The role of extracellular matrix in tumour angiogenesis: the throne has NOx servants

Cytotoxic effect of crotoxin on cancer cells and its antitumoral effects correlated to tumor microenvironment: A review

Cancer is the second leading cause of death worldwide, and despite the effort of standard treatments, the search for new tools against this disease is necessary. Importantly, it is known that the tumor microenvironment plays a crucial role in tumor initiation, progression, and response to therapies. Therefore, studies of potential drugs that act on these components are as critical as studies regarding antiproliferative substances. Through the years, studies of several natural products, including animal toxins, have been conducted to guide the development of medical compounds. In this review, we present the remarkable antitumor activities of crotoxin, a toxin from the rattlesnake Crotalus durissus terrificus, highlighting its effects on cancer cells and in the modulation of relevant elements in the tumor microenvironment as well as the clinical trials conducted with this compound. In summary, crotoxin acts through several mechanisms of action, such as activation of apoptosis, induction of cell cycle arrest, inhibition of metastasis, and decrease of tumor growth, in different tumor types. Crotoxin also modulates tumor-associated fibroblasts, endothelial cells, and immune cells, which contribute to its antitumoral effects. In addition, preliminary clinical studies confirm the promising results of crotoxin and support its potential future use as an anticancer drug.

Targeted Therapy and Mechanisms of Drug Resistance in Breast Cancer

Breast cancer is the most common cause of cancer-related death in women worldwide. Multidrug resistance (MDR) has been a large hurdle in reducing BC death rates. The drug resistance mechanisms include increased drug efflux, enhanced DNA repair, senescence escape, epigenetic alterations, tumor heterogeneity, tumor microenvironment (TME), and the epithelial-to-mesenchymal transition (EMT), which make it challenging to overcome. This review aims to explain the mechanisms of resistance in BC further, identify viable drug targets, and elucidate how those targets relate to the progression of BC and drug resistance.

Interactions between Nitric Oxide and Hyaluronan Implicate the Migration of Breast Cancer Cells

Nitric oxide (^•NO) is one of the prominent free radicals, playing a pivotal role in breast cancer progression. Hyaluronic acid (HA) plays an essential role in neutralizing free radicals in tumor tissues. However, its interactions with nitric oxide have not been thoroughly investigated. Hence, this study attempts to understand the mechanism of these interactions and the different effects on the intracellular ^•NO levels and migration of breast cancer cells. The affinity of HA to scavenge ^•NO was investigated alongside the accompanying changes in specific physico-chemical properties and the further effects on the ^•NO-induced attachment and migration of the breast cancer cell lines, MDA-MB-231 and HCC1806. The reaction of the nitrogen dioxide radical, formed via ^•NO/O₂ interactions, with HA initiated a series of oxidative reactions, which, in the presence of ^•NO, induce the fragmentation of the polymeric chains. Furthermore, these interactions were found to hinder the NO-induced migration of cancer cells. However, the NO-induced HA modification/fragmentation was inhibited in the presence of hemin, a NO-scavenging compound. Collectively, these results help toward understanding the involvement of HA in the ^•NO-induced cell migration and suggest the possible modification of HA, used as one of the main materials in different biomedical applications.

Protein nitration induced by Hemin/NO: A complementary mechanism through the catalytic functions of hemin and NO-scavenging

Hemin and heme-peroxidases have been considered essential catalysts for the nitrite/hydrogen peroxide (H₂O₂)-mediated protein nitration in vitro, understood as one of the main pathways for protein modification in biological systems. However, the role of nitric oxide (^●NO) in the heme/hemin-induced protein nitration has not been studied in-depth. This is despite its reductive nitrosylating effects following binding to hemin and the possible involvement of the reactive nitrogen species in the nitration of various functional proteins. Here, the ^●NO-binding affinity of hemin has been studied along with the influence of ^●NO on the internalization of hemin into MDA-MB-231 cells and the accompanying changes in the profile of intracellular nitrated proteins. Moreover, to further understand the mechanism involved, bovine serum albumin (BSA) nitration was studied after treatment with hemin and ^●NO, with an investigation of the effects of pH of the reaction medium, generation of H₂O₂, and the oxidation of the tyrosine residues as the primary sites for the nitration. We demonstrated that hemin nitrosylation enhanced its cellular uptake and induced the one-electron oxidation and nitration of different intracellular proteins along with its ^●NO-scavenging efficiency. Moreover, the hemin/NO-mediated BSA nitration was proved to be dependent on the concentration of ^●NO and the pH of the reaction medium, with a vital role being played by the scavenging effects of protein for the free hemin molecules. Collectively, our results reaffirm the involvement of hemin and ^●NO in the nitration mechanism, where the nitrosylation products can induce protein nitration while promoting the effects of the components of the nitrite/H₂O₂-mediated pathway.

Differences of Angiogenesis Factors in Tumor and Diabetes Mellitus

Angiogenesis, as a process occurring under the regulation of a variety of factors, is one of the important ways of vascular development. It coexists in a variety of pathological and physiological processes. Now a large number of studies have proved that tumor growth, metastasis, and various vascular complications of diabetes are closely related to angiogenesis, and an increasing number of studies have shown that there are many common factors between the two. But angiogenesis is the opposite of the two: it is enhanced in tumors and suppressed in diabetes. Therefore, this review discusses the causes of the phenomenon from the expression of various factors affecting angiogenesis in these two diseases and their effects on angiogenesis in the relevant microenvironment, as well as the application status of these factors or cells as therapeutic targets in the treatment of these two diseases.