sirolimus and Precancerous-Conditions

PTEN is one of the most frequently mutated tumor suppressor genes in human cancers. The role of PTEN in carcinogenesis has been validated by knockout mouse models. PTEN heterozygous mice develop neoplasms in multiple organs. Unfortunately, the embryonic lethality of biallelic excision of PTEN has inhibited the study of complete PTEN deletion in the development and progression of cancer. By crossing PTEN conditional knockout mice with transgenic mice expressing a tamoxifen-inducible Cre-ER(T) under the control of a chicken actin promoter, we have generated a tamoxifen-inducible mouse model that allows temporal control of PTEN deletion. Interestingly, administration of a single dose of tamoxifen resulted in PTEN deletion mainly in epithelial cells, but not in stromal, mesenchymal or hematopoietic cells. Using the mT/mG double-fluorescent Cre reporter mice, we demonstrate that epithelial-specific PTEN excision was caused by differential Cre activity among tissues and cells types. Tamoxifen-induced deletion of PTEN resulted in extremely rapid and consistent formation of endometrial in situ adenocarcinoma, prostate intraepithelial neoplasia and thyroid hyperplasia. We also analyzed the role of PTEN ablation in other epithelial cells, such as the tubular cells of the kidney, hepatocytes, colonic epithelial cells or bronchiolar epithelium, but those tissues did not exhibit neoplastic growth. Finally, to validate this model as a tool to assay the efficacy of anti-tumor drugs in PTEN deficiency, we administered the mTOR inhibitor everolimus to mice with induced PTEN deletion. Everolimus dramatically reduced the progression of endometrial proliferations and significantly reduced thyroid hyperplasia. This model could be a valuable tool to study the cell-autonomous mechanisms involved in PTEN-loss-induced carcinogenesis and provides a good platform to study the effect of anti-neoplastic drugs on PTEN-negative tumors.

Topics: Adenocarcinoma; Alleles; Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Endometrial Neoplasms; Endometrium; Epithelial Cells; Everolimus; Female; Gene Deletion; Humans; Hyperplasia; Integrases; Male; Mice; Mice, Knockout; Precancerous Conditions; Prostatic Intraepithelial Neoplasia; Prostatic Neoplasms; PTEN Phosphohydrolase; Recombination, Genetic; Sirolimus; Stromal Cells; Tamoxifen; Thyroid Gland; Thyroid Neoplasms

Protein malnutrition occurs when there is insufficient protein to meet metabolic demands. Previous works have indicated that cycles of protein fasting/refeeding enhance the incidence of early lesions during chemical carcinogenesis in rat liver. The general objective of this work was to study the effect of aminoacids (Aa) deprivation on the proliferation and survival of hepatocytes, to understand its possible involvement in the generation of pre-neoplastic stages in the liver. Lack of Aa in the culture medium of an immortalized mice hepatocyte cell line induced loss in cell viability, correlating with apoptosis. However, a subpopulation of cells was able to survive, which showed a more proliferative phenotype and resistance to apoptotic stimuli. Escaping to Aa deprivation-induced death is coincident with an activated mTOR signaling and higher levels of phospho-AKT and phospho-ERKs, which correlated with increased activation of EGFR/SRC pathway and overexpression of EGFR ligands, such as TGF-α and HB-EGF. Lack of Aa induced a rapid increase in reactive oxygen species (ROS) production. However, cells that survived showed an enhancement in the levels of reduced glutathione and a higher expression of γ-GCS, the regulatory enzyme of glutathione synthesis, which can be interpreted as an adaptation of the cells to counteract the oxidative stress. In conclusion, results presented in this paper indicate that it is possible to isolate a subpopulation of hepatocytes that are able to grow in the absence of Aa, showing higher capacity to proliferate and survive, reminiscent of a preneoplastic phenotype.

Topics: Amino Acids; Animals; Caspase 3; Cell Line, Transformed; Cell Proliferation; Cell Survival; Cell Transformation, Neoplastic; Culture Media; Enzyme Activation; Enzyme Assays; Hepatocytes; Liver; Mice; Oxidation-Reduction; Oxidative Stress; Phosphoproteins; Phosphorylation; Precancerous Conditions; Protein-Energy Malnutrition; Signal Transduction; Sirolimus

Oval cell activation occurs under conditions of severe liver injury when normal hepatocyte proliferation is blocked. Recent studies have shown that a subset of hepatocellular carcinomas expresses oval cell markers, suggesting that these cells are targets of hepatocarcinogens. However, the signaling pathways that control oval cell activation and proliferation are not well characterized. Based on the role of the nutrient signaling kinase complex, mTORC1, in liver development, we investigated the role of this pathway in oval cell activation. Oval cell proliferation was induced in male Fisher rats by a modification of the traditional choline deficient plus ethionine model (CDE) or by 2-acetylaminoflourene treatment followed by 2/3 partial hepatectomy with or without initiation by diethylnitrosamine. To assess the role of mTOR in the oval cell response and development of preneoplastic foci, the effect of the mTORC1 inhibitor, rapamycin, was studied in all models. Rapamycin induced a significant suppression of the oval cell response in both models, an effect that coincided with a decrease in oval cell proliferation. Rapamycin administration did not affect the abundance of neutrophils or natural killer cells in CDE-treated liver or the expression of key cytokines. Gene expression studies revealed the fetal hepatocyte marker MKP-4 to be expressed in oval cells. In an experimental model of hepatic carcinogenesis, rapamycin decreased the size of preneoplastic foci and the rate of cell proliferation within the foci. mTORC1 signaling plays a key role in the oval cell response and in the development of preneoplastic foci. This pathway may be a target for the chemoprevention of hepatocellular carcinoma.

Topics: Animals; Antibiotics, Antineoplastic; Carcinoma, Hepatocellular; Cell Proliferation; Cell Shape; Cell Transformation, Neoplastic; Choline Deficiency; Diethylnitrosamine; Dual-Specificity Phosphatases; Ethionine; Fluorenes; Gene Expression Profiling; Hepatectomy; Hepatocytes; Liver Neoplasms, Experimental; Male; Mechanistic Target of Rapamycin Complex 1; Mitogen-Activated Protein Kinase Phosphatases; Multiprotein Complexes; Precancerous Conditions; Proteins; Rats; Sirolimus; TOR Serine-Threonine Kinases

Renal transplant recipients (RTR) have a 50-200-fold higher risk for nonmelanoma-skin cancer (NMSC) causing high rates of morbidity and sometimes mortality. Cohort-studies gave evidence that a sirolimus-based immunosuppression may inhibit skin tumor growth. This single-center, prospective, assessor-blinded, randomized trial investigated if switching to sirolimus treatment inhibits the progression of premalignancies and moreover how many new NMSC occur compared to continuation of the original immunosuppressive therapy. Forty-four RTR (mean age 59.9 years, mean duration of immunosuppression 229.5 months) with skin lesions were randomized to sirolimus or continuation of their original immunosuppression. Blinded dermatological assessment at month 6 and 12 by the same dermatologist evaluated the clinical change compared to baseline. Biopsy was performed in suspected malignancy. Already the 6-month-assessment showed significant superiority of sirolimus-therapy: a stop of progression, even regression of preexisting premalignancies (p < 0.0005). This effect was increased at month 12 (p < 0.0001). Nine patients developed histologically confirmed NMSC: one in the sirolimus group, eight in the control group, p = 0.0176. Sirolimus-based immunosuppression in RTR, even when established many years after transplantation, can delay the development of premalignancies, induce regression of preexisting lesions and decelerate the incidence of new NMSC.

Topics: Aged; Carcinoma, Basal Cell; Carcinoma, Squamous Cell; Female; Humans; Immune Tolerance; Immunosuppression Therapy; Immunosuppressive Agents; Kidney Transplantation; Longitudinal Studies; Male; Middle Aged; Precancerous Conditions; Prospective Studies; Sirolimus; Skin Neoplasms

APC mutations cause activation of Wnt/beta-catenin signaling, which invariably leads to colorectal cancer. Similarly, overexpressed Dvl proteins are potent activators of beta-catenin signaling. Screening a large tissue microarray of different staged colorectal tumors by immunohistochemistry, we found that Dvl2 has a strong tendency to be overexpressed in colorectal adenomas and carcinomas, in parallel to nuclear beta-catenin and Axin2 (a universal transcriptional target of Wnt/beta-catenin signaling). Furthermore, deletion of Dvl2 reduced the intestinal tumor numbers in a dose-dependent way in the Apc(Min) model for colorectal cancer. Interestingly, the small intestines of Dvl2 mutants are shortened, reflecting in part a reduction of their crypt diameter and cell size. Consistent with this, mammalian target of rapamycin (mTOR) signaling is highly active in normal intestinal crypts in which Wnt/beta-catenin signaling is active, and activated mTOR signaling (as revealed by staining for phosphorylated 4E-BP1) serves as a diagnostic marker of Apc(Min) mutant adenomas. Inhibition of mTOR signaling in Apc(Min) mutant mice by RAD001 (everolimus) reduces their intestinal tumor load, similarly to Dvl2 deletion. mTOR signaling is also consistently active in human hyperplastic polyps and has a significant tendency for being active in adenomas and carcinomas. Our results implicate Dvl2 and mTOR in the progression of colorectal neoplasia and highlight their potential as therapeutic targets in colorectal cancer.

Topics: Adaptor Proteins, Signal Transducing; Animals; Carrier Proteins; Cell Cycle Proteins; Cell Line, Tumor; Cell Transformation, Neoplastic; Colorectal Neoplasms; Dishevelled Proteins; Eukaryotic Initiation Factors; Everolimus; Female; Humans; Inbreeding; Intestine, Small; Intracellular Signaling Peptides and Proteins; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Phosphoproteins; Phosphorylation; Precancerous Conditions; Protein Serine-Threonine Kinases; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

The increased molecular understanding of cancerous growth may now afford the opportunity to develop novel therapies targeting specific dysregulated molecular mechanisms contributing to the progression of each cancer type. In this regard, the aberrant activation of Akt/mammalian target of rapamycin (mTOR) pathway is a frequent event in head and neck squamous cell carcinomas (HNSCC), thus representing a potential molecular target for the treatment of HNSCC patients. The ability to translate this emerging body of information into effective therapeutic strategies, however, has been hampered by the limited availability of animal models for oral malignancies. Here, we show that the administration in the drinking water to mice of 4-nitroquinoline-1 oxide, a DNA adduct-forming agent that serves as a surrogate of tobacco exposure, leads to the progressive appearance of preneoplastic and tumoral lesions in the tongue and oral mucosa, with 100% incidence after only 16 weeks of carcinogen exposure. Remarkably, many of these lesions evolve spontaneously into highly malignant SCCs few weeks after 4-nitroquinoline-1 oxide withdrawal. In this model, we have observed that the activation of the Akt-mTOR biochemical route represents an early event, which is already detectable in dysplastic lesions. Furthermore, we show that the inhibition of mTOR by the chronic administration of rapamycin halts the malignant conversion of precancerous lesions and promotes the regression of advanced carcinogen-induced SCCs. Together, these findings support the contribution of the mTOR signaling pathway to HNSCC progression and provide a strong rationale for the early evaluation of mTOR inhibitors as a molecular-targeted strategy for HNSCC chemoprevention and treatment.

Topics: 4-Nitroquinoline-1-oxide; Animals; Antibiotics, Antineoplastic; Carcinogens; Carcinoma, Squamous Cell; Cell Transformation, Neoplastic; Disease Progression; Female; Gene Expression; Head and Neck Neoplasms; Immunohistochemistry; Mice; Mice, Inbred C57BL; Precancerous Conditions; Protein Kinases; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

Rapamycin, an inhibitor of mTOR, is in clinical trials for treatment of cancer. Rapamycin resistance has been reported in human breast epithelial tumor cells. Rapamycin effects on mTOR signaling and resistance were examined using benign, premalignant and tumor human breast epithelial cells. Rapamycin inhibition of cell proliferation, the cell cycle and mTOR signaling, including p70S6 and S6RP phosphorylation, was most effective in benign (MCF10A) and premalignant (MCF10AT; MCF10ATG3B) human breast epithelial cells, relative to MCF10CA1a tumor cells. Rapamycin resistance was reflected by reduced inhibition of p70S6K and S6RP phosphorylation in MCF10CA1a tumor cells, with RS6P showing the least response to rapamycin in the tumor cells. Rapamycin differentially inhibited STAT3 phosphorylation in this cell lineage. These data suggest that inhibition of mTOR signaling and STAT3 phosphorylation in benign and premalignant cells may be effective in the treatment of proliferative breast disease (PBD) and in the prevention of tumorigenesis and tumor recurrence.

Topics: Antibiotics, Antineoplastic; Breast; Breast Neoplasms; Cell Cycle; Cell Proliferation; Cells, Cultured; Flow Cytometry; Humans; Immunoblotting; Phosphorylation; Precancerous Conditions; Protein Kinases; Proto-Oncogene Proteins c-akt; Ribosomal Protein S6 Kinases, 70-kDa; Signal Transduction; Sirolimus; STAT1 Transcription Factor; TOR Serine-Threonine Kinases

Rapamycin has been shown to have antitumor effects in various tumor models. To study the effect of rapamycin at different stages of breast cancer development, we used two unique mouse models of breast cancer with activated phosphatidylinositol 3-kinase (PI3K) pathway. Met-1 tumors are highly invasive and metastatic, and mammary intraepithelial neoplasia-outgrowths (MIN-O), a model for human ductal carcinoma in situ, are transplantable premalignant mammary lesions that develop invasive carcinoma with predictable latencies. Both of these models were derived from mammary lesions in Tg(MMTV-PyV-mT) mice.. Met-1 tumors were used to study the effect of rapamycin treatment on invasive disease. Transplanted MIN-O model was used to study the effect of rapamycin on premalignant mammary lesions. Animals were in vivo micro-positron emission tomography imaged to follow the lesion growth and transformation to tumor during the treatment. Cell proliferation, angiogenesis, and apoptosis was assayed by immunohistochemistry.. Rapamycin inhibited in vitro tumor cell proliferation and in vivo Met-1 tumor growth. The growth inhibition was correlated with dephosphorylation of mammalian target of rapamycin (mTOR) targets. Rapamycin treatment significantly reduced the growth of the premalignant MIN-O lesion, as well as tumor incidence and tumor burden. Growth inhibition was associated with reduced cell proliferation and angiogenesis and increased apoptosis.. In PyV-mT mouse mammary models, rapamycin inhibits the growth of premalignant lesions and invasive tumors. Although the inhibitory effect of rapamycin was striking, rapamycin treatment did not completely obliterate the lesions.

Topics: Animals; Antibiotics, Antineoplastic; Antigens, Polyomavirus Transforming; Apoptosis; Carcinoma, Intraductal, Noninfiltrating; Cell Line, Tumor; Cell Proliferation; Dose-Response Relationship, Drug; Female; Male; Mammary Neoplasms, Experimental; Mice; Mice, Transgenic; Phosphatidylinositol 3-Kinases; Phosphorylation; Positron-Emission Tomography; Precancerous Conditions; Protein Kinases; Signal Transduction; Sirolimus; Time Factors; TOR Serine-Threonine Kinases

Amplified in breast cancer 1 (AIB1), an estrogen receptor (ER) coactivator, is frequently amplified or overexpressed in human breast cancer. We previously developed a transgenic mouse model in which AIB1 can act as an oncogene, giving rise to a premalignant hyperplastic mammary phenotype as well as to a high incidence of mammary tumors that are primarily ER(+). In this model, the AIB1 transgene is responsible for continued activation of the insulin-like growth factor-I receptor, suggesting a role for the activation of the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin (mTOR) pathway in the premalignant phenotype and tumor development. Here we show that treatment of AIB1 transgenic mice with the mTOR inhibitor RAD001 reverts the premalignant phenotype. Furthermore, treatment of cell lines derived from AIB1-dependent mammary tumors with RAD001 in culture leads to a G(1) cell cycle arrest. Lastly, tumor growth after injection of ER(+) AIB1 tumor cell lines into wild-type animals is inhibited by RAD001 treatment. In this ER(+) model, inhibition of tumor growth by RAD001 was significantly better than inhibition by the antiestrogen 4-hydroxytamoxifen alone, whereas a combination of both RAD001 and 4-hydroxytamoxifen was most effective. Based on these results, we propose that the combination of mTOR inhibition and ER-targeted endocrine therapy may improve the outcome of the subset of ER(+) breast cancers overexpressing AIB1. These studies provide preclinical support for the clinical development of RAD001 and suggest that AIB1 may be a predictive factor of RAD001 response.

Topics: Animals; Blotting, Western; Cell Proliferation; Cell Survival; Dose-Response Relationship, Drug; Endometrial Hyperplasia; Estrogen Receptor alpha; Everolimus; Female; G1 Phase; Histone Acetyltransferases; Immunohistochemistry; Immunosuppressive Agents; Mammary Neoplasms, Experimental; Mice; Mice, Transgenic; Nuclear Receptor Coactivator 3; Oncogenes; Precancerous Conditions; Protein Kinases; Receptors, Estrogen; Sirolimus; Tamoxifen; TOR Serine-Threonine Kinases; Trans-Activators; Tumor Cells, Cultured

The serine/threonine kinase AKT and its downstream mediator mammalian target of rapamycin (mTOR) are activated in lung adenocarcinoma, and clinical trials are under way to test whether inhibition of mTOR is useful in treating lung cancer. Here, we report that mTOR inhibition blocked malignant progression in K-ras(LA1) mice, which undergo somatic activation of the K-ras oncogene and display morphologic changes in alveolar epithelial cells that recapitulate those of precursors of human lung adenocarcinoma. Levels of phospho-S6(Ser236/235), a downstream mediator of mTOR, increased with malignant progression (normal alveolar epithelial cells to adenocarcinoma) in K-ras(LA1) mice and in patients with lung adenocarcinoma. Atypical alveolar hyperplasia, an early neoplastic change, was prominently associated with macrophages and expressed high levels of phospho-S6(Ser236/235). mTOR inhibition in K-ras(LA1) mice by treatment with the rapamycin analogue CCI-779 reduced the size and number of early epithelial neoplastic lesions (atypical alveolar hyperplasia and adenomas) and induced apoptosis of intraepithelial macrophages. LKR-13, a lung adenocarcinoma cell line derived from K-ras(LA1) mice, was resistant to treatment with CCI-779 in vitro. However, LKR-13 cells grown as syngeneic tumors recruited macrophages, and those tumors regressed in response to treatment with CCI-779. Lastly, conditioned medium from primary cultures of alveolar macrophages stimulated the proliferation of LKR-13 cells. These findings provide evidence that the expansion of lung adenocarcinoma precursors induced by oncogenic K-ras requires mTOR-dependent signaling and that host factors derived from macrophages play a critical role in adenocarcinoma progression.

Topics: Adenocarcinoma; Adenoma; Animals; Cell Line, Tumor; Cell Transformation, Neoplastic; Disease Progression; Enzyme Activation; Genes, ras; Hyperplasia; Lung Neoplasms; Macrophages, Alveolar; Mice; Mutation; Precancerous Conditions; Protein Kinase Inhibitors; Protein Kinases; Protein Serine-Threonine Kinases; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-akt; Pulmonary Alveoli; Ribosomal Protein S6 Kinases; Sirolimus; TOR Serine-Threonine Kinases

Functional inactivation of tuberous sclerosis 2 gene (Tsc2) leads to renal carcinogenesis in the hereditary renal carcinoma Eker rat models. Recent studies revealed a role of tuberin, a TSC2 product, in suppressing the p70 S6 kinase (p70S6K) activity via inhibition of mammalian target of rapamycin (mTOR). Phosphorylated S6 protein, a substrate of p70S6K, was expressed in the early lesions in Eker rats, and this expression was suppressed by the treatment of rapamycin, an inhibitor of mTOR. We previously isolated the novel gene Niban expressed in renal carcinogenesis of Eker rats. In this study, we demonstrated that the expression of Niban was detected from early preneoplastic lesions in Eker rats. Interestingly, in contrast to the phosphorylated S6 protein, the expression of Niban was unchanged and early lesions still remained even after treatment with rapamycin. These results might suggest the existence of another pathway independent of mTOR-S6K pathway in Tsc2 mutant renal carcinogenesis. In addition, Niban was also expressed in other renal carcinoma models, including Tsc1 and Tsc2 knockout mice, and various types of human renal cell carcinomas. Thus, Niban was commonly expressed in renal carcinomas and might be a new marker for renal carcinogenesis.

Topics: Amino Acid Sequence; Animals; Biomarkers, Tumor; Cell Line, Tumor; Gene Expression Regulation, Neoplastic; Humans; Immunohistochemistry; Kidney Neoplasms; Mice; Molecular Sequence Data; Phosphorylation; Precancerous Conditions; Rats; Repressor Proteins; Ribosomal Protein S6 Kinases; Sirolimus; Tuberous Sclerosis Complex 2 Protein; Tumor Suppressor Proteins