Combining carbon monoxide-releasing molecules with anti-VEGF therapy for triple-negative breast cancer therapy

Triple-negative breast cancer (TNBC) is defined by the lack of expression of the oestrogen and progesterone receptors and the overexpression of HER-2. Recently, carbon monoxide (CO) was found to behave as an important endogenous signalling molecule and interestingly, to suppress vascular endothelial growth factor receptor-2 (VEGFR2) and protein kinase B (AKT) phosphorylation. Given that anti-angiogenic drugs exist as one of the few available therapies against TNBC, CO-releasing molecules (CORMs) could be used as part of a combination therapy, in order to reduce cancerdriven angiogenesis. Therefore, the aim of this project was to study any potential antiangiogenic properties of four commercially available CORMs and after the selection and structural modification of one of them, new analogues would be synthesized and evaluated in vitro. The four commercially available CORMs were screened for cytotoxicity against TNBC, epithelial and endothelial cells and found to be moderately toxic. They were also shown to reduce the glycolytic metabolism of TNBC cells, decrease VEGF excretion from both TNBC cell lines tested and downregulate the expression of the cytoprotective enzyme haem oxygenase-1 (HO-1). They were finally reported to moderately inhibit the activation of VEGFR2 and other downstream proteins upon stimulation with VEGF and reduce the tube formation ability of endothelial cells. These results were crucial for the selection of one lead compound, which was subjected to structural modifications and 15 new analogues were produced. The new molecules showed a more favourable cytotoxicity profile, with two of them being selectively toxic against TNBC. All the 15 analogues retained the ability to reduce VEGF excretion from TNBC cells and two of them were chosen for further studies. These two complexes downregulated the expression of HO-1 at similar levels and reduced the phosphorylation of some VEGFR2 downstream proteins more than the parent compound. Finally, both CORMs decreased the tube formation activity of endothelial cells. In summary, two of the commercially available and two of the newly synthesized CORMs showed promising anti-angiogenic properties and should be pursued further, in order to identify a mechanism of action for these organometallic complexes

Aspects of carbon monoxide in form of CO-releasing molecules used in cancer treatment: More light on the way

Carbon monoxide (CO) has always been recognised as a toxic gas, due to its higher affinity for haemoglobin than oxygen. However, biological studies have revealed an intriguing role for CO as an endogenous signalling molecule, a gasotransmitter. CO is demonstrated to exertmany cellular activities including anti-inflammatory, antiapoptotic, and antiproliferative activities. In animal studies, CO gas administration can prevent tissues from hypoxia or ischemic-reperfusion injury. As a result, there are a plethora of reports dealing with the biological applications of CO and CO-releasing molecules (CORMs) in inflammatory and vascular diseases. CORMs have already been tested as a therapeutic agent in clinical trials. More recently, an increased interest has been drawn to CO’s potential use as an anticancer agent. In this review, we will aim to give an overview of the research focused on the role of COand CORMs in different types of cancer and expand to the recent development of the next generation CORMs for clinical application in cancer treatment

Repurposing old carbon monoxide-releasing molecules towards the anti-angiogenic therapy of triple-negative breast cancer

Triple-negative breast cancer (TNBC) is defined by the lack of expression of the oestrogen and progesterone receptors and HER-2. Recently, carbon monoxide (CO) was found to behave as an important endogenous signalling molecule and to suppress VEGF receptor-2 (VEGFR-2) and protein kinase B phosphorylation. Given that anti-angiogenic drugs exist as one of the few available targeted therapies against TNBC, the aim of this project was to study the effects of CO-releasing molecules (CORMs) on TNBC cell lines and the associated endothelial cells and characterise their anti-angiogenic properties that can be used for the reduction of cancer-driven angiogenesis. Four commercially available CORMs were screened for their cytotoxicity, their effects on cell metabolism, migration, VEGF expression, tube formation and VEGFR-2 activation. The most important result was the reduction in VEGF levels expressed by CORM-treated TNBC cells, along with the inhibition of phosphorylation of VEGFR2 and downstream proteins. The migration and tube formation ability of endothelial cells was also decreased by CORMs, justifying a potential re-purposing of old CORMs towards the anti-angiogenic therapy of TNBC. The additional favourable low cytotoxicity, reduction in the glycolysis levels and downregulation of haem oxygenase-1 in TNBC cells enhance the potential of CORMs against TNBC. In this study, CORM-2 remained the most effective CORM and we propose that CORM-2 may be pursued further as an additional agent in combination with existing anti-angiogenic therapies for a more successful targeting of malignant angiogenesis in TNBC

Virtual screening, SAR and discovery of 5-(indole-3-yl)-2-[(2-nitrophenyl)amino] [1,3,4]-oxadiazole as a novel Bcl-2 inhibitor

A new series of oxadiazoles were designed to act as inhibitors of the anti-apoptotic Bcl-2 protein. Virtual screening led to the discovery of new hits that interact with Bcl-2 at the BH3 binding pocket. Further study of the structure-activity relationship of the most active compound of the first series, compound 1, led to the discovery of a novel oxadiazole analogue, compound 16j, that was a more potent small molecule inhibitor of Bcl-2. 16j had good in vitro inhibitory activity with sub-micromolar IC50 values in a metastatic human breast cancer cell line (MDA-MB-231) and a human cervical cancer cell line (HeLa). The antitumour effect of 16j is concomitant with its ability to bind to Bcl-2 protein as shown by an enzyme linked immunosorbent assay (IC50 = 4.27 μM). Compound 16j has a great potential to develop into highly active anticancer agent

Anti-angiogenic drugs in cancer therapeutics: a review of the latest preclinical and clinical studies of anti-angiogenic agents with anticancer potential

Cancer is a group of diseases with significant morbidity and mortality. In cancer cells, where energy requirements are exceptionally high, angiogenesis, which is the sprouting of new blood vessels from pre-existing ones, is an important process for tumour survival and progression. Hence, extensive research in recent years focuses on the discovery of new anticancer drugs that target angiogenesis. Several methodologies have been developed preclinically, including the inhibition of pro-angiogenic factors and their receptors via micromolecular agents or monoclonal antibodies and the inhibition of other compensatory pathways beyond the traditional angiogenic ones. The purpose of the literature review is to present new anticancer drugs that target the process of angiogenesis and have been under preclinical or clinical investigation during the last five years. Many new anticancer drugs targeting angiogenesis are identified in the literature. The results of the in vitro and in vivo evaluation of these drugs show that, apart from inhibiting angiogenesis, they also affect cancer cell proliferation and tumour growth. Recent clinical studies show that these drugs increase the overall or disease-free survival of patients, even those with persistent, chemotherapy-resistant and metastatic types of cancer, although treatment-related side effects are not uncommon. Drugs that target the process of angiogenesis are likely to be the future of anticancer therapy, especially in cases where more traditional treatments do not produce the desired results and where combination regimens of anti-angiogenic agents with standard chemotherapeutics increase patient survival

Aspects of Carbon Monoxide in Form of CO-Releasing Molecules Used in Cancer Treatment: More Light on the Way

Carbon monoxide (CO) has always been recognised as a toxic gas, due to its higher affinity for haemoglobin than oxygen. However, biological studies have revealed an intriguing role for CO as an endogenous signalling molecule, a gasotransmitter. CO is demonstrated to exert many cellular activities including anti-inflammatory, antiapoptotic, and antiproliferative activities. In animal studies, CO gas administration can prevent tissues from hypoxia or ischemic-reperfusion injury. As a result, there are a plethora of reports dealing with the biological applications of CO and CO-releasing molecules (CORMs) in inflammatory and vascular diseases. CORMs have already been tested as a therapeutic agent in clinical trials. More recently, an increased interest has been drawn to CO's potential use as an anticancer agent. In this review, we will aim to give an overview of the research focused on the role of CO and CORMs in different types of cancer and expand to the recent development of the next generation CORMs for clinical application in cancer treatment

Structural modifications on CORM-3 lead to enhanced anti-angiogenic properties against triple-negative breast cancer cells

Purpose: Carbon monoxide-releasing molecules (CORMs) are a special class of organometallic complexes that have been reported to offer beneficial effects against different conditions including several subtypes of cancer. Especially for the aggressive and poorly treated triple-negative breast cancer (TNBC), early CORMs have been shown to diminish malignant angiogenesis and may be considered as an alternative approach. So, this study aimed at testing novel CORM molecules against angiogenesis in TNBC seeking potent drug candidates for new therapies. Methods: Based on previous studies, CORM-3 was chosen as the lead compound and a group of 15 new ruthenium-based CORMs were synthesized and subsequently evaluated in vitro for potential anti-angiogenic properties. Results: A similar anti-angiogenic behaviour to the lead complex was observed and a new CORM, complex 4, emerged as a promising agent from this study. Specifically, this complex offered better inhibition of the activation of VEGFR2 and other downstream proteins of vascular endothelial cells. Complex 4 also retained the ability of the parent molecule to reduce the upregulated VEGF expression from TNBC cells and inhibit endothelial cell migration and new vessel formation. The lack of significant cytotoxicity and the downregulating activity over the cytoprotective enzyme haem oxygenase-1 (HO-1) in cancer cells may also favour CORMs against this poorly treated subtype of breast cancer. Conclusions: Since the anti-angiogenic approach is one of the few available targeted strategies against TNBC, both CORM-3 and the new complex 4 should be considered for further research as combination agents with existing anti-angiogenic drugs for a more effective treatment of malignant angiogenesis in TNBC