBy utilizing a murine breast cancer model employing NSG mice bearing orthotopic triple-negative breast cancer (TNBC) xenografts, we have evaluated the ability of phytochemical curcumin in chemosensitizing BC to 5-Fluorouracil (5-FU) chemotherapy and the differential modulations of cellular events in response to this strategy, independent of their receptor status.ResultsA significant synergistic antitumor potential was observed in the murine model with a sub-optimal dose treatment of 5-FU plus curcumin, as evaluated by a reduction in the tumor-related parameters. We authenticated the pivotal role of thymidylate synthase (TS) in regulating the 5-FU–curcumin synergism using the TNBC pre-clinical model. Our study also confirmed the pharmacological safety of this chemotherapeutic plus phytoactive combination using acute and chronic toxicity studies in Swiss albino mice. Subsequently, the molecular docking analysis of curcumin binding to TS demonstrated the affinity of curcumin towards the cofactor-binding site of TS, rather than the substrate-binding site, where 5-FU binds. Our concomitant in vivo and in silico evidence substantiates the superior therapeutic index of this combination.ConclusionThis is the first-ever pre-clinical study portraying TS as the critical target of combinatorial therapy for mammary carcinomas and therefore we recommend its clinical validation, especially in TNBC patients, who currently have limited therapeutic options.

Highlights

The highly heterogeneous nature of breast cancer (BC) is a major hurdle in developing single mode of treatment against diverse BC subtypes
In the acute toxicity study, the group of mice, which received 20 mg/kg 5-FU+ 25 mg/kg of curcumin and the group which received 20 mg/kg 5-FU+ 50 mg/kg of curcumin showed a slight increase in ALT level in comparison to other groups (Figure 1A), the changes fell in the normal reference range indicating safety of the regimen
We have demonstrated that 5μM curcumin is sufficient to down-regulate 5-FU-induced survival signals, which eventually leads to the upregulation of thymidylate synthase (TS) that develops chemoresistance in triple-negative breast cancer (TNBC) cells

Summary

Introduction

The highly heterogeneous nature of breast cancer (BC) is a major hurdle in developing single mode of treatment against diverse BC subtypes. Luminal tumors respond moderately well to hormonal interventions while human epidermal growth factor receptor-2 positive (HER-2+) tumors can effectively be managed using a diverse array of anti-HER-2 therapies. Despite this improvement in BC treatment modality, only 20% of triple-negative breast cancer (TNBC) and basal-like breast cancer (BLBC), devoid of estrogen (ER), progesterone (PR) and HER-2 receptors, respond well to standard chemotherapy, while the occurrence of these subtypes of BC is increasing in an alarming rate, worldwide [1,2,3]. Our strategy of chemosensitization provides new insights to counter chemoresistance, a major obstacle that limits the benefits of chemotherapy of mammary cancers

Methods

Results

Discussion

Conclusion