Prolactin synergizes with canonical Wnt signals to drive development of ER+ mammary tumors via activation of the Notch pathway.

Prolactin (PRL) cooperates with other factors to orchestrate mammary development and lactation, and is epidemiologically linked to higher risk for breast cancer. However, how PRL collaborates with oncogenes to foster tumorigenesis and influence breast cancer phenotype is not well understood. To understand its interactions with canonical Wnt signals, which elevate mammary stem cell activity, we crossed heterozygous NRL-PRL mice with ApcMin/+ mice and treated pubertal females with a single dose of mutagen. PRL in the context of ApcMin/+ fueled a dramatic increase in tumor incidence in nulliparous mice, compared to ApcMin/+ alone. Although carcinomas in both NRL-PRL/ApcMin/+ and ApcMin/+ females acquired a mutation in the remaining wildtype Apc allele and expressed abundant ß-catenin, PRL-promoted tumors displayed higher levels of Notch-driven target genes and Notch-dependent cancer stem cell activity, compared to ß-catenin-driven activity in ApcMin/+ tumors. This PRL-induced shift to dominant Notch signals was evident in preneoplastic epithelial hyperplasias at 120 days of age. In NRL-PRL/ApcMin/+ females, rapidly proliferating hyperplasias, characterized by ß-catenin at cell junctions and high NOTCH1 expression, contrasted with slower growing lesions with nuclear ß-catenin in ApcMin/+ females. These studies demonstrate that PRL can powerfully modulate the incidence and phenotype of mammary tumors, shedding light on mechanisms whereby PRL elevates risk of breast cancer.

High rates of chromosome missegregation suppress tumor progression but do not inhibit tumor initiation.

Aneuploidy, an abnormal chromosome number that deviates from a multiple of the haploid, has been recognized as a common feature of cancers for >100 yr. Previously, we showed that the rate of chromosome missegregation/chromosomal instability (CIN) determines the effect of aneuploidy on tumors; whereas low rates of CIN are weakly tumor promoting, higher rates of CIN cause cell death and tumor suppression. However, whether high CIN inhibits tumor initiation or suppresses the growth and progression of already initiated tumors remained unclear. We tested this using the Apc(Min/+) mouse intestinal tumor model, in which effects on tumor initiation versus progression can be discriminated. Apc(Min/+) cells exhibit low CIN, and we generated high CIN by reducing expression of the kinesin-like mitotic motor protein CENP-E. CENP-E(+/-);Apc(Min/+) doubly heterozygous cells had higher rates of chromosome missegregation than singly heterozygous cells, resulting in increased cell death and a substantial reduction in tumor progression compared with Apc(Min/+) animals. Intestinal organoid studies confirmed that high CIN does not inhibit tumor cell initiation but does inhibit subsequent cell growth. These findings support the conclusion that increasing the rate of chromosome missegregation could serve as a successful chemotherapeutic strategy.

Prevalence of ATM Sequence Variants in Northern Plains American Indian Cancer Patients.

PURPOSE: To identify sequence variants of the ataxia telangiectasia mutated (ATM) gene and establish their prevalence rate among American Indian (AI) as compared with non-AI cancer patients. MATERIALS AND METHODS: DNA was isolated from blood samples collected from 100 AI and 100 non-AI cancer patients undergoing radiation therapy, and a blinded assessment of the ATM sequence was conducted. Quantitative PCR assessment of copy number for each exon was also performed. The main outcome measure was the prevalence of ATM variants in the two patient populations. RESULTS: No statistically significant differences for total prevalence of ATM variants among AI and non-AI patients were found. Of the 25 variants identified, 5 variants had a prevalence of >2%, of which 4 occurred at a rate of >5% in one or both groups. The prevalence of these four variants could meaningfully be compared between the two groups. The only statistically significant difference among the groups was the c.4138C > T variant which is predicted not to affect protein function, seen in 8% of AI versus 0% of non-AI patients (P = 0.007). No exonic copy number changes were found in these patients. CONCLUSION: This study is the first to determine the prevalence of ATM variants in AIs.

Quantitative trait loci associated with susceptibility to bladder and kidney infections induced by Escherichia coli in female C3H/HeJ mice.

BACKGROUND: The C3H/HeJ mouse strain develops severe bladder and kidney infections after receiving intravesical inoculation with uropathogenic Escherichia coli. This susceptibility is genetically determined, but the specific genes involved have not been completely defined. The objective of the present study was to use quantitative trait locus (QTL) mapping to identify chromosomal sites associated with susceptibility to infection in C3H/HeJ mice. METHODS: Female mice from a backcross of C3H/HeJ and (BALB/cxC3H/HeJ)F1 mice were inoculated with E. coli, and the number of E. coli colony-forming units present in the bladder and kidneys was quantified 10 days later. Genomic DNA was scanned using microsatellite markers to localize chromosomal segments derived from parental strains. Statistical analyses associated infection phenotypes with chromosomal sites. RESULTS: A highly significant QTL for susceptibility to bladder infection was identified on chromosome 4, and C3H/HeJ alleles at this locus interacted with BALB/c alleles on chromosome 19 to increase the severity of infection. A significant QTL on chromosome 6 was associated with severe kidney infections. CONCLUSIONS: Increased susceptibility to E. coli bladder and kidney infections in female C3H/HeJ mice is associated with specific chromosomal sites located near genes contributing to host resistance to infection. The results demonstrate the multigenic nature of susceptibility to urinary tract infections.

Up-regulation of fibroblast growth factor-binding protein, by beta-catenin during colon carcinogenesis.

Fibroblast growth factor-binding protein (FGF-BP) releases immobilized FGFs from the extracellular matrix and can function as an angiogenic switch molecule in cancer. Here we show that FGF-BP is up-regulated in early dysplastic lesions of the human colon that are typically associated with a loss of adenomatous polyposis coli and up-regulation of beta-catenin. In addition, FGF-BP expression is induced in dysplastic lesions in ApcMin/+ mice in parallel with the up-regulation of beta-catenin. Also, in cell culture studies FGF-BP is induced by beta-catenin through direct activation of the FGF-BP gene promoter. We conclude that FGF-BP is a target gene of beta-catenin.

Pathway pathology: histological differences between ErbB/Ras and Wnt pathway transgenic mammary tumors.

To study phenotype-genotype correlations, ErbB/Ras pathway tumors (transgenic for ErbB2, c-Neu, mutants of c-Neu, polyomavirus middle T antigene (PyV-mT), Ras, and bi-transgenic for ErbB2/Neu with ErbB3 and with progesterone receptor) from four different institutions were histopathologically compared with Wnt pathway tumors [transgenes Wnt1, Wnt10b, dominant-negative glycogen synthase kinase 3-beta, beta-Catenin, and spontaneous mutants of adenomatous polyposis coli gene (Apc)]. ErbB/Ras pathway tumors tend to form solid nodules consisting of poorly differentiated cells with abundant cytoplasm. ErbB/Ras pathway tumors also have scanty stroma and lack myoepithelial or squamous differentiation. In contrast, Wnt pathway tumors exhibit myoepithelial, acinar, or glandular differentiation, and, frequently, combinations of these. Squamous metaplasia is frequent and may include transdifferentiation to epidermal and pilar structures. Most Wnt pathway tumors form caricatures of elongated, branched ductules, and have well-developed stroma, inflammatory infiltrates, and pushing margins. Tumors transgenic for interacting genes such as protein kinase CK2alpha (casein kinase IIalpha), and the fibroblast growth factors (Fgf) Int2/Fgf3 or keratinocyte growth factor (Kgf/Fgf7) also have the Wnt pathway phenotype. Because the tumors from the ErbB/Ras and the Wnt pathway are so distinct and can be readily identified using routine hematoxylin and eosin sections, we suggest that pathway pathology is applicable in both basic and clinical cancer research.