Ratan Sadhukhan

Quercetin induces cytochrome‐c release and ROS accumulation to promote apoptosis and arrest the cell cycle in G2/M, in cervical carcinoma: signal cascade and drug‐DNA interaction

Small aromatic compounds like flavonoids can intercalate with DNA molecules bringing about conformational changes leading to reduced replication and transcription. Here, we have examined one dietary flavonoid, quercetin (found in many fruit and vegetables), for possible anti‐cancer effects, on HeLa cells originally derived from a case of human cervical cancer.

Interaction studies between biosynthesized silver nanoparticle with calf thymus DNA and cytotoxicity of silver nanoparticles.

The interaction of calf thymus DNA (CTDNA) with silver nanoparticles (SNP) has been investigated following spectroscopic studies, analysis of melting temperature (Tm) curves and hydrodynamic measurement. In spectrophotometric titration and thermal denaturation studies of CTDNA it was found that SNP can form a complex with double-helical DNA and the increasing value of Tm also supported the same. The association constant of SNP with DNA from UV-Vis study was found to be 4.1×10(3) L/mol. The fluorescence emission spectra of intercalated ethidium bromide (EB) with increasing concentration of SNP represented a significant reduction of EB intensity and quenching of EB fluorescence. The results of circular dichroism (CD) suggested that SNP can change the conformation of DNA. From spectroscopic, hydrodynamic, and DNA melting studies, SNP has been found to be a DNA groove binder possessing partial intercalating property. Cell cytotoxicity of SNP was compared with that of normal silver salt solution on HeLa cells. Our results show that SNP has less cytotoxicity compared to its normal salt solution and good cell staining property.

Diarylheptanoid–myricanone isolated from ethanolic extract of Myrica cerifera shows anticancer effects on HeLa and PC3 cell lines: signalling pathway and drug-DNA interaction

OBJECTIVE To test if myricanone (C21H24O5), a cyclic diarylheptanoid, has anticancer effects on two different cancer cell lines HeLa and PC3. The present study was conducted with a note on the drug-DNA interaction and apoptotic signalling pathway. METHODS Several studies like cytotoxicity, nuclear damage, annexin-V-fluorescein isothiocyanate (FITC)/propidium iodide (PI)-labelled apoptotic assay and cell cycle arrest, immunoblot and reverse transcriptase-polymerase chain reaction (RT-PCR) were used following standard protocols. Circular dichroism (CD) spectroscopy was also done to evaluate whether myricanone effectively interacted with DNA to bring about conformational changes that could strongly inhibit the cancer cell proliferation. RESULTS Myricanone showed a greater cytotoxic effect on PC3 cells than on HeLa cells. Myricanone promoted G0/G1 arrest in HeLa cells and S phase arrest in PC3 cells. Nuclear condensation and annexin V-FITC/PI studies revealed that myricanone promoted apoptotic cell death. CD spectroscopic data indicated that myricanone had an interaction with calf thymus DNA that changed DNA structural conformation. RT-PCR and immunoblot studies revealed that myricanone activated the apoptotic signalling cascades through down-regulation of transcription factors like nuclear factor-κB (NF-κB) (p65), and signal transducers and activators of transcription 3 (STAT3); cell cycle regulators like cyclin D1, and survivin and other signal proteins like Bcl-2 and up-regulation of Bax, caspase-9 and caspase-3. CONCLUSION Myricanone induced apoptosis in both types of cancer cells by triggering caspase activation, and suppression of cell proliferation by down-regulation of NF-κB and STAT3 signalling cascades, which makes it a suitable candidate for possible use in the formulation of therapeutic agent for combating cancer.

Synthesis and characterization of two Cu(II) complexes with a new pyrazole-based Schiff base ligand: crystallography, DNA interaction and antimicrobial activity of Ni(II) and Cu(II) complexes

Abstract Reaction of Cu(II) nitrate with a new pyrazole-based Schiff base ligand, 5-methyl-3-formylpyrazole-N-(2′-methylphenoxy)methyleneimine (MPzOA), afforded two types of Cu(II) complexes at different reaction temperatures, [Cu(MPzOA)(NO3)]2 (1) and [Cu(3,7,11,15-tetramethylporphyrin)(H2O)](NO3)2 (2), reported together with a Ni(II) complex, [Ni(MPzOA)2(H2O)2]Br2 (3). The compounds are characterized by single crystal X-ray structure analyses along with several physico-chemical and spectral parameters. Complex 1 is authenticated as a bis(μ-pyrazolato)dicopper(II), while 2 is a porphyrinogen and 3 is a distorted octahedral complex. Structural analyses of the complexes reveal that 1 crystallized in monoclinic P21/n space group while 2 and 3 crystallized in monoclinic C2/c space group. DNA-binding studies of the complexes have shown that the complexes interact with CT-DNA. DNA-cleavage studies with plasmid DNA have shown that 1 and 2 induce extensive DNA cleavage in the presence of H2O2 as an additive, whereas there is no change in degradation of super-coiled DNA by 3 in the presence of additive. The antimicrobial studies of the complexes against Escherichia coli DH5α bacteria strain indicated that all the complexes were capable of killing E. coli with different LD50 values.

Expression of Telomere-Associated Proteins is Interdependent to Stabilize Native Telomere Structure and Telomere Dysfunction by G-Quadruplex Ligand Causes TERRA Upregulation

Telomere DNA can form specialized nucleoprotein structure with telomere-associated proteins to hide free DNA ends or G-quadruplex structures under certain conditions especially in presence of G-quadruplex ligand. Telomere DNA is transcribed to form non-coding telomere repeat-containing RNA (TERRA) whose biogenesis and function is poorly understood. Our aim was to find the role of telomere-associated proteins and telomere structures in TERRA transcription. We silenced four [two shelterin (TRF1, TRF2) and two non-shelterin (PARP-1, SLX4)] telomere-associated genes using siRNA and verified depletion in protein level. Knocking down of one gene modulated expression of other telomere-associated genes and increased TERRA from 10q, 15q, XpYp and XqYq chromosomes in A549 cells. Telomere was destabilized or damaged by G-quadruplex ligand pyridostatin (PDS) and bleomycin. Telomere dysfunction-induced foci (TIFs) were observed for each case of depletion of proteins, treatment with PDS or bleomycin. TERRA level was elevated by PDS and bleomycin treatment alone or in combination with depletion of telomere-associated proteins.

Transcriptional up-regulation of TERT and TERC necessarily not mean higher telomerase activity: A report of telomerase inhibition with higher transcription of TERT, TERC and TERF2 in A549 cells treated with staurosporine.

Targeting telomerase is one of the approaches to kill cancer cells since almost 90% cancer are telomerase-positive. TERT and TERC are essential subunits of telomerase and a number of reports available regarding telomerase inhibitions due to inhibition of either of the essential subunits. Here, we present inhibition of telomerase activity with up-regulation of TERT and TERC in A549 cells treated with staurosporin, a potent protein kinase inhibitor. Staurosporin was known to inhibit telomerase and we also observed time-dependent telomerase inhibition by staurosporin. Notably, staurosporin up-regulates the transcription of TERT and TERC with time. This data implicates higher expression of TERT and TERC does not enhance telomerase activity always and there must be other post-transcriptional factors that regulate telomerase activity. Furthermore, staurosporine enhances TERF2 expression in a time-dependent manner implicating that it may alter native telomere structure. Staurosporine induced apoptosis is well-established fact. Here, we compared staurosporine induced telomerase inhibition and apoptosis induction in a time frame to elucidate whether these two events are independent or not in our case. We observed that significant apoptosis induction (12h) was earlier event than significant telomerase inhibition (24h) after staurosporine treatment. Our data suggests, staurosporine transcriptionally elevates TERT and TERC but reduces telomerase activity and may alter telomere native structure via up-regulation of TERF2. Higher transcription of essential subunits of telomerase does not assure higher telomerase activity. Since induction of apoptosis is earlier event than telomerase inhibition, staurosporine induces apoptosis independent of telomerase inhibition