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Results for “Tumorigenesis”

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At least 19 recordsLinked to original sources

PubMed1977

Prolactin and murine mammary tumorigenesis: a review.

It is unequivocal that prolactin is an influential hormone in murine mammary tumorigenesis. The Berenblum hypothesis (7), a well-known theoretical model of tumorigenesis that depicts this oncogenic process as a two-step mechanism, i.e., initiation and promotion, is a conceptual scheme in which the action of prolactin in mammary tumorigenesis may be understood. According to this conceptual model, prolactin would participate in both the initiation and promotion steps of mammary tumorigenesis, In the initiation phase, variations in prolactin secretion appear to influence the metabolism of the mammary epithelium, so that the epithelium would be either more receptive to or refractory to an initiating agent (e.g., chemical carcinogen, physical carcinogens, oncogenic viruses, ets.) i.e., a permissive action. In the promotion phase, prolactin may act as either a promoter or an antipromoter of the "transformed" mammary epithelium. In promotion, the hormone may either directly or indirectly (via the ovary) stimulate mitotic activity of the "transformed" epithelium. In antipromotion the hormone, in the presence of requisite hormones (e.g., glucocorticoids), may synergistically induce differentiation (e.g., lactation) in the "transformed" epithelium. A tumor would result in the former (promotion) but not in the latter (antipromotion) case. Whether or not prolactin is significantly influential in human breast tumorigenesis remains to be determined. This is an extremely important area of research which is justifiably receiving increased attention. For if prolactin can be shown to influence human breast epithelium in a manner similar to its effect on rodent mammary tissue, then prophylactic and/of chemotherapeutic control of human breast tumorigenesis may be feasible by appropriate drug-mediated prolactin suppression.

Adrenal Glands↗

PubMed1979

Immunologic manipulation of DMBA tumorigenesis in hamster cheek pouch by DNCB contact hypersensitivity.

Hamster cheek pouches were sensitized with the potent allergen DNCB either before the initiation of DMBA tumorigenesis or by direct application to already developed tumors. Among animals treated prior to tumorigenesis induction there was an apparent delay in onset of tumors and decreased rate of tumor growth. Direct application of DNCB to already established tumors seemed to temporarily arrest tumor growth; later, however, tumor growth rate resumed to approximately that in untreated control animals. It is concluded that DNCB contact hypersensitivity may exert some influence on the DMBA tumorigenesis process as manifested by delay in tumor onset or by temporarily retarding growth of established tumors. It appears that DNCB sensitization prior to tumorigenesis is generally more effective than DNCB applied after tumor development.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1977

Oxygen-dependent chemical tumorigenesis in a Nicotiana hybrid: inhibition by ascorbic acid and dinitrophenol.

Aqueous solutions of molecular oxygen, per se, or in combination with either pyrogallol or 6-azauracil increased tumorigenesis in Nicotiana suaveolens X Nicotiana langsdorffii seedlings relative to control seedlings. The biological activities of the organic chemicals were O2-dependent, because the substitution of N2 or O2 or the degassing of 0.1-1 mM solutions of the compounds eliminated or greatly reduced their tumorigenic effects. Rates of tumorigenesis exceeded 95% for 0.5 mM solutions of either pyrogallol or 6-azauracil solutions in the presence of l mM O2. Although tumors developed in 20% of seedlings in the presence of 1 mM O2, alone, 4-5 times more tumors were induced by the organic chemical--O2-H2O systems. Dinitrophenol and ascorbic acid, compounds which affect cellular respiration or redox systems, strongly inhibited the chemically-mediated tumorigenesis. Dinitrophenol was equally effective at one-tenth of the molar concentrations of ascorbic acid that were required for the suppressions of oncogenesis. Dehydroascorbic acid was much less inhibitory than ascorbic acid.

Ascorbic Acid↗

PubMed2026

Targeting Both Oncogenic Signaling and Dependence Receptor Function is Required to Fully Suppress MET Exon 14 Skipping-Driven tumorigenesis.

Receptor tyrosine kinases (RTKs) classically function as oncogenic drivers that promote survival and proliferation upon ligand binding. A subset of RTKs can also function as dependence receptors, inducing apoptosis in the absence of their ligands. Genetic alterations that enhance RTK signaling are well characterized in cancer and can be targeted with kinase inhibitors, which show limited efficacy in some clinical settings. Elucidation of whether oncogenic mutations can promote tumorigenesis by directly abolishing the pro-apoptotic activity of dependence receptors could help improve strategies to target RTKs. Here, we identified MET exon 14 skipping (METex14Del) as a paradigmatic example of an oncogenic alteration that drives tumorigenesis through genetic inactivation of the dependence receptor function of an RTK. METex14Del removed both the caspase cleavage site and adjacent CBL-binding motif, preventing generation of the pro-apoptotic p40MET fragment while sustaining oncogenic MET signaling. Uncoupling regulatory functions of MET using genome editing showed that loss of apoptosis capacity is a critical determinant of METex14Del-driven tumorigenesis. Combined-but not individual-mutation of the caspase and CBL sites was sufficient to recapitulate resistance to apoptosis and tumor growth induced by METex14Del in HGF-humanized mouse models. Importantly, inducible re-expression of p40MET in METex14Del-expressing cells restored apoptotic sensitivity, decreased tumor formation in vivo, and resensitized tumors to capmatinib. Together, these findings redefine RTKs as receptors with dual oncogenic and tumor-suppressive functions and show that disruption of dependence receptor-mediated apoptosis is an oncogenic mechanism. These results provide a conceptual framework explaining why therapies targeting only RTK signaling may fail and support strategies restoring dependence receptor function to achieve durable tumor suppression.

Journal Article↗

PubMed1978

Suppression by Nocardia rubra cell wall skeleton mammary DNA synthesis, plasma prolactin level, and spontaneous mammary tumorigenesis in mice.

The effects of the cell wall skeleton of Nocardia rubra on mammary gland DNA synthesis, plasma prolactin levels, and spontaneous mammary tumorigenesis in mice were studied. Female SHN mice received s.c. injections of 100 microgram N. rubra cell wall every 7 days between 2 and 12 months of age. The treatment resulted in the marked inhibition of mammary tumorigenesis; incidence was significantly lower in the experimental mice than in the controls except at 9 and 12 months of age. The age of onset of mammary tumors was significantly higher in the former than in the latter. In association with these findings, the treatment also reduced normal mammary gland DNA synthesis and prolactin levels in the circulation, both of which are primary factors for mammary tumorigenesis.

Age Factors↗

PubMed1977

The role of the subependymal plate in glial tumorigenesis.

We have studied the sequential morphological events of glial tumorigenesis in neonatal dogs, using high titer subgroup C Bratislava-77 Avian Sarcoma Virus, given as 0.01 ml by intraventricular inoculation. The cells of the subependymal plate are those which seem to form the gliomas; cytoplasmic alterations are evident within 24 h after inoculation and microfoci of gliomas, contiguous with the subependymal plate of the lateral ventricles, are visible within 7 days. Independent tumors are present by the 10th post-inoculation day. These studies support the hypothesis of Globus and Kuhlenbeck, which implicates the cells of the subependymal palte in glial tumorigenesis.

Animals↗

PubMed2026

Dietary arginine drives codon-dependent MHC class I translation and improves immunity in colon tumorigenesis and respiratory viral infection.

Amino acid levels fluctuate across diverse pathological conditions. Whether such amino acid modulations directly shape pathophysiology by regulating host gene expression remains unknown. We found that extracellular arginine restriction, observed in cancer and infection, represses specific arginine tRNAs-directly suppressing translation of major histocompatibility complex I (MHC class I) and antigen presentation. Arginine regulation of MHC class I was codon-usage dependent, as synonymous codon mutations prevented MHC class I modulation. Dietary arginine restriction impaired anti-viral immunity against influenza and SARS-CoV-2 and increased colon tumorigenesis. Conversely, increasing arginine availability via dietary supplementation or myeloid-specific arginase 1 deletion enhanced MHC class I protein levels, suppressed colon tumorigenesis, and improved viral infection outcomes. These disease-modulating effects were abolished in β2-microglobulin (B2m)-deficient mice. Thus, dietary modulation of a single amino acid critically influences codon-biased translation and MHC class I-mediated immunity to respiratory viral infections and cancer, revealing an unexpected mechanism and disease hazard for arginine deficiency and highlighting potential for amino acid-based translation modulation therapy.

Animals↗

PubMed2022

Inhibition of RAS-driven signaling and tumorigenesis with a pan-RAS monobody targeting the Switch I/II pocket.

RAS mutants are major therapeutic targets in oncology with few efficacious direct inhibitors available. The identification of a shallow pocket near the Switch II region on RAS has led to the development of small-molecule drugs that target this site and inhibit KRAS(G12C) and KRAS(G12D). To discover other regions on RAS that may be targeted for inhibition, we have employed small synthetic binding proteins termed monobodies that have a strong propensity to bind to functional sites on a target protein. Here, we report a pan-RAS monobody, termed JAM20, that bound to all RAS isoforms with nanomolar affinity and demonstrated limited nucleotide-state specificity. Upon intracellular expression, JAM20 potently inhibited signaling mediated by all RAS isoforms and reduced oncogenic RAS-mediated tumorigenesis in vivo. NMR and mutation analysis determined that JAM20 bound to a pocket between Switch I and II, which is similarly targeted by low-affinity, small-molecule inhibitors, such as BI-2852, whose in vivo efficacy has not been demonstrated. Furthermore, JAM20 directly competed with both the RAF(RBD) and BI-2852. These results provide direct validation of targeting the Switch I/II pocket for inhibiting RAS-driven tumorigenesis. More generally, these results demonstrate the utility of tool biologics as probes for discovering and validating druggable sites on challenging targets.

Biological Products↗

PubMed1977

Enhancement of urethan tumorigenesis in mouse lung by butylated hydroxytoluene.

Intraperitoneal injection of the antioxidant butylated hydroxytoluene (BHT) produces cell proliferation in mouse lungs within 2-4 days. We examined whether the presence of an increased number of proliferating lung cells would influence urethan tumorigenesis. Male Swiss-Webster mice were treated with 1 mg urethan/g before, during, or after BHT-stimulated cell growth in the lung. The number of pulmonary tumors found 13-15 weeks later was not different in BHT-treated mice compared to that in controls. On the other hand, repeated stimulation of cell growth after urethan treatment enhanced tumorigenesis. Male Swiss-Webster and A/J mice were given a single dose of urethan (1 mg/g) and, beginning 7 days later, weekly injections of BHT or corn oil. Repeated injections of BHT significantly increased the yield of lung tumors in both strains. Weekly injections of BHT into mice pretreated with 0.9% NaCl reduced the number of spontaneous pulmonary adenomas.

Animals↗

PubMed1977

Delayed foreign-body tumorigenesis in mice infected with lactate dehydrogenase-elevating virus: Brief communication.

Female and male CBA/H mice were infected with lactate dehydrogenase virus (LDV). Two weeks later, these mice and noninfected controls received double sc implants of unplasticized vinyl chloride-vinyl acetate copolymer films (0.2 X 15 X 22 mm). Foreign-body (FB) tumorigenesis was delayed in LDV-infected females and males by 2 months. This result could not be explained by an effect of LDV on cellular immunity, inasmuch as cellular immunity does not influence the course of FB tumorigenesis.

Animals↗

PubMed2024

Hyd/UBR5 defines a tumor suppressor pathway that links Polycomb repressive complex to regulated protein degradation in tissue growth control and tumorigenesis.

Tumor suppressor genes play critical roles in normal tissue homeostasis, and their dysregulation underlies human diseases including cancer. Besides human genetics, model organisms such as Drosophila have been instrumental in discovering tumor suppressor pathways that were subsequently shown to be highly relevant in human cancer. Here we show that hyperplastic disc (Hyd), one of the first tumor suppressors isolated genetically in Drosophila and encoding an E3 ubiquitin ligase with hitherto unknown substrates, and Lines (Lin), best known for its role in embryonic segmentation, define an obligatory tumor suppressor protein complex (Hyd-Lin) that targets the zinc finger-containing oncoprotein Bowl for ubiquitin-mediated degradation, with Lin functioning as a substrate adaptor to recruit Bowl to Hyd for ubiquitination. Interestingly, the activity of the Hyd-Lin complex is directly inhibited by a micropeptide encoded by another zinc finger gene, drumstick (drm), which functions as a pseudosubstrate by displacing Bowl from the Hyd-Lin complex, thus stabilizing Bowl. We further identify the epigenetic regulator Polycomb repressive complex1 (PRC1) as a critical upstream regulator of the Hyd-Lin-Bowl pathway by directly repressing the transcription of the micropeptide drm Consistent with these molecular studies, we show that genetic inactivation of Hyd, Lin, or PRC1 resulted in Bowl-dependent hyperplastic tissue overgrowth in vivo. We also provide evidence that the mammalian homologs of Hyd (UBR5, known to be recurrently dysregulated in various human cancers), Lin (LINS1), and Bowl (OSR1/2) constitute an analogous protein degradation pathway in human cells, and that OSR2 promotes prostate cancer tumorigenesis. Altogether, these findings define a previously unrecognized tumor suppressor pathway that links epigenetic program to regulated protein degradation in tissue growth control and tumorigenesis.

Animals↗

PubMed2026

MYC-bound enhancer RNAs in cis regulate gene transcription and tumorigenesis.

Emerging evidence suggests that MYC binds RNAs, but its functional consequences remain unclear. Here, we integrate multiomics data and reveal that MYC broadly binds enhancer RNAs (eRNAs), which exhibit high cancer- and tissue-specific expression in cancer cell lines and patient tumors. Moreover, we developed a computational pipeline to identify potential cis-regulatory MYC-eRNA target genes, with most predicted eRNA-target pairs supported by RNA polymerase II-mediated chromatin interaction data. Among these, we functionally characterized MERG1 as an oncogenic eRNA that promotes breast cancer tumorigenesis. Mechanistically, MERG1 interacts with MYC to enhance its occupancy at the GREB1 promoter, driving chromatin remodeling and epigenetic activation. This process specifically amplifies GREB1 expression and promotes tumor progression. Last, nanoparticle-mediated delivery of antisense oligonucleotides targeting MERG1 suppresses MYC-mediated breast cancer growth. These results advance our understanding of the enhancer-driven regulation of gene expression and tumorigenesis and provide insights into the regulatory landscape of MYC in cancer.

Humans↗

PubMed1978

Histometric study of the pituitary in mice treated neonatally with steroids and the relationship between prolactin cells and mammary tumorigenesis.

Neonatal female mice of the BALB/cC3H/Crgl strain were given daily injections of 17 beta-estradiol, progesterone and prolactin, singly and in some combinations, for 5 days beginning within 36 hr after birth. Mice were killed at tumor age or by 12 months of age. Differential cell counts of the anterior pituitary showed that prolactin cells were more numerous in neomatally estrogen-treated mice and progesterone-treated intact mice than in control mice. Paired analysis of tumor-bearing and non-tumor-bearing mice of all groups revealed that the occurrence of prolactin cells was greater in the former than the latter. Counts of gonadotropes and thyrotropes did not show any significant correlation with mammary tumorigenesis. However, neonatal estrogen and/or progesterone treatment resulted in significantly decreased numbers of gonadotropes in intact mice. In ovariectomized mice, gonadotropes were significantly increased regardless of neonatal treatment. The present results support the suggestion that the stimulatory effects of neonatal steroid treatment of mammary tumorigenesis may be a consequence of increased prolactin secretion, resulting from sustained minimal estrogen secretion by the ovary.

Animals↗

PubMed1975

Changes in fine structure accompanying estrogen-induced tumorigenesis of Leydig cells in the mouse testis.

The development of estrogen-induced Leydig cell tumors in cryptorchid BALB/c mice was studied with the electron microscope. Changes in Leydig cell fine structure are apparent by 10 days after the s.c. implantation of a pellet of diethylstibestrol (DES). The smooth endoplasmic reticulum is diminished, and there is an increase in lipid droplets and free polysomes as compared with untreated cryptochid controls. These alterations persist as the Leydig cells proliferate to form focal areas of hyperplasia in the interstitial tissue. During this period of proliferation, activated macrophages containing large residual bodies appear among the Leydig cells. If DES treatment is continued for several months, malignant Leydig cell tumors, result. They are characterized by a nuclear and cytoplasmic pleomorphism of the Leydig cells and a decreased macrophage population. Virus-like particles are rarely seen within the cell during the period of tumorigenesis. Along with the reduction in smooth endoplasmic reticulum in the Leydig cells after DES treatment, evidence from the literature suggests that there is also a decrease in testosterone biosynthesis. However, it is not clear whether these two effect are correlated, since the level of the microsomal enzymes of steroid biosynthesis may vary independently of either the amount of smooth endoplasmic reticulum or the level of androgen secretion. The increase in lipid droplets seen in Leydig cells after DES treatment suggest the accumulation of precursors from the steroid biosynthetic pathway. The macrophages are though to represent scavenger cells, rather than a primary tumor cell population. The paucity of virus-like particles within altered Leydig cells implies that formed virus is not a prerequisite for tumorigenesis.

Animals↗

PubMed1976

Enhancement of pancreatic tumorigenesis of 4-hydroxyaminoquinoline 1-oxide by ethionine in rats.

The effect of ethionine on pancreatic tumorigenesis of 4-hydroxyaminoquinoline 1-oxide (4-HAQO) in rats was studied. The high incidence of hyperplastic nodules developed in the exocrine pancreas of animals receiving a single injection of 4-HAQO only or protein-deficient diet containing 0.5% ethionine for 4 days followed by 4-HAQO. The incidence of adenoma was higher than that of hyperplastic nodules and well-differentiated adenocarcinoma developed in 1 out of 12 animals receiving protein-deficient diet containing ethionine for 18 days followed by 4-HAQO. No tumor was found in the pancreas of animals that received 0.005N HCl without 4-HAQO. These results suggest that the pancreatic tumorigenesis of 4-HAQO is enhanced by ethionine.

4-Hydroxyaminoquinoline-1-oxide↗

PubMed2025

Unscheduled polyploidy synergizes with oncogenic mutations to enhance genome instability and tumorigenesis.

Polyploid Giant Cancer Cells (PGCCs) occur across multiple cancer types and are associated with therapy resistance, genome instability, disease progression, and metastasis. PGCCs can grow through endocycles, a variant cell cycle of alternating Growth (G) and DNA Synthesis (S) phases without cell division. Unlike programmed endocycles that occur during normal tissue development, PGCCs switch from mitotic cycles to unscheduled endocycles in response to stress. PGCCs can subsequently return to error-prone divisions which generate aneuploid daughter cells that contribute to disease progression. However, the regulation of PGCC cell cycles and contributions to cancer are still being defined. Filling this knowledge gap will lead to the development of improved cancer therapies. In this study, we used a molecular-genetic system in the model organism Drosophila melanogaster to examine how oncogenes interact with unscheduled endocycles in vivo. We found that several oncogenes promote bypass of an endocycle arrest, resulting in increased polyploid cell size and DNA content. The extent of this increased growth was dependent on the type of oncogenic mutation. When these polyploid cells returned to division, RasG12V promoted continued divisions of polyploid daughter cells with elevated genome instability. RasG12V expression during transient endocycles and subsequent divisions also induced expression of a matrix metalloprotease and a Wnt pathway ligand. Importantly, RasG12V with transient endocycles enhanced the growth of large, neoplastic tumors. These findings indicate that oncogenic mutations can synergize with transient, unscheduled endocycles to promote tumorigenesis with important broader implications for cancer prognosis and therapies.

Animals↗

PubMed1975

Cytopathological effects of estradiol on the arcuate nucleus of the female rat. A possible mechanism for pituitary tumorigenesis.

Large subcutaneous doses (2 mg/21 days) of estradiol valerate (EV) given over several months will induce a prolactin and growth hormone-secreting pituitary tumor in female rats. The medial basal hypothalami (MBHs) of such EV-treated animals were examined at different time intervals with light and electron microscopes to determine whether EV affects the MBH and to relate any observed effects to the process of tumorigenesis. The MBHs of extensively treated rats exhibited profound glial and neuronal changes. The filament content of astrocytes was greatly increased and large dense pleomorphic inclusions filled both astrocytic perikarya and processes. Degenerating neuronal elements have been observed in the neuropil of extensively treated animals. Dark cells identified as M cells were seen to engage in phagocytosis and were loaded with dense inclusions. Some neurons in MBH contained large quantities of lipofuscin that was different in appearance from that of normal females of the same age. The glial reaction developed gradually. At earlier stages of EV treatment there were fewer reactive glia and these contained fewer inclusions. Myelin figures often occurred in these early inclusions. Reactive glia in EV-treated rats did not appear in the preoptic area, dorsomedial nucleus or lateral hypothalamus but were found in ventromedial nucleus. Retired breeders and starvation-stressed rats resembled normal controls. These pathological changes in MBH may result from a direct effect of EV on the hypothalamus. It is possible that, in addition to its effects on the hypophysis, EV suppresses or injures hypophysiotropic cells in MBH, thus releasing pituitary chromophobes from inhibitory hypothalamic influences. This could result in hypersecretion and neoplasia.

Animals↗

PubMed2025

USP7 Inhibitors Destabilize EBNA1 and Suppress Epstein-Barr Virus Tumorigenesis.

Epstein-Barr virus (EBV) is a ubiquitous human ɣ-herpesvirus implicated in various malignancies, including Burkitt's lymphoma and gastric carcinomas. In most EBV-associated cancers, the viral genome is maintained as an extrachromosomal episome by the EBV nuclear antigen-1 (EBNA1). EBNA1 is considered to be a highly stable protein that interacts with the ubiquitin-specific protease 7 (USP7). Here, we show that pharmacological inhibitors and small interfering RNA (siRNA) targeting USP7 reduce EBNA1 protein levels in a proteosome-dependent manner. Proteomic analysis revealed that USP7 inhibitor GNE6776 altered the EBNA1 protein interactome, including disrupting USP7 association with EBNA1. GNE6776 also inhibited EBNA1 binding to EBV oriP DNA and reduced viral episome copy number. Transcriptomic studies revealed that USP7 inhibition affected chromosome segregation and mitotic cell division pathways in EBV+ cells. Finally, we show that GNE6776 selectively inhibited EBV+ gastric and lymphoid cell proliferation in cell culture and slowed EBV+ tumor growth in mouse xenograft models. These findings suggest that USP7 inhibitors perturb EBNA1 stability and function and may be exploited to treat EBV latent infection and tumorigenesis.

Ubiquitin-Specific Peptidase 7↗