Cancer progression as a sequence of atavistic reversions.

It has long been recognized that cancer onset and progression represent a type of reversion to an ancestral quasi-unicellular phenotype. This general concept has been refined into the atavistic model of cancer that attempts to provide a quantitative analysis and testable predictions based on genomic data. Over the past decade, support for the multicellular-to-unicellular reversion predicted by the atavism model has come from phylostratigraphy. Here, we propose that cancer onset and progression involve more than a one-off multicellular-to-unicellular reversion, and are better described as a series of reversionary transitions. We make new predictions based on the chronology of the unicellular-eukaryote-to-multicellular-eukaryote transition. We also make new predictions based on three other evolutionary transitions that occurred in our lineage: eukaryogenesis, oxidative phosphorylation and the transition to adaptive immunity. We propose several modifications to current phylostratigraphy to improve age resolution to test these predictions. Also see the video abstract here: https://youtu.be/3unEu5JYJrQ.

The therapeutic potential of RNA Polymerase I transcription inhibitor, CX-5461, in uterine leiomyosarcoma.

BACKGROUND: Uterine leiomyosarcoma is a rare aggressive smooth muscle cancer with poor survival rates. RNA Polymerase I (Pol I) activity is elevated in many cancers supporting tumour growth and prior studies in uterine leiomyosarcoma revealed enlarged nucleoli and upregulated Pol I activity-related genes. This study aimed to investigate the anti-tumour potential of CX-5461, a Pol I transcription inhibitor currently being evaluated in clinical trials for several cancers, against the human uterine leiomyosarcoma cell line, SK-UT-1. METHODS: SK-UT-1 was characterised using genome profiling and western blotting. The anti-tumour effects of CX-5461 were investigated using cell proliferation assays, expression analysis using qRT-PCR, and BrdU/PI based cell cycle analysis. RESULTS: Genetic analysis of SK-UT-1 revealed mutations in TP53, RB1, PTEN, APC and TSC1 & 2, all potentially associated with increased Pol I activity. Protein expression analysis showed dysregulated p53, RB1 and c-Myc. CX-5461 treatment resulted in an anti-proliferation response, G2 phase cell-cycle arrest and on-target activity demonstrated by reduced ribosomal DNA transcription. CONCLUSIONS: SK-UT-1 was confirmed as a representative model of uterine leiomyosarcoma and CX-5461 has significant potential as a novel adjuvant for this rare cancer.

Potential contrasting effects of platelets on the migration and invasion of sarcomas versus carcinomas.

The ability of platelets to promote carcinoma and melanoma progression has been thoroughly studied and occurs in numerous ways. In contrast, the effect of platelets on sarcomas, tumors arising from mesenchymal cells, has received very little attention. This study was undertaken to simultaneously compare the effects of platelets on murine and human sarcomas and carcinomas. In contrast to their effect on carcinomas, platelets inhibited the invasion of some murine- and all human sarcomas tested in vitro. Further invasion studies with TGFß treatment only partially recapitulated the results seen with whole platelets. In a spontaneous tumor growth and lung metastasis model, platelets promoted 4T1 mammary carcinoma metastasis but not MCA-1 fibrosarcoma metastasis. Gene expression analysis of the platelet-promoted MDA-MB-231 breast carcinoma, and the platelet-inhibited HT1080 fibrosarcoma cell lines revealed that exposure of MDA-MB-231 to platelets, resulted in upregulation of oncogenes and EMT-associated genes whereas in HT1080 a tumor-suppressor gene was significantly upregulated. Thus, this study has revealed a potential diametrically opposing effect of platelets on mesenchymal and epithelial cancers, a finding that warrants further investigation.

Dichloroacetate Prevents Cisplatin-Induced Nephrotoxicity without Compromising Cisplatin Anticancer Properties.

Cisplatin is an effective anticancer drug; however, cisplatin use often leads to nephrotoxicity, which limits its clinical effectiveness. In this study, we determined the effect of dichloroacetate, a novel anticancer agent, in a mouse model of cisplatin-induced AKI. Pretreatment with dichloroacetate significantly attenuated the cisplatin-induced increase in BUN and serum creatinine levels, renal tubular apoptosis, and oxidative stress. Additionally, pretreatment with dichloroacetate accelerated tubular regeneration after cisplatin-induced renal damage. Whole transcriptome sequencing revealed that dichloroacetate prevented mitochondrial dysfunction and preserved the energy-generating capacity of the kidneys by preventing the cisplatin-induced downregulation of fatty acid and glucose oxidation, and of genes involved in the Krebs cycle and oxidative phosphorylation. Notably, dichloroacetate did not interfere with the anticancer activity of cisplatin in vivo. These data provide strong evidence that dichloroacetate preserves renal function when used in conjunction with cisplatin.

Testosterone regulation of cyclin E kinase: A key factor in determining gender differences in hepatocarcinogenesis.

BACKGROUND AND AIM: While gender differences in hepatocellular carcinoma (HCC) are profound, the mechanism is unclear. Using castration and hormone replacement strategies, we tested whether these gender differences are attributable to testosterone or estradiol/progesterone effects on cell cycle regulators and p53. METHODS: We studied dysplastic liver and HCCs in intact and castrated diethylnitrosamine-injected C57BL/6J male and female mice, with or without hormonal replacement. Effects of sex steroids on proliferation and survival of primary hepatocytes and primary HCC cells were also characterized. RESULTS: Diethylnitrosamine-injected female mice displayed fewer dysplastic foci and slower onset of HCC than male mice, with smaller/more differentiated tumors and fewer metastases. Castration of diethylnitrosamine-injected male mice reduced cyclin E kinase and augmented hepatocyte apoptosis compared with intact male mice; estradiol/progesterone enhanced these effects. In intact female mice, cyclin E kinase activity was less than in males; testosterone administered to ovariectomized female mice upregulated cyclin E, increased cyclin E kinase, and accelerated hepatocarcinogenesis. In vitro, testosterone increased expression of cell cycle regulators (cyclin D1, cyclin E, and cyclin-dependent kinase 2) and reduced p53 and p21, which enhanced hepatocyte viability. In contrast, estradiol both suppressed hepatocyte cell cycle markers, upregulated p53 and reduced viability of hepatocytes and HCC cells. CONCLUSIONS: Testosterone is the positive regulator of hepatocyte cell cycle via cyclin E, while estradiol plays a negative role by effects of p53 and p21. Together, both sex hormones determine the male predominance of gender differences in hepatocarcinogenesis.

Targeting RNA Polymerase I Transcription Activity in Osteosarcoma: Pre-Clinical Molecular and Animal Treatment Studies.

The survival rate of patients with osteosarcoma (OS) has not improved over the last 30 years. Mutations in the genes TP53, RB1 and c-Myc frequently occur in OS and enhance RNA Polymerase I (Pol I) activity, thus supporting uncontrolled cancer cell proliferation. We therefore hypothesised that Pol I inhibition may be an effective therapeutic strategy for this aggressive cancer. The Pol I inhibitor CX-5461 has demonstrated therapeutic efficacy in different cancers in pre-clinical and phase I clinical trials; thus, the effects were determined on ten human OS cell lines. Following characterisation using genome profiling and Western blotting, RNA Pol I activity, cell proliferation and cell cycle progression were evaluated in vitro, and the growth of TP53 wild-type and mutant tumours was measured in a murine allograft model and in two human xenograft OS models. CX-5461 treatment resulted in reduced ribosomal DNA (rDNA) transcription and Growth 2 (G2)-phase cell cycle arrest in all OS cell lines. Additionally, tumour growth in all allograft and xenograft OS models was effectively suppressed without apparent toxicity. Our study demonstrates the efficacy of Pol I inhibition against OS with varying genetic alterations. This study provides pre-clinical evidence to support this novel therapeutic approach in OS.

Map making in the 21st century: charting breast cancer susceptibility pathways in rodent models.

Genetic factors play an important role in determining risk and resistance to increased breast cancer. Recent technological advances have made it possible to analyze hundreds of thousands of single nucleotide polymorphisms in large-scale association studies in humans and have resulted in identification of alleles in over 20 genes that influence breast cancer risk. Despite these advances, the challenge remains in identifying what the functional polymorphisms are that confer the increased risk, and how these genetic variants interact with each other and with environmental factors. In rodents, the incidence of mammary tumors varies among strains, such that they can provide alternate ideas for candidate pathways involved in humans. Mapping studies in animals have unearthed numerous loci for breast cancer susceptibility that have been validated in human populations. In a reciprocal manner, knockin and knockout mice have been used to validate the tumorigenicity of risk alleles found in population studies. Rodent studies also underscore the complexity of interactions among alleles. The fact that genes affecting risk and resistance to mammary tumors in rodents depend greatly upon the carcinogenic challenge emphasizes the importance of gene x environment interactions. The challenge to rodent geneticists now is to capitalize on the ability to control the genetics and environment in rodent models of tumorigenesis to better understand the biology of breast cancer development, to identify those polymorphisms most relevant to human susceptibility and to identify compensatory pathways that can be targeted for improved prevention in women at highest risk of developing breast cancer.

Rats: gnawing through the barriers to understanding genetic susceptibility and breast cancer.

Advances in genotyping technology have provided us with a large number of genetic loci associated with cancer susceptibility; however, our ability to understand the functional effects of the genetic variants of these loci remains limited. In the previous issue, Smits and colleagues demonstrate the use of congenic rat strains to discover that the Mcs5a breast cancer susceptibility locus is most likely acting through the immune system, via novel transcriptional regulatory mechanisms. This challenges our conventional thinking of cancer susceptibility and gene regulation pathways, and illustrates the potential for rodent models to help us functionally characterize polymorphisms of cancer-associated loci.

Glutathione transferase kappa deficiency causes glomerular nephropathy without overt oxidative stress.

Glutathione transferase kappa (GSTK1-1) is a highly conserved, mitochondrial enzyme potentially involved in redox reactions. GSTK1-1-deficient mice were generated to further study the enzyme's biological role. Reduced and total glutathione levels in liver and kidney were unchanged by GSTK1-1 deficiency and NADPH quinone oxidoreductase 1 expression was not elevated indicating that there is no general underlying oxidative stress in Gstk1(-/-) mice. Electron microscopy of liver and kidney showed no changes in mitochondrial morphology with GSTK1-1 deficiency. The death of a number of Gstk1(-/-) males with urinary tract problems prompted close examination of the kidneys. Electron microscopy revealed glomerular basement membrane changes at 3 months, accompanied by detectable microalbuminuria in male mice (albumin:creatinine ratio of 2.66±0.83 vs 1.13±0.20 mg/mmol for Gstk1(-/-) and wild-type (WT), respectively, P=0.001). This was followed by significant foot process effacement (40-55% vs 10% for Gstk1(-/-) and WT, respectively) at 6 months of age in all Gstk1(-/-) mice examined. Kidney tubules were ultrastructurally normal. Compared with human disease, the Gstk1(-/-) kidneys show changes seen in glomerulopathies causing nephrotic syndrome. Gstk1(-/-) mice may offer insights into the early development of glomerular nephropathies.

Targeting metabolism with arsenic trioxide and dichloroacetate in breast cancer cells.

BACKGROUND: Cancer cells have a different metabolic profile compared to normal cells. The Warburg effect (increased aerobic glycolysis) and glutaminolysis (increased mitochondrial activity from glutamine catabolism) are well known hallmarks of cancer and are accompanied by increased lactate production, hyperpolarized mitochondrial membrane and increased production of reactive oxygen species. METHODS: In this study we target the Warburg effect with dichloroacetate (DCA) and the increased mitochondrial activity of glutaminolysis with arsenic trioxide (ATO) in breast cancer cells, measuring cell proliferation, cell death and mitochondrial characteristics. RESULTS: The combination of DCA and ATO was more effective at inhibiting cell proliferation and inducing cell death than either drug alone. We examined the effect of these treatments on mitochondrial membrane potential, reactive oxygen species production and ATP levels and have identified new molecular mechanisms within the mitochondria for both ATO and DCA: ATO reduces mitochondrial function through the inhibition of cytochrome C oxidase (complex IV of the electron transport chain) while DCA up-regulates ATP synthase ß subunit expression. The potentiation of ATO cytotoxicity by DCA is correlated with strong suppression of the expression of c-Myc and HIF-1α, and decreased expression of the survival protein Bcl-2. CONCLUSION: This study is the first to demonstrate that targeting two key metabolic hallmarks of cancer is an effective anti-cancer strategy with therapeutic potential.

Pathways contributing to development of spontaneous mammary tumors in BALB/c-Trp53+/- mice.

Mutation and loss of function in p53 are common features among human breast cancers. Here we use BALB/c-Trp53+/- mice as a model to examine the sequence of events leading to mammary tumors. Mammary gland proliferation rates were similar in both BALB/c-Trp53+/- mice and wild-type controls. In addition, sporadic mammary hyperplasias were rare in BALB/c-Trp53+/- mice and not detectably different from those of wild-type controls. Among the 28 mammary tumors collected from BALB/c-Trp53+/- mice, loss of heterozygosity for Trp53 was detected in more than 90% of invasive mammary tumors. Transplantation of Trp53+/- ductal hyperplasias also indicated an association between loss of the wild-type allele of Trp53 and progression to invasive carcinomas. Therefore, loss of p53 function seems to be a rate-limiting step in progression. Moreover, expression of biomarkers such as estrogen receptor alpha, progesterone receptor, Her2/Neu, and activated Notch1 varied among mammary tumors, suggesting that multiple oncogenic lesions collaborate with loss of p53 function. Expression of biomarkers was retained when tumor fragments were transplanted to syngeneic hosts. Tumors expressing solely luminal or basal keratins were also observed (27 and 11%, respectively), but the largest class of tumors expressed both luminal and basal keratins (62%). Overall, this panel of transplantable tumors provides a resource for detailed evaluation of the cell lineages undergoing transformation and preclinical testing of therapeutic agents targeting a variety of oncogenic pathways including cancer stem cells.

Genetic modifiers regulating DNA replication and double-strand break repair are associated with differences in mammary tumors in mouse models of Li-Fraumeni syndrome.

Breast cancer is the most common tumor among women with inherited variants in the TP53 tumor suppressor, but onset varies widely suggesting interactions with genetic or environmental factors. Rodent models haploinsufficent for Trp53 also develop a wide variety of malignancies associated with Li-Fraumeni syndrome, but BALB/c mice are uniquely susceptible to mammary tumors and is genetically linked to the Suprmam1 locus on chromosome 7. To define mechanisms that interact with deficiencies in p53 to alter susceptibility to mammary tumors, we fine mapped the Suprmam1 locus in females from an N2 backcross of BALB/cMed and C57BL/6J mice. A major modifier was localized within a 10 cM interval on chromosome 7. The effect of the locus on DNA damage responses was examined in the parental strains and mice that are congenic for C57BL/6J alleles on the BALB/cMed background (SM1-Trp53+/-). The mammary epithelium of C57BL/6J-Trp53+/- females exhibited little radiation-induced apoptosis compared to BALB/cMed-Trp53+/- and SM1-Trp53+/- females indicating that the Suprmam1B6/B6 alleles could not rescue repair of radiation-induced DNA double-strand breaks mostly relying on non-homologous end joining. In contrast, the Suprmam1B6/B6 alleles in SM1-Trp53+/- mice were sufficient to confer the C57BL/6J-Trp53+/- phenotypes in homology-directed repair and replication fork progression. The Suprmam1B6/B6 alleles in SM1-Trp53+/- mice appear to act in trans to regulate a panel of DNA repair and replication genes which lie outside the locus.

Reversal of the glycolytic phenotype by dichloroacetate inhibits metastatic breast cancer cell growth in vitro and in vivo.

The glycolytic phenotype is a widespread phenomenon in solid cancer forms, including breast cancer. Dichloroacetate (DCA) has recently been proposed as a novel and relatively non-toxic anti-cancer agent that can reverse the glycolytic phenotype in cancer cells through the inhibition of pyruvate dehydrogenase kinase. We have examined the effect of DCA against breast cancer cells, including in a highly metastatic in vivo model. The growth of several breast cancer cell lines was found to be inhibited by DCA in vitro. Further examination of 13762 MAT rat mammary adenocarcinoma cells found that reversal of the glycolytic phenotype by DCA correlated with the inhibition of proliferation without any increase in cell death. This was despite a small but significant increase in caspase 3/7 activity, which may sensitize cancer cells to other apoptotic triggers. In vivo, DCA caused a 58% reduction in the number of lung metastases observed macroscopically after injection of 13762 MAT cells into the tail vein of rats (P = 0.0001, n > or = 9 per group). These results demonstrate that DCA has anti-proliferative properties in addition to pro-apoptotic properties, and can be effective against highly metastatic disease in vivo, highlighting its potential for clinical use.

GSTZ1 genotypes correlate with dichloroacetate pharmacokinetics and chronic side effects in multiple myeloma patients in a pilot phase 2 clinical trial.

Dichloroacetate (DCA) is an investigational drug targeting the glycolytic hallmark of cancer by inhibiting pyruvate dehydrogenase kinases (PDK). It is metabolized by GSTZ1, which has common polymorphisms altering enzyme or promoter activity. GSTZ1 is also irreversibly inactivated by DCA. In the first clinical trial of DCA in a hematological malignancy, DiCAM (DiChloroAcetate in Myeloma), we have examined the relationship between DCA concentrations, GSTZ1 genotype, side effects, and patient response. DiCAM recruited seven myeloma patients in partial remission. DCA was administered orally for 3 months with a loading dose. Pharmacokinetics were performed on day 1 and 8. Trough and peak concentrations of DCA were measured monthly. GSTZ1 genotypes were correlated with drug concentrations, tolerability, and disease outcomes. One patient responded and two patients showed a partial response after one month of DCA treatment, which included the loading dose. The initial half-life of DCA was shorter in two patients, correlating with heterozygosity for GSTZ1*A genotype, a high enzyme activity variant. Over 3 months, one patient maintained DCA trough concentrations approximately threefold higher than other patients, which correlated with a low activity promoter genotype (-1002A, rs7160195) for GSTZ1. This patient displayed the strongest response, but also the strongest neuropathy. Overall, serum concentrations of DCA were sufficient to inhibit the constitutive target PDK2, but unlikely to inhibit targets induced in cancer. Promoter GSTZ1 polymorphisms may be important determinants of DCA concentrations and neuropathy during chronic treatment. Novel dosing regimens may be necessary to achieve effective DCA concentrations in most cancer patients while avoiding neuropathy.

The SuprMam1 breast cancer susceptibility locus disrupts the vitamin D/ calcium/ parathyroid hormone pathway and alters bone structure in congenic mice.

Breast cancer is a complex disease, and approximately 30% of cases are considered to be hereditary or familial, with a large fraction of this being polygenic. However, it is difficult to demonstrate the functional importance of genes of small effect in population studies, and these genes are not always easily targeted for prevention. The SuprMam (suppressor of mammary tumour) breast cancer susceptibility alleles were previously identified as contributors to spontaneous mammary tumour development in Trp53+/- mice. In this study, we have generated and characterised congenic mice that contain the BALB/c SuprMam1 (susceptibility) locus on a C57BL/6 (resistant) background and discovered a subtle impairment in the vitamin D/ calcium/ parathyroid hormone (PTH) pathway. This was evident as altered gene expression in the mammary glands of key players in this pathway. Further functional analysis of the mice revealed elevated PTH levels, reduced Cyp27b1 expression in kidneys, and reduced trabecular bone volume/ tissue volume percentage. Plasma 25(OH)D and serum calcium were unchanged. This impairment was a result of genetic differences and occurred only in females, but the elevated PTH levels could be overcome with either calcium or vitamin D dietary supplementation. Either low levels of active vitamin D (1,25(OH)2D) or chronically elevated PTH levels may contribute to increased breast cancer susceptibility. These indicators are not easily measured in human population studies, but either mechanism may be preventable with dietary calcium or vitamin D supplements. Therefore, SuprMam congenic mice could serve as a valuable model for studying the role of gene-hormone-environment interactions of the vitamin D/ calcium/ PTH pathway in cancer and other diseases and for testing preventive interventions.

Deletion of Glu155 causes a deficiency of glutathione transferase Omega 1-1 but does not alter sensitivity to arsenic trioxide and other cytotoxic drugs.

The Omega class glutathione transferase GSTO1-1 can catalyze the reduction of pentavalent methylated arsenic species and is responsible for the biotransfomation of potentially toxic alpha-haloketones. We investigated the cause of GSTO1-1 deficiency in the T-47D breast cancer cell line and found that the cell line is hemizygous for a polymorphic allele that encodes the deletion of Glu155. Northern and Western blots show that T-47D cells contain GSTO1 mRNA but no GSTO1-1 protein suggesting that the deletion of Glu155 causes GSTO1-1 deficiency in vivo. In further support of this contention we found that lymphoblastoid cell lines from subjects who are heterozygous for the deletion of Glu155 have only 60% of normal activity with the GSTO1-1 specific substrate 4-nitrophenacyl glutathione. Pulse-chase studies showed that the deletion of Glu155 causes increased turnover of GSTO1-1 in T47-D cells. These data establish the fact that the polymorphic deletion of Glu155 can cause GSTO1-1 deficiency in vivo. GSTO1-1 expression is elevated in some cell lines that are resistant to the cytotoxic cancer drugs adriamycin, etoposide and cisplatinum but its specific contribution to multi drug resistance has not been evaluated. In this study GSTO1-1 deficient T47-D cells were used to determine if GSTO1-1 contributes directly to arsenic and drug resistance. We established stable expression of normal GSTO1-1 in T-47D cells and found that this did not alter sensitivity to arsenic trioxide, cisplatinum daunorubicin or etoposide.

Estrogen and progesterone induce persistent increases in p53-dependent apoptosis and suppress mammary tumors in BALB/c-Trp53+/- mice.

INTRODUCTION: Treatment with estrogen and progesterone (E+P) mimics the protective effect of parity on mammary tumors in rodents and depends upon the activity of p53. The following experiments tested whether exogenous E+P primes p53 to be more responsive to DNA damage and whether these pathways confer resistance to mammary tumors in a mouse model of Li-Fraumeni syndrome. METHODS: Mice that differ in p53 status (Trp53+/+, Trp53+/-, Trp53-/-) were treated with E+P for 14 days and then were tested for p53-dependent responses to ionizing radiation. Responses were also examined in parous and age-matched virgins. The effects of hormonal exposures on tumor incidence were examined in BALB/c-Trp53+/- mammary tissues. RESULTS: Nuclear accumulation of p53 and apoptotic responses were increased similarly in the mammary epithelium from E+P-treated and parous mice compared with placebo and age-matched virgins. This effect was sustained for at least 7 weeks after E+P treatment and did not depend on the continued presence of ovarian hormones. Hormone stimulation also enhanced apoptotic responses to ionizing radiation in BALB/c-Trp53+/- mice but these responses were intermediate compared with Trp53+/+ and Trp-/- tissues, indicating haploinsufficiency. The appearance of spontaneous mammary tumors was delayed by parity in BALB/c-Trp53+/- mice. The majority of tumors lacked estrogen receptor (ER), but ER+ tumors were observed in both nulliparous and parous mice. However, apoptotic responses to ionizing radiation and tumor incidence did not differ among outgrowths of epithelial transplants from E+P-treated donors and nulliparous donors. CONCLUSION: Therefore, E+P and parity confer a sustained increase in p53-mediated apoptosis within the mammary epithelium and suppress mammary tumorigenesis, but this effect was not retained in epithelial outgrowths.

Long-term stabilization of metastatic melanoma with sodium dichloroacetate.

Sodium dichloroacetate (DCA) has been studied as a metabolic cancer therapy since 2007, based on a publication from Bonnet et al demonstrating that DCA can induce apoptosis (programmed cell death) in human breast, lung and brain cancer cells. Classically, the response of cancer to a medical therapy in human research is measured by Response Evaluation Criterial for Solid Tumours definitions, which define "response" by the degree of tumour reduction, or tumour disappearance on imaging, however disease stabilization is also a beneficial clinical outcome. It has been shown that DCA can function as a cytostatic agent in vitro and in vivo, without causing apoptosis. A case of a 32-year-old male is presented in which DCA therapy, with no concurrent conventional therapy, resulted in regression and stabilization of recurrent metastatic melanoma for over 4 years' duration, with trivial side effects. This case demonstrates that DCA can be used to reduce disease volume and maintain long-term stability in patients with advanced melanoma.

Leptin signals via TGFB1 to promote metastatic potential and stemness in breast cancer.

Epidemiological studies have shown obesity to be linked with poorer outcomes in breast cancer patients. The molecular mechanisms responsible for the increased risk of invasive/metastatic disease with obesity are complex, but may include elevated levels of adipokines such as leptin. Using physiological levels of leptin found in obesity in a novel chronic in vitro treatment model (≤200 ng/ml for 14 days), we confirmed the occurrence of leptin-mediated changes in growth, apoptosis and metastatic behavior, and gene expression changes representing epithelial-to-mesenchymal transition (EMT) and a cancer stem cell (CSC) like phenotype in breast epithelial and cancer cell lines (MCF10A, MCF10AT1, MCF7 and MDA-MB-231). Further, we have discovered that these effects were accompanied by increased expression of TGFB1, and could be significantly reduced by co-treatment with neutralizing antibody against TGFB1, indicating that the induction of these characteristics was mediated via TGFB1. Occurring in both MCF7 and MCF10AT1 cells, it suggests these actions of leptin to be independent of estrogen receptor status. By linking leptin signalling to the established TGFB1 pathway of metastasis / EMT, this study gives a direct mechanism by which leptin can contribute to the poorer outcomes of obese cancer patients. Inhibitors of TGFB1 are in currently in phase III clinical trials in other malignancies, thus identifying the connection between leptin and TGFB1 will open new therapeutic opportunities for improving outcomes for obese breast cancer patients.

BALB/c alleles for Prkdc and Cdkn2a interact to modify tumor susceptibility in Trp53+/- mice.

In mice heterozygous for p53 (Trp53(+/-)), the incidence of mammary tumors varies among strains, with C57BL/6 being resistant and BALB/c being susceptible. Mammary tumor phenotypes were examined in female Trp53(+/-) F1 mice (C57BL/6 x BALB/c;n = 19) and N2 backcross mice [(C57BL/6 x BALB/c) x BALB/c] (n = 224). Susceptibility to mammary tumors segregated as a dominant phenotype in F1 females, but a higher frequency and shorter latency in N2 mice indicated a contribution from recessive-acting modifiers. Segregation of the hypomorphic BALB/c alleles for DNA-dependent protein kinase catalytic subunit (Prkdc) and p16(INK4A) (Cdkn2a) was analyzed in the N2 mice. The time to first tumor (considering all tumor types) was significantly different among the four genotype combinations (P = 0.01). Cdkn2a had a strong effect (P = 0.008) but was restricted to Prkdc(B/B) mice (P = 0.001), indicating a strong interaction between the loci. Differences in mammary tumor occurrence among genotypes for Prkdc and Cdkn2a in N2 mice were not statistically significant. This study indicates that BALB/c Prkdc and Cdkn2a alleles do modify tumor incidence in Trp53(+/-) mice and highlights the complexity of gene interaction effects in determining cancer phenotypes but discounts these alleles as major recessive loci contributing to spontaneous mammary tumor susceptibility.