Comparison of mammosphere formation from stem-like cells of normal breast, malignant primary breast tumors, and MCF-7 cell line

BACKGROUND

Mammosphere formation assay has become a versatile tool to quantify the activity of putative breast cancer stem cells in non-adherent in vitro cultures. However, optimizing the suspension culture system is crucial to establish mammosphere cultures from primary breast tumors.

METHODS

This study aimed at determining the self-renewal and sphere-forming potential of breast cancer stem-like cells derived from human primary invasive ductal carcinoma and normal breast tissue samples, and MCF-7 breast cancer cell line using an optimal suspension culture system. Mammosphere-forming efficiency of the mammospheres generated from the tissue samples and cell line were compared. We evaluated the expression of CD44⁺/CD24^-/^low and CD49f⁺/EpCAM^-/^low phenotypes in the stem-like cells by flow cytometry. CK-18, CK-19, α-SMA, and EpCAM marker expression was assessed using immunohistochemical staining.

RESULTS

Breast epithelial cells isolated from the three samples formed two-dimensional spheroids in suspension cultures. Interestingly, mammospheres formed from patient-derived primary breast tumors were enriched in breast cancer stem-like cells with the phenotype CD44⁺/CD24^-/^low and exhibited a relatively more number of large spheres when compared to the normal breast stem cells. MCF-7-derived SCs were more aggressive and resulted in the formation of a significantly higher number of spheroids. The expression of CK-18/CK-19 and α-SMA/EpCAM proteins was confirmed in breast cancer tissues.

CONCLUSIONS

Thus, the use of primary tumor specimens and breast cancer cell lines as suitable models for elucidating the breast cancer stem cell activity was validated using mammosphere culture system.

Repurposing of potential antiviral drugs against RNA-dependent RNA polymerase of SARS-CoV-2 by computational approach

The high incidences of COVID-19 cases are believed to be associated with high transmissibility rates, which emphasizes the need for the discovery of evidence-based antiviral therapies for curing the disease. The rationale of repurposing existing classes of antiviral small molecule therapeutics against SARS-CoV-2 infection has been expected to accelerate the tedious and expensive drug development process. While Remdesivir has been recently approved to be the first treatment option for specific groups of COVID-19 patients, combinatory therapy with potential antiviral drugs may be necessary to enhance the efficacy in different populations. Hence, a comprehensive list of investigational antimicrobial drug compounds such as Favipiravir, Fidaxomicin, Galidesivir, GC376, Ribavirin, Rifabutin, and Umifenovir were computationally evaluated in this study. We performed in silico docking and molecular dynamics simulation on the selected small molecules against RNA-dependent RNA polymerase, which is one of the key target proteins of SARS-CoV-2, using AutoDock and GROMACS. Interestingly, our results revealed that the macrocyclic antibiotic, Fidaxomicin, possesses the highest binding affinity with the lowest energy value of -8.97 kcal/mol binding to the same active sites of RdRp. GC376, Rifabutin, Umifenovir and Remdesivir were identified as the next best compounds. Therefore, the above-mentioned compounds could be considered good leads for further preclinical and clinical experimentations as potentially efficient antiviral inhibitors for combination therapies against SARS-CoV-2.

Plant-Derived Antiviral Compounds as Potential Entry Inhibitors against Spike Protein of SARS-CoV-2 Wild-Type and Delta Variant: An Integrative in SilicoApproach

The wild-type SARS-CoV-2 has continuously evolved into several variants with increased transmissibility and virulence. The Delta variant which was initially identified in India created a devastating impact throughout the country during the second wave. While the efficacy of the existing vaccines against the latest SARS-CoV-2 variants remains unclear, extensive research is being carried out to develop potential antiviral drugs through approaches like in silico screening and drug-repurposing. This study aimed to conduct the docking-based virtual screening of 50 potential phytochemical compounds against a Spike glycoprotein of the wild-type and the Delta SARS-CoV-2 variant. Subsequently, molecular docking was performed for the five best compounds, such as Lupeol, Betulin, Hypericin, Corilagin, and Geraniin, along with synthetic controls. From the results obtained, it was evident that Lupeol exhibited a remarkable binding affinity towards the wild-type Spike protein (-8.54 kcal/mol), while Betulin showed significant binding interactions with the mutated Spike protein (-8.83 kcal/mol), respectively. The binding energy values of the selected plant compounds were slightly higher than that of the controls. Key hydrogen bonding and hydrophobic interactions of the resulting complexes were visualized, which explained their greater binding affinity against the target proteins-the Delta S protein of SARS-CoV-2, in particular. The lower RMSD, the RMSF values of the complexes and the ligands, Rg, H-bonds, and the binding free energies of the complexes together revealed the stability of the complexes and significant binding affinities of the ligands towards the target proteins. Our study suggests that Lupeol and Betulin could be considered as potential ligands for SARS-CoV-2 spike antagonists. Further experimental validations might provide new insights for the possible antiviral therapeutic interventions of the identified lead compounds and their analogs against COVID-19 infection.

Comparison of Immunological Profiles of SARS-CoV-2 Variants in the COVID-19 Pandemic Trends: An Immunoinformatics Approach

The current dynamics of the COVID-19 pandemic have become a serious concern with the emergence of a series of mutant variants of the SARS-CoV-2 virus. Unlike the previous strain, it is reported that the descendants are associated with increased risk of transmission yet causing less impact in terms of hospital admission, the severity of illness, or mortality. Moreover, the vaccine efficacy is also not believed to vary among the population depending on the variants of the virus and ethnicity. It has been determined that the mutations recorded in the spike gene and protein of the newly evolved viruses are specificallyresponsible for this transformation in the behavior of the virus and its disease condition. Hence, this study aimed to compare the immunogenic profiles of the spike protein from the latest variants of the SARS-CoV-2 virus concerning the probability of COVID-19 severity. Genome sequences of the latest SARS-CoV-2 variants were obtained from GISAID and NCBI repositories. The translated protein sequences were run against T-cell and B-cell epitope prediction tools. Subsequently, antigenicity, immunogenicity, allergenicity, toxicity, and conservancy of the identified epitopes were ascertained using various prediction servers. Only the non-allergic and non-toxic potential epitopes were matched for population relevance by using the Human Leucocyte Antigen population registry in IEDB. Finally, the selected epitopes were validated by docking and simulation studies. The evaluated immunological parameters would concurrently reveal the severity of COVID-19, determining the infection rate of the pathogen. Our immunoinformatics approach disclosed that spike protein of the five variants was capable of forming potential T and B-cell epitopes with varying immune responses. Although the Wuhan strain showed a high number of epitope/HLA combinations, relatively less antigenicity and higher immunogenicity results in poor neutralizing capacity, which could be associated with increased disease severity. Our data demonstrate that increased viral antigenicity with moderate to high immunogenicity, and several potential epitope/HLA combinations in England strain, the USA, India, and South Africa variants, could possess a high neutralizing ability. Therefore, our findings reinforce that the newly circulating variants of SARS-CoV-2 might be associated with more infectiousness and less severe disease condition despite their greater viremia, as reported in the recent COVID-19 cases, whichconsequently determine their increased epidemiological fitness.

Effects of the calcium antagonists perhexiline and cinnarizine on vascular and cardiac contractile protein function

The weakly basic, lipophilic Ca++ antagonists perhexiline and cinnarizine have been compared with the calmodulin inhibitor W-7 and the cardiotonics Vardax and APP-201-533 for the ability to modulate Ca++-dependent contractile protein interactions directly, as well as Ca++-calmodulin-mediated myosin light chain phosphorylation, in arterial actomyosin or cardiac myofibrils. Both perhexiline and cinnarizine inhibited arterial myosin P-light chain phosphorylation and superprecipitation of arterial actomyosin over the concentration range of 10 to 200 microM. Concomitant inhibition of arterial superprecipitation and phosphorylation by perhexiline (IC50 = 33 microM) and cinnarizine (IC50 = 60 microM) was similar to W-7 (IC50 = 35 microM), and was characterized by a rightward shift in the pCa superprecipitation and pCa-light chain phosphorylation relationships, depressed maximum activity and attenuation by 2 microM exogenous calmodulin. However, whereas inhibition of superprecipitation and P-light chain phosphorylation by W-7 was equal at different Mg++ concentrations, relatively greater inhibition with perhexiline and less inhibition with cinnarizine was apparent as the free Mg++ concentration was lowered. In cardiac myofibrils prepared from both bovine and canine ventricles, perhexiline stimulated Mg-adenosine triphosphatase (ATPase) activity and cinnarizine was without effect, whereas W-7 significantly depressed ATPase activity. Perhexiline was 10-fold more potent and 3-fold more efficacious than either Vardax or APP-201-533 in canine cardiac myofibrils. Whereas APP-201-533 increased Ca++ sensitivity and maximum ATPase activity (Vmax), perhexiline increased Ca++ sensitivity, but not Vmax, and W-7 depressed both parameters.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of felodipine, nitrendipine and W-7 on arterial myosin phosphorylation, actin-myosin interactions and contraction

The relative effects of felodipine, a dihydropyridine with purported calmodulin antagonistic properties, have been compared with the calmodulin inhibitor, W-7, for inhibition of Ca2+-dependent force development and direct inhibition of Ca2+-calmodulin mediated arterial myosin light chain phosphorylation and actin-myosin interactions. Felodipine (IC50 3 X 10(-9) M) was approximately 30 000 X more potent than W-7 (IC50 10(-4) M) and equipotent with another dihydropyridine, nitrendipine, in inhibiting isometric force development in K+-depolarized aortic smooth muscle strips. In contrast, W-7 (IC50 4 X 10(-5) M) was approximately 5 X more potent than felodipine (IC50 2 X 10(-4) M) in inhibiting Ca2+-dependent myosin light chain phosphorylation or superprecipitation of arterial actomyosin. Concentration-related inhibition of both parameters by W-7 was tightly coupled to concomitant inhibition of force development in intact smooth muscle. In contrast, inhibition of myosin light chain phosphorylation and superprecipitation by felodipine was only apparent at concentrations greater than or equal to 10(-5) M while maximal inhibition of force development occurred at a concentration as low as 10(-7) M. Inhibition of contractility by W-7 was minimal in paced rabbit atria, whereas inhibition by felodipine was similar to that seen with nitrendipine. These results suggest that the pharmacologically-relevant mechanism of Ca2+ antagonism in smooth muscle by felodipine is similar to nitrendipine (blockade of the Ca2+ entry channel) and does not involve direct inhibition of Ca2+-calmodulin stimulated myosin light chain phosphorylation and subsequent actin-myosin interactions.

Effects of calcium antagonists and vasodilators on arterial myosin phosphorylation and actin-myosin interactions

The mechanism of action of many direct-acting vascular smooth muscle relaxant agents is undefined. Moreover, an additional intracellular locus of action for some Ca++ entry blockers has been proposed. We have examined the potential for direct action by some of these agents at the level of smooth muscle contractile proteins by quantitating changes in Ca++-dependent superprecipitation of native arterial actomyosin. Moreover, inasmuch as previous research has linked phosphorylation of the 20,000 dalton myosin light chain to Ca++-dependent regulation of contraction, effects on myosin phosphorylation also were quantitated. Whereas the standard calmodulin antagonist W-7 inhibited both parameters by approximately 50% at 10(-4) M, diazoxide, hydralazine, 3-isobutyl-1-methylxanthine, papaverine, propranolol, nifedipine, nitrendipine, sodium nitroprusside and verapamil did not significantly inhibit either parameter at equimolar concentrations. Cyclandelate significantly delayed the onset of superprecipitation, but did not affect the extent of superprecipitation or myosin phosphorylation. The Ca++ antagonists felodipine and diltiazem inhibited superprecipitation by approximately 25%. However, unlike W-7, or felodipine, diltiazem did not concomitantly inhibit myosin phosphorylation. Inhibition of superprecipitation by diltiazem was apparent at a concentration of 10(-6) M, was manifest by a rightward shift in the pCa relationship and could be attenuated by exogenous calmodulin. These results show that most vasodilators do not have direct effects on smooth muscle contractile protein function. However, diltiazem may inhibit Ca++-dependent arterial actin-myosin interactions by a mechanism which is independent of regulation of myosin light chain phosphorylation.