Publications by authors named "Mohini Kamra"

15 Publications

  • Page 1 of 1

LIMK2-NKX3.1 Engagement Promotes Castration-Resistant Prostate Cancer.

Cancers (Basel) 2021 May 12;13(10). Epub 2021 May 12.

Department of Chemistry and Purdue University Center for Cancer Research, Purdue University, 560 Oval Drive, West Lafayette, IN 47907, USA.

NKX3.1's downregulation is strongly associated with prostate cancer (PCa) initiation, progression, and CRPC development. Nevertheless, a clear disagreement exists between NKX3.1 protein and mRNA levels in PCa tissues, indicating that its regulation at a post-translational level plays a vital role. This study identified a strong negative relationship between NKX3.1 and LIMK2, which is critical in CRPC pathogenesis. We identified that NKX3.1 degradation by direct phosphorylation by LIMK2 is crucial for promoting oncogenicity in CRPC cells and in vivo. LIMK2 also downregulates NKX3.1 mRNA levels. In return, NKX3.1 promotes LIMK2's ubiquitylation. Thus, the negative crosstalk between LIMK2-NKX3.1 regulates AR, ARv7, and AKT signaling, promoting aggressive phenotypes. We also provide a new link between NKX3.1 and PTEN, both of which are downregulated by LIMK2. PTEN loss is strongly linked with NKX3.1 downregulation. As NKX3.1 is a prostate-specific tumor suppressor, preserving its levels by LIMK2 inhibition provides a tremendous opportunity for developing targeted therapy in CRPC. Further, as NKX3.1 downregulates AR transcription and inhibits AKT signaling, restoring its levels by inhibiting LIMK2 is expected to be especially beneficial by co-targeting two driver pathways in tandem, a highly desirable requisite for developing effective PCa therapeutics.
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http://dx.doi.org/10.3390/cancers13102324DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8151535PMC
May 2021

Phosphorylation-dependent regulation of SPOP by LIMK2 promotes castration-resistant prostate cancer.

Br J Cancer 2021 Mar 14;124(5):995-1008. Epub 2020 Dec 14.

Department of Chemistry and Purdue University Center for Cancer Research, 560 Oval Drive, West Lafayette, IN, 47907, USA.

Background: SPOP, an E3 ubiquitin ligase adaptor, can act either as a tumour suppressor or a tumour promoter. In prostate cancer (PCa), it inhibits tumorigenesis by degrading several oncogenic substrates. SPOP is the most altered gene in PCa (~15%), which renders it ineffective, promoting cancer. The remaining PCa tumours, which retain WT-SPOP, still progress to castration-resistant (CRPC) stage, indicating that other critical mechanisms exist for downregulating SPOP. SPOP is reduced in ~94% of WT-SPOP-bearing prostate tumours; however, no molecular mechanism is known for its downregulation.

Methods: SPOP was identified as a direct target of LIMK2 using an innovative technique. The reciprocal relationship between SPOP and LIMK2 and its consequences on oncogenicity were analysed using a variety of biochemical assays. To probe this relationship in vivo, xenograft studies were conducted.

Results: LIMK2 degrades SPOP by direct phosphorylation at three sites. SPOP promotes LIMK2's ubiquitylation, creating a feedback loop. SPOP's degradation stabilises AR, ARv7 and c-Myc promoting oncogenicity. Phospho-resistant SPOP completely suppresses tumorigenesis in vivo, indicating that LIMK2-mediated SPOP degradation is a key event in PCa progression.

Conclusions: While genomically altered SPOP-bearing tumours require gene therapy, uncovering LIMK2-SPOP relationship provides a powerful opportunity to retain WT-SPOP by inhibiting LIMK2, thereby halting disease progression.
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http://dx.doi.org/10.1038/s41416-020-01197-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7921662PMC
March 2021

Molecular Interplay between AURKA and SPOP Dictates CRPC Pathogenesis via Androgen Receptor.

Cancers (Basel) 2020 Nov 4;12(11). Epub 2020 Nov 4.

Department of Chemistry and Purdue University Center for Cancer Research, Purdue University, 560 Oval Drive, West Lafayette, IN 47907, USA.

SPOP, an adaptor protein for E3 ubiquitin ligase can function as a tumor-suppressor or a tumor-enhancer. In castration-resistant prostate cancer (CRPC), it inhibits tumorigenesis by degrading many oncogenic targets, including androgen receptor (AR). Expectedly, SPOP is the most commonly mutated gene in CRPC (15%), which closely correlates with poor prognosis. Importantly, 85% of tumors that retain wild-type SPOP show reduced protein levels, indicating that SPOP downregulation is an essential step in CRPC progression. However, the underlying molecular mechanism remains unknown. This study uncovered the first mechanism of SPOP regulation in any type of cancer. We identified SPOP as a direct substrate of Aurora A (AURKA) using an innovative technique. AURKA directly phosphorylates SPOP at three sites, causing its ubiquitylation. SPOP degradation drives highly aggressive oncogenic phenotypes in cells and in vivo including stabilizing AR, ARv7 and c-Myc. Further, SPOP degrades AURKA via a feedback loop. SPOP upregulation is one of the mechanisms by which enzalutamide exerts its efficacy. Consequently, phospho-resistant SPOP fully abrogates tumorigenesis and EMT in vivo, and renders CRPC cells sensitive to enzalutamide. While genomic mutations of SPOP can be treated with gene therapy, identification of AURKA as an upstream regulator of SPOP provides a powerful opportunity for retaining WT-SPOP in a vast majority of CRPC patients using AURKA inhibitors ± enzalutamide, thereby treating the disease and inhibiting its progression.
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http://dx.doi.org/10.3390/cancers12113247DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7693105PMC
November 2020

Negative cross talk between LIMK2 and PTEN promotes castration resistant prostate cancer pathogenesis in cells and in vivo.

Cancer Lett 2021 02 12;498:1-18. Epub 2020 Sep 12.

Department of Chemistry and Purdue University Center for Cancer Research 560 Oval Drive, West Lafayette, IN, 47907, USA. Electronic address:

Androgen deprivation therapy (ADT) and androgen receptor (AR) signaling inhibitors are front-line treatments for highly aggressive prostate cancer. However, prolonged inhibition of AR triggers a compensatory activation of PI3K pathway, most often due to the genomic loss of tumor suppressor PTEN, driving progression to the castration-resistant prostate cancer (CRPC) stage, which has very poor prognosis. We uncovered a novel mechanism of PTEN downregulation triggered by LIMK2, which contributes significantly to CRPC pathogenesis. LIMK2 is a CRPC-specific target. Its depletion fully reverses tumorigenesis in vivo. LIMK2 phosphorylates PTEN at five sites, degrading and inhibiting its activity, thereby driving highly aggressive oncogenic phenotypes in cells and in vivo. PTEN also degrades LIMK2 in a feedback loop, which was confirmed in prostates from PTEN and PTEN mice. LIMK2 is also the missing link between hypoxia and PTEN degradation in CRPC. This is the first study to show a feedback loop between PTEN and its regulator. Uncovering the LIMK2-PTEN loop provides a powerful therapeutic opportunity to retain the activity and stability of PTEN protein by inhibiting LIMK2, thereby halting the progression to CRPC, ADT-resistance and drug-resistance.
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http://dx.doi.org/10.1016/j.canlet.2020.09.010DOI Listing
February 2021

Specific stabilization of promoter G-Quadruplex DNA by 2,6-disubstituted amidoanthracene-9,10-dione based dimeric distamycin analogues and their selective cancer cell cytotoxicity.

Eur J Med Chem 2020 Jun 16;195:112202. Epub 2020 Mar 16.

Department of Organic Chemistry, Indian Institute of Science, Bangalore, 560012, India; School of Applied & Interdisciplinary Sciences, Indian Association for the Cultivation of Science, Kolkata, 700032, India. Electronic address:

We have designed and synthesized anthraquinone containing compounds which have oligopyrrole side chains of varying lengths. These compounds stabilized the G-quadruplex DNA formed in the promoter regions of c-MYC oncogenes selectively over the duplex DNA. These observations were recorded using UV-vis spectroscopic titrations, fluorescence measurements and circular dichroism (CD) spectral titrations. The potency of the compounds to stabilize the G4 DNA has been shown from the thermal denaturation experiments. The compound interacts with c-MYC G-quadruplex DNA through stacking mode as obtained from ethidium bromide displacement assay, cyclic voltammetric titration, and docking experiments. Molecular modeling studies suggested that the stacking of the anthraquinone moiety over the G-tetrad of the G4 structures are responsible for the stability of such quadruplex secondary structure. Furthermore, polymerase stop assay also supported the formation of stable G4 structures in the presence of the above-mentioned compounds. The compounds have shown selective cancer cell (HeLa and HEK293T) cytotoxicity over normal cells (NIH3T3 and HDFa) under in vitro conditions as determined from MTT based cell viability assay. Apoptosis was found to be the mechanistic pathway underlying the cancer cell cytotoxicity as obtained from Annexin V-FITC and PI dual staining assay which was further substantiated by nuclear morphological changes as observed by AO/EB dual staining assay. Cellular morphological changes, as well as nuclear condensation and fragmentation upon treatment with these compounds, were observed under bright field and confocal microscopy.
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http://dx.doi.org/10.1016/j.ejmech.2020.112202DOI Listing
June 2020

New Water-Soluble Oxyamino Chitosans as Biocompatible Vectors for Efficacious Anticancer Therapy via Co-Delivery of Gene and Drug.

ACS Appl Mater Interfaces 2019 Oct 7;11(41):37442-37460. Epub 2019 Oct 7.

Among the many nonviral gene delivery vectors, chitosan, being a polysaccharide of natural origin, has gained special importance. In this report, chitosan (CS) has been solubilized in water by preparing its carboxymethyl derivative, CS(CHCOOH), with an optimum degree of carboxymethylation. This has been further derivatized to get the pyridine-substituted product (py)CS(CHCOOH), where the degree of pyridine substitution (47%) was optimized based on zeta potential measurements. The optimized formulation showed a high gene binding ability, forming nanosized positively charged polyelectrolyte complexes with DNA. These polyplexes were stable to DNase and physiological polyanions such as heparin. They also exhibited minimal toxicity in vitro and showed transfection levels comparable to the commercial standard Lipofectamine 2000 and much higher than polyethylenimine (MW, 25 kDa). Additionally, in this study, a hitherto unknown oxyamine derivative of chitosan has been prepared by phthaloyl protection, tosylation, and Gabriel's phthalimide synthesis. Nearly 40% of the primary alcohols were successfully converted to oxyamino functionality, which was used for forming oxime with the anticancer drug doxorubicin. The pH sensitivity of the oxime ether linkage and stability under biologically relevant conditions were then used to establish the compound as a versatile drug delivery vector. Co-delivery of functional gene (p53) and drug (doxorubicin) was accomplished in vitro and in vivo with the chitosan-pyridine imine vector (py)CS(CHCOOH) and the newly synthesized doxorubicin oxime ether CS(Dox). Complete tumor regression with no tumor recurrence and appreciable survivability point to the in vivo effectiveness and biocompatibility of the designed composite formulation. Overall, the pH sensitivity of the oxime linkage aiding slow and steady drug release, together with the sustained gene expression by pyridine-tethered carboxymethyl chitosan, allows us to generate a nanobiocomposite with significantly high anticancer therapeutic potential.
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http://dx.doi.org/10.1021/acsami.9b09485DOI Listing
October 2019

Tumor Chemosensitization through Oncogene Knockdown Mediated by Unique α-Tocopherylated Cationic Geminis.

Biomacromolecules 2019 04 25;20(4):1555-1566. Epub 2019 Mar 25.

Department of Organic Chemistry , Indian Institute of Science , Bangalore 560012 , India.

Herein, siRNA transfection efficiency of a unique set of α-tocopherylated gemini lipids has been established in vitro and in vivo. High efficacy of oncogene silencing achieved using the biomacromolecular assembly, formed from siRNA complexes of co-liposomes containing an α-tocopherylated gemini lipid, has been utilized for tumor regression via chemosensitization. Delivery studies with the gemini bearing hydroxyethyl headgroup with octamethylene spacer (TH8S) pointed to a higher siRNA transfection efficacy than its analog without hydroxyethyl group (T8S). Owing to p53 upregulation, transfected cells showed enhanced sensitivity to the chemotherapeutic agent, doxorubicin. Studies in murine model revealed significantly low levels of survivin mRNA in xenograft tumors injected with siRNA lipoplexes, leading to effective inhibition of tumor growth and an increase in sensitivity of the tumors toward doxorubicin. These findings enable us to propose the anti-survivin siRNA carrying TH8S co-liposomes as a potent member of cancer management strategies using suicide gene therapy.
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http://dx.doi.org/10.1021/acs.biomac.8b01751DOI Listing
April 2019

Simultaneous sensing of ferritin and apoferritin proteins using an iron-responsive dye and evaluation of physiological parameters associated with serum iron estimation.

J Mater Chem B 2019 02 23;7(6):986-993. Epub 2019 Jan 23.

Department of Organic Chemistry, Indian Institute of Science, Bangalore 560012, India.

An iron-responsive optical probe has been developed for simultaneous sensing of both ferritin and apoferritin proteins at pH 7.4 in water. The compound showed an exclusive response (turn-off signal) towards ferritin among a wide range of proteins even at nanomolar concentration. In contrast, apoferritin dissociates the preformed iron complex and revives the green colored fluorescence of the native probe (turn-on signal). Subsequently, various parameters associated with the serum iron level are evaluated, which are beneficial for clinical diagnosis of many iron-related diseases, including anemia. Estimation of iron was achieved in a wide range of edible plant materials as well as pharmaceutical formulations. Subsequently, different kinds of natural water samples were screened for quantification of soluble iron contents. In addition to traditional spectroscopic tools, dye-coated paper strips were developed as an alternative strategy for onsite 'instrument-free' detection of iron. Highly specific bioimaging of Fe was achieved in cervical cancer cells (HeLa).
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http://dx.doi.org/10.1039/c8tb01523fDOI Listing
February 2019

Correction: Transfection efficiencies of α-tocopherylated cationic gemini lipids with hydroxyethyl bearing headgroups under high serum conditions.

Org Biomol Chem 2019 02;17(8):2288

Department of Organic Chemistry, Indian Institute of Science, Bangalore 560012, India.

Correction for 'Transfection efficiencies of α-tocopherylated cationic gemini lipids with hydroxyethyl bearing headgroups under high serum conditions' by Bappa Maiti et al., Org. Biomol. Chem., 2018, 16, 1983-1993.
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http://dx.doi.org/10.1039/c9ob90009hDOI Listing
February 2019

Transfection efficiencies of α-tocopherylated cationic gemini lipids with hydroxyethyl bearing headgroups under high serum conditions.

Org Biomol Chem 2018 03;16(11):1983-1993

Department of Organic Chemistry, Indian Institute of Science, Bangalore 560012, India.

Herein, five new α-tocopheryl cationic gemini lipids with hydroxyethyl bearing headgroups (THnS, n = 4, 5, 6, 8, 12) have been synthesized for efficient plasmid DNA (pDNA) delivery into cancer cells. Among these gemini lipid formulations, the lipid with an octamethylene [-(CH)] spacer (TH8S) showed the highest transfection efficiency (TE) that was comparable to that of the commercial standard lipofectamine 2000 (L2K) in terms of luciferase expression in HepG2 (liver hepatocellular carcinoma) cells. The addition of the helper lipid DOPE (1,2-dioleoyl phosphatidyl ethanolamine) with cationic lipids in mixed liposomes further enhanced the TE and the optimized molar ratio was 2 : 1 (DOPE : cationic lipid). The optimized co-liposomal formulation of TH8S (DOPE : TH8S = 2 : 1) showed a higher TE in HepG2, A549 (human lung carcinoma) and MCF7 (human breast adenocarcinoma) cells than other optimized co-liposomal formulations and was also significantly more potent than L2K. The comparison of the TE of DOPE-TH8S (2 : 1) with the gemini lipid T8T (the headgroup devoid of the hydroxyl group) further demonstrated the importance of the hydroxyethyl functionality at the level of the headgroup. Relatively good binding efficiency and easy release of pDNA (pGL3) were also observed with DOPE-TH8S (2 : 1) in the ethidium bromide (EB)-exclusion and re-intercalation assay, which may be the plausible reason for high TE. The lipoplexes were also characterized by atomic force microscopy (AFM), dynamic light scattering (DLS), zeta potential and small angle X-ray diffraction experiments. Greater cellular internalization of fluorescein tagged pDNA was also observed with DOPE-TH8S (2 : 1) lipoplexes compared to that with L2K. Retention of the TE of DOPE-TH8S (2 : 1) lipoplexes under high serum conditions was conferred by the presence of the tocopherol backbone and also the hydroxyethyl functionalities. The cellular internalization pathway of the lipoplexes was characterized by performing transfection experiment in the presence of inhibitors of different endocytic pathways and it was found to be caveolae mediated. An MTT based cell viability assay indicated that the lipoplex mediated gene delivery vectors exhibited low toxicity in all the three cancer cell lines studied.
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http://dx.doi.org/10.1039/c7ob02835kDOI Listing
March 2018

Identification of a flavonoid isolated from plum (Prunus domestica) as a potent inhibitor of Hepatitis C virus entry.

Sci Rep 2017 06 21;7(1):3965. Epub 2017 Jun 21.

Department of Biochemistry, Indian Institute of Science, Bangalore, 560012, India.

Hepatitis C virus (HCV) infection is a major cause of chronic liver diseases that often requires liver transplantation. The standard therapies are limited by severe side effects, resistance development, high expense and in a substantial proportion of cases, fail to clear the infection which bespeak the need for development of well-tolerated antivirals. Since most of the drug development strategies target the replication stage of viral lifecycle, the identification of entry inhibitors might be crucial especially in case of liver-transplant recipients. In the present study we have evaluated fruits which are known for their hepatoprotective effects in order to screen for entry inhibitors. We report the identification of a flavonoid, rutin, isolated from Prunus domestica as a new HCV entry inhibitor. Characterization and confirmation of the chemical structure was done by LC-ESI-MS, NMR and IR spectral analyses. Rutin significantly inhibited HCV-LP binding to hepatoma cells and inhibited cell-culture derived HCV (HCVcc) entry into hepatoma cells. Importantly, rutin was found to be non-toxic to hepatoma cells. Furthermore, rutin inhibits the early entry stage of HCV lifecycle possibly by directly acting on the viral particle. In conclusion, rutin is a promising candidate for development of anti-HCV therapeutics in the management of HCV infection.
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http://dx.doi.org/10.1038/s41598-017-04358-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5479801PMC
June 2017

A plant-derived dehydrorotenoid: a new inhibitor of hepatitis C virus entry.

FEBS Lett 2017 05 13;591(9):1305-1317. Epub 2017 Apr 13.

Department of Biochemistry, Indian Institute of Science, Bangalore, India.

Emergence of drug-resistant viruses, high cost and adverse side-effects associated with the standard therapy against hepatitis C virus (HCV) infection demonstrate the need for development of well tolerated and effective antivirals. We identified and chemically characterised the dehydrorotenoid boeravinone H, isolated from the herb Boerhavia diffusa, as a new inhibitor of HCV entry. The compound significantly inhibits the binding and entry of hepatitis C-like particles (HCV-LPs) in hepatoma cells in vitro with no apparent cytotoxicity. Boeravinone H inhibits the initial phase of HCV entry probably by acting directly on the viral particle. Importantly, the compound prevents HCV entry and infection in cell culture (ex vivo). Thus, boeravinone H is a potential antiviral agent for the prevention and control of HCV infection.
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http://dx.doi.org/10.1002/1873-3468.12629DOI Listing
May 2017

Enhanced G-Quadruplex DNA Stabilization and Telomerase Inhibition by Novel Fluorescein Derived Salen and Salphen Based Ni(II) and Pd(II) Complexes.

Bioconjug Chem 2017 02 6;28(2):341-352. Epub 2017 Feb 6.

Director's Research Unit, Indian Association for the Cultivation of Science , Kolkata 700 032, India.

Metal based salen complexes have been considered as an important scaffold toward targeting of DNA structures. In the present work, we have synthesized nickel(II) and palladium(II) salen and salphen complexes by using readily available fluorescein as the backbone to provide an extended aromatic surface. The metal complexes exhibit affinity toward the human telomeric G-quadruplex DNA with promising inhibition of telomerase activity. This has been ascertained by their efficiency in the long term cell proliferation assay which showed significant cancer cell toxicity in the presence of the metal complexes. Confocal microscopy showed cellular internalization followed by localization in the nucleus and mitochondria. Considerable population at the sub-G1 phase of the cell cycle showed cell death via apoptotic pathway.
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http://dx.doi.org/10.1021/acs.bioconjchem.6b00433DOI Listing
February 2017

Novel Oligopyrrole Carboxamide based Nickel(II) and Palladium(II) Salens, Their Targeting of Human G-Quadruplex DNA, and Selective Cancer Cell Toxicity.

Chem Asian J 2016 Sep 8;11(18):2542-54. Epub 2016 Sep 8.

Department of Organic Chemistry, Indian Institute of Science, Bangalore, 560 012, India.

DNA targeting by various metal complexes is a key strategy toward the restriction of cancer cell proliferation. Toward this end, we designed and synthesized novel salen-based Ni(II) and Pd(II) metal complexes with positively charged flanking side chains comprising N-methylpyrrole carboxamides of varying lengths. The compounds showed high specificity toward G-quadruplex DNA over duplex DNA. Sufficient inhibition of the telomerase activity was observed, which was ascertained by the prominent restriction of cancer cell proliferation in the long-term cell viability and telomerase inhibition assays. The compounds exhibited selective cancer cell death following an apoptotic pathway. Analysis of the binding mode showed partial stacking of the salen moiety over the G-tetrads and association of the pendant oligopyrrole carboxamide units with the grooves. The conjugation of the tetrad-binding metal salen core with groove-oriented flexible oligopyrrole moieties resulted in the high selectivity and stabilization of the human G-quadruplex DNA structures.
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http://dx.doi.org/10.1002/asia.201600655DOI Listing
September 2016

New Fe(iii) and Co(ii) salen complexes with pendant distamycins: selective targeting of cancer cells by DNA damage and mitochondrial pathways.

Dalton Trans 2016 May;45(22):9345-53

Department of Organic Chemistry, Indian Institute of Science, Bangalore 560 012, India and Indian Association for the Cultivation of Science, Kolkata, West Bengal 700 032, India.

Minor groove binding distamycin like moieties were conjugated with core salens and the corresponding Fe(iii) and Co(ii) complexes were synthesized. Herein, we have shown efficient DNA minor groove binding specificities along with excellent DNA cleavage capacities with metallosalen conjugates. The metal complexes showed toxicity toward various cancer cells over normal cells with high specificity. Interestingly, the Co(ii) complexes exhibited greater activity than the Fe(iii) complexes in accordance with the stronger affinity of the former in the biophysical studies. Active DNA damage, and prominent nuclear condensation along with the release of cytochrome-c from the mitochondria unanimously showed that the metal complexes followed apoptotic pathways to induce cell death.
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http://dx.doi.org/10.1039/c5dt04374cDOI Listing
May 2016