Natural products to enhance anti-tumor effects of trastuzumab and paclitaxel on the SKBR3, which is human breast cancer cell line.
Authors: Keskinkilic Merve , Altinay Fikri Mert , Pavlopoulou Athanasia , Yavuzsen Tugba , Gumustekin Mukaddes , Erdal Esra 
Published: June 2024

e13051 Background: Neoadjuvant chemotherapy (ChT) with targeted therapy is the standard treatment for human epidermal growth factor 2 (HER2)- positive breast cancer (BC). In this context, Trastuzumab (Tz) and ChT significantly improved the pathological complete response (pCR) rate. Tz and Paclitaxel (PTX) combination therapy is also one of the neoadjuvant treatments used in HER2+BC, and despite the effectiveness of this treatment, there is a critical need for innovative approaches and further research that will improve the neoadjuvant response rate. Addressing this, the NaturaProDB tool presents a novel avenue for predicting in silico natural non-toxic compounds with potential anti-cancer properties. Our study aims to investigate synergistic effect of natural products proposed by this database on theurapeutic action of Tz and PTX on BC. Methods: The NaturaProDB database was searched using the ‘Target Cancer’ option in order to identify those natural products with anti-BC potential and the corresponding experimentally verified target genes. Using this database, Biochanin A (BCA) and Delphinidin (Dp) were selected as natural compounds because they both commonly inhibit the MAPK signaling pathway. We used the HER2+ SKBR3 cell line to determine IC20, IC30 and IC50 doses for BCA, Dp, Tz, and PTX through MTT assay. Notably, all experiments were done after 72 hrs treatment of all compounds. Further, various combinations within different concentrations of natural products and Tz and PTX were tested to define additive anti-proliferative effects on SKBR3 cell line. Results: We first defined two natural products with drug-like properties, BCA and Dp, which have anti-proliferative effect on BC. Treatment of SKBR3 with increasing concentrations of BCA and Dp caused dose-dependent proliferation inhibition and IC50 dose of compounds were defined as 42,70uM and 40,70uM, respectively. In addition, IC20 dose of Tz was 2,8µM, while IC30 dose of PTX was 2,3nM.Then, we showed that combinations of increasing doses of Dp (from 30µM to 90 µM) with IC20 Tz caused significant dose-dependent cell death compared to the control group (p<0.0001). And the combinations of increasing doses of BCA (from 45µM to 360 µM) with IC20 Tz led similar significant results (p<0.0001). Conclusions: Herein, it is shown that combining natural compounds (Dp, BCA) with conventional treatments (PTX,Tz) predicted for the SKBR3 cell line can enhance the inhibitory effect on cell proliferation. This study is one of the rare first cell line studies in which the synergistic effect of BCA and Dp, which are natural compounds selected using the NaturaProDB database, were combined with ChT and Tz to show their synergistic effect, and these findings indicate that synergistic combination treatments acting through different pathways (MAPK signaling pathway) can be used in the treatment of HER2+ and TN BC. It opens avenues for further research.