Substitution of aspartic acid with glutamic acid at position 67 of the BRCA1 RING domain retains ubiquitin ligase activity and zinc(II) binding with a reduced transition temperature

Development and future prospects of selective organometallic compounds as anticancer drug candidates exhibiting novel modes of action

Organometallic complexes have widely been used for the treatment of various diseases viz., malaria, arthritis, syphilis, pernicious anemia, tuberculosis and particular in cancers. Recent decades have witnessed an upsurging interest in the application of organometallic compounds to treat various phenotypes of cancers with multiple etiologies. The unique and exceptional properties of organometallic compounds, intermediate between classical inorganic and organic materials provide new insight in the progress of inorganic medicinal chemistry. Herein, we have selectively focused on various organometallic sandwich and half-sandwich complexes of ruthenium (Ru), titanium (Ti), gold (Au) and iron (Fe) exhibiting promising activity towards a panel of cancer cell lines and resistant cancer cell lines. These complexes exhibit novel mechanisms of drug action through incorporation of outer-sphere recognition of molecular targets and controlled activation features based on ligand substitution along with monometallic and heterometallic redox processes. Furthermore, they are usually found to be uncharged or neutral possessing metals in a low oxidation state, exhibit kinetic stability, relative lipophilicity and are amenable to a host of various chemical transformations. This review mainly sheds light on the successful advancement of organometallic complexes as anticancer drug aspirants in relation to their versatile structural chemistry and innovative mechanisms of action targeting nucleic acids, several enzymes viz; thioredoxin reductases (Thrx), EGFR, transferrin, cathepsin B, topoisomerases etc.

Lymphangioleiomyomatosis: a case report and review of diagnosis and treatment

Lymphangioleiomyomatosis (LAM) is a rare disease that generally affects young women and involves the abnormal proliferation of smooth muscle-like cells (LAM cells) in the lungs (pulmonary LAM) and extrapulmonary sites (extrapulmonary LAM). This disease is rare in males. It is hard to distinguish between lung cancer and pulmonary LAM, especially during early stages. Herein, we present a case of a 66-year-old man with a small nodule in the right upper lobe that was first diagnosed as a lung malignancy using a chest CT scan. After a wedge dissection, a pathologist performed a histologic and immunohistochemical examination, and a diagnosis of pulmonary LAM was made. We further performed a 518-gene panel analysis using next-generation sequencing, and only three genes, BARD1, BLM, and BRCA2, were found to have mutations. We also provide a summary of the diagnosis and treatment of this disease.

On human disease-causing amino acid variants: statistical study of sequence and structural patterns

Statistical analysis was carried out on large set of naturally occurring human amino acid variations, and it was demonstrated that there is a preference for some amino acid substitutions to be associated with diseases. At an amino acid sequence level, it was shown that the disease-causing variants frequently involve drastic changes in amino acid physicochemical properties of proteins such as charge, hydrophobicity, and geometry. Structural analysis of variants involved in diseases and being frequently observed in human population showed similar trends: disease-causing variants tend to cause more changes in hydrogen bond network and salt bridges as compared with harmless amino acid mutations. Analysis of thermodynamics data reported in the literature, both experimental and computational, indicated that disease-causing variants tend to destabilize proteins and their interactions, which prompted us to investigate the effects of amino acid mutations on large databases of experimentally measured energy changes in unrelated proteins. Although the experimental datasets were linked neither to diseases nor exclusory to human proteins, the observed trends were the same: amino acid mutations tend to destabilize proteins and their interactions. Having in mind that structural and thermodynamics properties are interrelated, it is pointed out that any large change in any of them is anticipated to cause a disease.

Cellular responses of BRCA1-defective and triple-negative breast cancer cells and in vitro BRCA1 interactions induced by metallo-intercalator ruthenium(II) complexes containing chloro-substituted phenylazopyridine

BACKGROUND

Triple-negative breast cancer (TNBC) is defined by the absence of expression of estrogen receptor, progesterone receptor and human epidermal growth factor receptor 2. Breast cancers with a BRCA1 mutation are also frequently triple-negative. Currently, there is a lack of effective therapies and known specific molecular targets for this aggressive breast cancer subtype. To address this concern, we have explored the cellular responses of BRCA1-defective and triple-negative breast cancer cells, and in vitro BRCA1 interactions induced by the ruthenium(II) complexes containing the bidentate ligand, 5-chloro-2-(phenylazo)pyridine.

METHODS

Triple-negative MDA-MB-231, BRCA1-defective HCC1937 and BRCA1-competent MCF-7 breast cancer cell lines were treated with ruthenium(II) complexes. The cytoxoxicity of ruthenium-induced breast cancer cells was evaluated by a real time cellular analyzer (RTCA). Cellular uptake of ruthenium complexes was determined by ICP-MS. Cell cycle progression and apoptosis were assessed using propidium iodide and Annexin V flow cytometry. The N-terminal BRCA1 RING protein was used for conformational and functional studies using circular dichroism and in vitro ubiquitination.

RESULTS

HCC1937 cells were significantly more sensitive to the ruthenium complexes than the MDA-MB-231 and MCF-7 cells. Treatment demonstrated a higher degree of cytotoxicity than cisplatin against all three cell lines. Most ruthenium atoms were retained in the nuclear compartment, particularly in HCC1937 cells, after 24 h of incubation, and produced a significant block at the G2/M phase. An increased induction of apoptotic cells as well as an upregulation of p53 mRNA was observed in all tested breast cancer cells. It was of interest that BRCA1 mRNA and replication of BRCA1-defective cells were downregulated. Changes in the conformation and binding constants of ruthenium-BRCA1 adducts were observed, causing inactivation of the RING heterodimer BRCA1/BARD1-mediated E3 ubiquitin ligase activity.

CONCLUSIONS

This study has revealed the ability of ruthenium complexes to inhibit cell proliferation, induce cell cycle progression and apoptosis. Ruthenium treatment upregulated the marker genes involved in apoptosis and cell cycle progression while it downregulated BRCA1 mRNA and replication of HCC1937 cells. Our results could provide an alternative approach to finding effective therapeutic ruthenium-based agents with promising anticancer activity, and demonstrated that the BRCA1 RING domain protein was a promising therapeutic target for breast cancers.

Progress in research of the BRCA1 gene in gastric cancer

Chemotherapy occupies an important position in the treatment of gastric cancer. Platinum drugs are commonly chemotherapy drugs for gastric cancer; however, sensitivity to these drugs varies among different patients. The breast cancer susceptibility gene 1 (BRCA1) is a tumor suppressor gene that is associated with sensitivity to platinum drugs. At present, the research on the BRCA1 gene is mainly focused on breast cancer, and there have been fewer studies on gastric cancer. This paper will give an overview of the structure and function of the BRCA1 gene and the relationship between BRCA1 and gastric cancer.

The role of BRCA1 in DNA double-strand repair: past and present

The breast cancer type 1 susceptibility protein (BRCA1) is involved in several important cellular pathways, including DNA damage repair, chromatin remodeling and checkpoint activation. The BRCA1 tumor suppression function has been attributed to its role in homologous recombination damage repair. In this review, historical facts concerning BRCA1, together with recent research advances regarding our understanding of the BRCA1 interacting proteins that are involved in, homologous recombination (HR) double strand break (DBS) repair and how these interacting proteins maintain chromosomal integrity, are discussed. In addition, this review poses the questions as to what extent HR repair cannot be properly fulfilled when breast cancer related mutations in the BRCA1 gene occur and how the recent and excessive studied poly-ADP ribose polymerase (PARP) inhibiting therapy approach links with the proposed tumor suppression function of the different BRCA1 domains.

In Vitro Enhanced Sensitivity to Cisplatin in D67Y BRCA1 RING Domain Protein

BRCA1 is a tumor suppressor protein involved in maintaining genomic integrity through multiple functions in DNA damage repair, transcriptional regulation, cell cycle checkpoint, and protein ubiquitination. The BRCA1-BARD1 RING complex has an E3 ubiquitin ligase function that plays essential roles in response to DNA damage repair. BRCA1-associated cancers have been shown to confer a hypersensitivity to chemotherapeutic agents. Here, we have studied the functional consequence of the in vitro E3 ubiquitin ligase activity and cisplatin sensitivity of the missense mutation D67Y BRCA1 RING domain. The D67Y BRCA1 RING domain protein exhibited the reduced ubiquitination function, and was more susceptible to the drug than the D67E or wild-type BRCA1 RING domain protein. This evidence emphasized the potential of using the BRCA1 dysfunction as an important determinant of chemotherapy responses in breast cancer.