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Molecular Mechanism of Forkhead Box M1 Inhibition by Thiostrepton in Breast Cancer Cells

October 1, 2019.


       Breast cancer is one of the most common cancers among women around the world. In 2012, there are 240,000 new cases of breast cancer and around 110,000 deaths in Southeast Asian, reported by World Health Organization: WHO [1]. According to the hospital based cancer registry of Thailand, the number of new patients with breast cancer is around 926 in 2018, and it is higher than it was in 2000 by 17%. The new cases of breast cancer are the highest number, compared to the other cancer types. In general, surgery, radiotherapy and chemotherapy including the combination of these treatments have been used for breast cancer therapy. In case of patients who have no expression of hormonal receptor (Oestrogen/Progesterone receptor negative: ER/PR-) or those who cannot be treated with targeted therapy (HER2/neu negative) probably caused drug resistance [2] and consequently resulted in 90% of clinical failure [3]. Therefore, the development of new treatment technique for breast cancer with high therapeutic efficiency, low toxicity and drug resistance avoid is still demanded.


       Anthracyclines (such as Doxorubicin and Epirubicin) had been widely used in cancer therapy, which has been known to cause the genotoxic to the cancer cells and lead to the cell death (apoptosis) [4, 5]. In case of cancer cells, the Forkhead box M1 (FOXM1) plays an important role in repairing damaged DNA, which is caused by chemotherapy [6]. FOXM1 belongs to the forkhead box transcription factor family, which is characterized by the forkhead box domain (FKH; also known as DNA binding domain). FKH is known to binds to the promoter motif of its downstream target gene [7, 8]. FOXM1 has been reported to play a crucial role in enhancing cellular progression in both stem cells and cancer. Various studies have revealed the data showing that upregulation of FOXM1 associated with various types of cancer progression, including breast cancer [9, 10]. In cancer metastasis and chemotherapy resistance study, there is a clear evidence pointing out that FOXM1 is a key protein in DNA damage repair, which can lead to the cancer chemotherapy resistance [11]. Several studies have shown that an inhibition of FOXM1 expression and activity leads to the dramatic decrease of cancer metastasis rate and increase the sensitivity of cancer cells to chemotherapy drugs [12, 13]. Upon the anthracycline chemotherapy treatment, FOXM1 is shown to be significantly degraded after the treatment in common breast cancer cells, via SUMO1-mediated ubiquitination and proteasome degradation [14-16]. Additionally, the non-degradable FOXM1 can lead to the higher DNA repair after chemotherapy, and increase the resistant to anthracycline [17]. Antibiotic thiazole compound produced by Streptomyces sp., kill breast cancer cells via inhibiting FOXM1. Previous studies showed that thiazole can inhibit the binding between FOXM1 and its targeted DNA, and consequently causes the influence on DNA repairing process. The thiazole is expectedly bound to binding domain of FOXM1 and its targeted DNA. Unfortunately, there are reported on some limitation of thiazole e.g. less soluble, poor stability and complicated synthesis. The new design and development of thiazole properties are needed. Therefore, the understanding at molecular level of mechanism of FOXM1-DNA complex inhibited by thiostreptonis focused in the present study. Moreover, the effect of thiostrepton on breast cancer cells is also studied. Both theoretical and experimental techniques are performed.


       In the present work, we applied physics knowledges to explain the molecular behaviors of complex biological system. Molecular dynamics (MD) simulation is a technique to visualize the physical movement of concerned atoms or molecules. The molecular motion is calculated based on Newton's second law. Originally, MD method is conceived more than 50 years ago in theoretical physics, but is widely applied these days mostly in biological, chemical and material systems, and could provide the comparable results with the experiments [18, 19]. In our study, the obtained results showed that the thiostrepton could induce stronger binding between the FOXM1 and its targeted DNA. The hydrogen bond lifetime between FOXM1 and targeted DNA of thiaostrepton binding to the FOXM1-DNA complex was significantly higher than the FOXM1-DNA complex without thiaostrepton binding. Moreover, the fluctuation of amino acid at binding domain was decreased when the thiaostrepton was bound to the FOXM1. The binding of thiaostrepton and FOXM1-DNA complex is shown in Figure 1. The in vitro investigation of thiaostrepton suppresses breast cancer cell growth was studied by cell survival assay (MMT assay). The results indicated that thiaostrepton significantly restricted cancer cell proliferation in a dose-dependent manner. MCF-7 Cell viability was decreased after being treated a dose of 0.47 mM for thiostrepton exposure for 24 hr. After 48-hour and 72-hour treatment, the cell viability was significantly reduced by lower than dose of 0.47 mM. In conclusion, the present study could provide the deep understanding at the atomistic level of the mechanism of FOXM1-DNA complex inhibited by thiaostrepton. The obtained information will be to the benefit of newly-designed drug in the future. The present project has been published in Oncology Report issue 42 and was chosen as the journal's cover. More details are as follows: Mesayamas Kongsema*, Sudtirak Wongkhieo, Mattaka Khongkow, Eric W.F. Lam, Phansiri Boonnoy, Wanwipa Vongsangnak and Jirasak Wong-ekkabut*, Molecular mechanism of Forkhead box M1 (FOXM1) inhibition by thiostrepton on breast cancer cells, Oncology Reports, Vol. 42, July 2019, pp. 953-962.




Fig. 1 Binding domain of thiaostrepton and FOXM1-DNA complex.





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Reported by


Assoc. Prof. Jirasak Wong-ekkabut *, Dr. Mesayamas Kongsema, Assoc. Prof. Wanwipa Vongsangnak and Miss Phansiri Boonnoy

Computational Biomodelling Laboratory for Agricultural Science and Technology (CBLAST), Dept. of Physics, Fac. of Science, Kasetsart University, Bangkok – 10900, Thailand