ATR inhibition facilitates targeting of leukemia dependence on convergent nucleotide biosynthetic pathways.

Leukemia cells rely on two nucleotide biosynthetic pathways, de novo and salvage, to produce dNTPs for DNA replication. Here, using metabolomic, proteomic, and phosphoproteomic approaches, we show that inhibition of the replication stress sensing kinase ataxia telangiectasia and Rad3-related protein (ATR) reduces the output of both de novo and salvage pathways by regulating the activity of their respective rate-limiting enzymes, ribonucleotide reductase (RNR) and deoxycytidine kinase (dCK), via distinct molecular mechanisms. Quantification of nucleotide biosynthesis in ATR-inhibited acute lymphoblastic leukemia (ALL) cells reveals substantial remaining de novo and salvage activities, and could not eliminate the disease in vivo. However, targeting these remaining activities with RNR and dCK inhibitors triggers lethal replication stress in vitro and long-term disease-free survival in mice with B-ALL, without detectable toxicity. Thus the functional interplay between alternative nucleotide biosynthetic routes and ATR provides therapeutic opportunities in leukemia and potentially other cancers.Leukemic cells depend on the nucleotide synthesis pathway to proliferate. Here the authors use metabolomics and proteomics to show that inhibition of ATR reduced the activity of these pathways thus providing a valuable therapeutic target in leukemia

Identification of modulators of deoxyribonucleotide pools and replication stress in cancer

Regulation of intracellular deoxyribonucleotide triphosphate (dNTP) pools are critical for DNA replication and repair. DNA replication is a highly demanding process, which requires precise timing and supply of adequate unmodified dNTPs. Imbalanced dNTP pools can lead to genomic instability and result in cancer development. Several studies have reported cancer cells are more susceptible than normal cells to perturbations in the quantity, quality and balance of dNTP pools. Therefore, therapeutic agents targeting dNTP synthesis have been used for treatment of several types of cancer. Despite these studies, the molecular mechanisms that regulate quantity and quality of dNTP pools are not completely understood. Studying the crosstalk between metabolic and signaling mechanisms for regulation of dNTP pools are required to develop better pharmacological interventions against cancer.Dysregulation of dNTP pools can occur in different ways -Modulators of dNTP pools’ quantity: Similar to other major branches of cellularmetabolism, nucleotide biosynthesis consists of redundant and convergent biosynthetic pathways. dNTPs required for DNA replication and repair can be produced by the de novo pathway (DNP) or by the nucleoside salvage pathway (NSP). Therefore, both pathways are required to be targeted simultaneously to achieve therapeutic efficacy. !iiiModulators of dNTP pools’ quality: Reactive oxygen species (ROS), generated by bothendogenous and exogenous routes can pose a significant threat to cellular integrity by inducing oxidative damage. This results in DNA base modifications, formation of apurinic/apyrimidinic lesions, which can be mutagenic and lead to DNA damage. Hence, pharmacological intervention by redox modulators is being investigated as promising anti-cancer therapy.Regulation of dNTP pools by signaling pathways: Dysregulation of quantity or quality of dNTP pools lead to transient disruption of replication fork progression, termed as replication stress (RS), defined by accumulation of unprotected single-stranded DNA (ssDNA) at stalled replication forks. In order to protect genomic integrity, cells activate the replication stress response (RSR) pathway to limit the amount of ssDNA and subsequent DNA damage. However, the metabolic consequences of RSR on nucleotide metabolism are poorly understood.This thesis focuses on development of pharmacological modulators to regulate dNTP pools. Further it explores the interconnections between these dNTP pool modulators and replication stress to establish combination therapies against cancer.In Chapter 1, we identified metabolic alterations in response to ATR inhibition in acute lymphoblastic leukemia, and developed a combination therapy targeting the metabolic vulnerabilities.In Chapter 2, we developed a novel dCK (the rate-limiting enzyme of NSP) inhibitor, with improved metabolic stability and bioavailability. We studied preclinical pharmacokinetics and dose-response relationships of dCK inhibitor for translation to first in-human clinical trials.In Chapter 3, we evaluated a series of novel isoquinoline based thiosemicarbazone compounds to discover a highly potent copper ionophore which induces oxidative stress and DNA damage against aggressive solid tumor models.In Chapter 4, we designed and applied a metabolic modifier screen which identified multiple protein kinase inhibitors as having non-canonical targets within pyrimidine metabolism

Constraints on long range force from perihelion precession of planets in a gauged

The standard model leptons can be gauged in an anomaly free way by three possible gauge symmetries namely $${L_e-L_\mu }$$, $${L_e-L_\tau }$$, and $${L_\mu -L_\tau }$$. Of these, $${L_e-L_\mu }$$ and $${L_e-L_\tau }$$ forces can mediate between the Sun and the planets and change the perihelion precession of planetary orbits. It is well known that a deviation from the $$1/r^2$$ Newtonian force can give rise to a perihelion advancement in the planetary orbit, for instance, as in the well known case of Einstein’s gravity (GR) which was tested from the observation of the perihelion advancement of the Mercury. We consider the long range Yukawa potential which arises between the Sun and the planets if the mass of the gauge boson is $$M_{Z^{\prime }}\le \mathcal {O}(10^{-19})\mathrm {eV}$$. We derive the formula of perihelion advancement for Yukawa type fifth force due to the mediation of such $$U(1)_{L_e-L_{\mu ,\tau }}$$ gauge bosons. The perihelion advancement for Yukawa potential is proportional to the square of the semi major axis of the orbit for small $$M_{Z^{\prime }}$$, unlike GR where it is largest for the nearest planet. For higher values of $$M_{Z^{\prime }}$$, an exponential suppression of the perihelion advancement occurs. We take the observational limits for all planets for which the perihelion advancement is measured and we obtain the upper bound on the gauge boson coupling g for all the planets. The Mars gives the stronger bound on g for the mass range $$\le 10^{-19}\mathrm {eV}$$ and we obtain the exclusion plot. This mass range of gauge boson can be a possible candidate of fuzzy dark matter whose effect can therefore be observed in the precession measurement of the planetary orbits

Vector gauge boson radiation from compact binary systems in a gauged Lμ−Lτ scenario

The orbital period of a compact binary system decays mainly due to quadrupole gravitational radiation, which agrees with the observation to within one percent. Other types of radiation such as ultralight scalar or pseudoscalar radiation, massive vector boson radiation also contribute to the decay of orbital period as long as the mass of the emitted particle is less than the orbital frequency of the compact binary system. We obtain an expression of the energy loss due to the radiation of massive vector field from the neutron star-neutron star and neutron star-white dwarf binaries. Due to large chemical potential of the degenerate electrons, neutron stars have large muon charge. We derive the energy loss due to U(1)Lμ−Lτ gauge boson radiation from the binaries. For the radiation of vector boson, the mass is restricted by $M_{Z^