Abstract 3050: Polymorphisms in the arntl2 promoter affect breast cancer metastasis susceptibility

Breast cancer mortality is primarily due to metastatic lesions rather than primary tumors, yet relatively little is known regarding the mechanisms of metastatic breast cancer, making it difficult to identify patients who are at risk for metastatic disease. Our hypothesis suggests that inherited germline mutations contribute to metastatic disease and that these single nucleotide polymorphisms (SNPs) could be used to predict outcome in breast cancer patients. To investigate the effect of inherited SNPs on metastasis, we used a mouse genetics approach comparing strains with high (FVB) and low (MOLF) metastatic phenotypes and identified Arntl2, a circadian rhythm transcription factor, as a gene whose differential expression predicted outcome in breast cancer patients. To identify SNP differences in Arntl2 between MOLF and FVB, we performed whole genome sequencing of MOLF and compared it to the FVB genome. Overlapping the data with DNase hypersensitivity sites revealed 10 SNPs in the predicted promoter of Arntl2. To test the causative role of the SNPs on Arntl2 expression in vivo, metastatic cell lines were engineered using the CRISPR-Cas9 approach to specifically replace the FVB Arntl2 promoter with that of MOLF. In agreement with our hypothesis, substitution of the MOLF promoter reduced Arntl2 transcript levels and subsequently decreased lung metastases in orthotopic implantation assays. In vitro pulldown experiments with strain-specific promoter probes revealed potential differential binding of chromatin modifier proteins, demonstrating the significance of the SNPs in regulating Arntl2 transcription. Finally, analysis of SNPs associated with Arntl2 expression in a cohort of Chinese breast cancer patients revealed significant correlation of Arntl2 expression with overall survival, validating this gene as a marker in humans. Since Arntl2 is a transcription factor, current studies are focused on identifying Arntl2-regulated genes to investigate downstream pathways involved in metastasis. This study has important implications regarding the role of circadian rhythm in cancer progression and provides a potential mechanism to explain the increased risk of breast cancers in nightshift workers. Furthermore, this provides the first evidence that transcriptional control elements can be engineered using CRISPR-Cas9 to establish the causative role of SNPs in inherited susceptibility to cancer metastasis.

Citation Format: Ngoc-Han Ha, Kent Hunter. Polymorphisms in the arntl2 promoter affect breast cancer metastasis susceptibility [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3050. doi:10.1158/1538-7445.AM2017-3050

Abstract 2850: A systems genetics approach reveals Rnaseh2c-immune response axis that affects metastasis severity in breast cancer

Metastatic breast cancer is a devastating disease with a 5-year survival rate of only 26%. This is due to a lack of effective therapies against established metastases and an inability to identify high risk patients who would benefit from specific adjuvant therapies to prevent metastatic progression. We have shown in mouse models that spontaneously arising tumors metastasize with different severity based on the mouse genetic background. Using systems genetics approaches we have identified genes correlated with metastasis and survival in both mice and humans. Rnaseh2c was identified as a novel candidate metastasis susceptibility gene. This gene encodes a scaffolding subunit of the Ribonuclease H2 enzyme which removes ribonucleotides misincorporated into the DNA. Experimentally modulating Rnaseh2c expression in a murine mammary cancer cell line resulted in significant changes in pulmonary metastasis, confirming this gene as a metastasis modifier. Mutations in Rnaseh2c are known to cause Aicardi-Goutieres Syndrome, a neurological autoinflammatory disorder that overlaps clinically with congenital viral infections and the autoimmune disease Systemic Lupus Erythematosus. Given this, we hypothesized that altered expression of Rnaseh2c in breast cancer cells affects metastasis by engaging the immune system. To investigate immune system involvement, we analyzed metastasis in immunocompromised mice. T cell deficiency ablated the effect of reduced Rnaseh2c expression on metastasis, revealing for the first time an Rnaseh2c-immune response axis in metastasis. Gene ontology pathway analysis following mRNA-sequencing of Rnaseh2c knockdown and overexpression tumors revealed that 20% of the genes with altered expression are involved in immune system-related pathways, including T cell signaling and antigen presentation. Furthermore, genes with significant changes included Type I interferons, T cell markers, and immune regulators. These results confirm that Rnaseh2c is a novel metastasis modifier gene and validate our hypothesis that the immune system is mediating the effect of Rnaseh2c on metastasis. This mechanism highlights a potential new target for combination with immune modulatory therapies to combat this devastating disease and adds to a panel of genes we identified that together could determine patients with high risk for metastasis.

Citation Format: Sarah Deasy, Kent Hunter. A systems genetics approach reveals Rnaseh2c-immune response axis that affects metastasis severity in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2850. doi:10.1158/1538-7445.AM2017-2850

Errors in interpretation of neck levels in postoperative pathological specimens

Accurate orientation of pathological specimens is of fundamental importance, and specimens that are divided postoperatively may be misinterpreted. We asked surgeons and pathologists to identify boundaries between nodal levels on a clinical photograph of a neck dissection specimen. Few participants were able to identify the boundaries between levels accurately, with several important errors where a marked level contained none of the relevant anatomical tissue. Most errors were in level I, and the number decreased towards level IV. Errors were made by both pathologists and surgeons. The boundaries of level IIA were consistently overestimated, which may have implications for previous studies that evaluated patterns of nodal spread.

Abstract B28: Identification of breast cancer metastasis promoting genes by next generation sequencing

Breast cancer is a leading cause of cancer-related mortality of women in the United States. The majority of cancer deaths are due to metastases rather than the primary tumor, therefore a better understanding of the mechanisms that lead to metastatic disease is critical to reducing breast cancer-related mortality. A majority of cancer cells that leave the primary tumor are either removed by the immune system or fail to survive in distant organs. However, some cancer cells acquire molecular features that allow them to survive and proliferate in secondary sites, such as lung, liver, brain, and bone. In order to design highly efficient anti-metastatic therapies, it is crucial to address metastasis-specific mechanisms of growth and survival. One of the major hurdles to developing these therapies is the genotypic and phenotypic heterogeneity between primary tumors and metastases, as well as between individual metastases. The goal of this project is to characterize the transcriptomic landscape of breast cancer metastases using Next Generation Sequencing (NGS) tools in order to identify potential genes that drive (metastasis promoters) or inhibit (metastasis suppressors) the metastatic outgrowth in distant organs. Therefore, RNA sequencing was performed on breast cancer primary tumors and matching lung metastases from two different mouse models: Polyomavirus Middle-T antigen (PyMT) transgenic mice, a model of spontaneous and highly aggressive breast cancer, as well as from mouse mammary cancer cells orthotopically injected into FVB mice. RNA sequencing using the NGS platform revealed genes that were highly expressed in metastases compared to primary tumors. Interestingly, overlapping the RNA-seq datasets from these two distinct models revealed a shared subset of upregulated genes, strongly suggesting that these genes are likely to be common metastatic outgrowth promoters. To validate these candidate genes, we are currently developing a CRISPR sgRNA library for orthotopic transplant experiments. The genes displaying in vivo effects on metastatic outgrowth in the lungs will be further explored for the development of targeted anti-metastatic therapies.

Citation Format: Karol Szczepanek, Kent Hunter. Identification of breast cancer metastasis promoting genes by next generation sequencing. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr B28.

Abstract B30: Rnaseh2c is a candidate metastasis susceptibility gene in breast cancer

Breast cancer is a leading cause of cancer-related female deaths in the United States, the majority of which are due to distant metastases. Elucidating novel genes that drive metastasis is critical to improving patient outcome. Our laboratory has extensively shown that germline variants impact an individual's susceptibility for metastasis, and we have used this to identify novel metastasis modifier genes. Here we applied a mouse model of spontaneous metastasis to a mouse breeding scheme to screen for strain-specific haplotypes associated with metastatic phenotype. Additional filtering of the haplotype-containing genes was performed for those that were highly expressed in tumors. This screen identified Rnaseh2c, a scaffolding subunit of the Ribonuclease H2 complex which degrades RNA from DNA:RNA heteroduplexes such as those generated during replication and transcription, thus helping maintain genomic stability. Though mutations in RNASEH2C are known to cause the neurological autoinflammatory disorder Aicardi-Goutières Syndrome (AGS), it has not previously been linked to cancer. Given the known pathology of AGS, we hypothesize that differential expression of Rnaseh2c in tumor cells alters tumor progression and metastasis potentially via interaction with the immune system. We directly assessed the effect of tumor cell Rnaseh2c expression on metastasis using in vivo metastasis assays. We implanted into the mammary fat pad tumor cells expressing shRNAs that reduced Rnaseh2c expression and observed significantly fewer pulmonary metastases and reduced tumor burden. To complement this approach, we performed the same metastasis assay with cells overexpressing exogenous Rnaseh2c. In agreement with our initial result, overexpression generated significantly more metastases without affecting primary tumor size, confirming Rnaseh2c as a metastasis modifier. The results thus far validate our approach of employing germline variation in mice to identify novel metastasis modifier genes. Current and future work will focus on elucidating the mechanism by which Rnaseh2c expression impacts metastasis. Specifically, we will determine where Rnaseh2c functions in the metastatic cascade, whether modulated expression disrupts Rnase H2 complex formation, and whether the immune system is involved in mediating this gene's effect on metastasis. Elucidating the mechanism by which this gene acts can contribute to both the development of novel metastasis biomarkers as well as potential therapeutic targets.

Citation Format: Sarah Deasy, Kent Hunter. Rnaseh2c is a candidate metastasis susceptibility gene in breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Metastasis; 2015 Nov 30-Dec 3; Austin, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(7 Suppl):Abstract nr B30.

Hearing in school-aged children with trisomy 21 - results of a longitudinal cohort study in children identified at birth

OBJECTIVES

To report the prevalence of hearing problems and the hearing sequelae in school-aged children with trisomy 21 in a longitudinal study.

DESIGN

All children with trisomy 21 were identified via schools, community-based child development centres, general practitioners, or the universal newborn hearing screen. Audiological data and otorhinolaryngological problems were prospectively entered in to the Audiological Surveillance Programme database from each visit.

SETTING

Retrospective review of the Audiological Surveillance Programme database in the Glasgow area (United Kingdom) of all children reviewed between 2004 and 2012.

PARTICIPANTS

All pre-teenaged children with trisomy 21 of school age (aged 5-12 years old).

MAIN OUTCOME MEASURES

Hearing thresholds, aetiology of hearing loss and management of hearing loss was determined for the cohort of children.

RESULTS

A total of 102 children were included. Fifty-four had normal hearing. Twenty-six had fluctuating otitis media with effusion; five had hearing in normal limits, six were managed with hearing aids, fourteen were managed conservatively, and one had ventilation tube insertion. Fifteen had persistent otitis media with effusion; four had ventilation tube insertion; and nine were managed with hearing aids. Seven had mixed hearing loss with four required hearing aids.

CONCLUSIONS

Otitis media with effusion was the commonest cause of hearing impairment; effusions may fluctuate through the pre-teenaged years, and thus, hearing aids are beneficial. Ventilation tube insertion and bone-conducting hearing aids were useful when ear-level hearing aids were not tolerated. Mixed hearing loss occurred in later years as sensorineural hearing loss developed on a background of otitis media with effusion.

CCL9 Induced by TGFβ Signaling in Myeloid Cells Enhances Tumor Cell Survival in the Premetastatic Organ

Tumor cell survival in the hostile distant organ is a rate-limiting step in cancer metastasis. Bone marrow-derived myeloid cells can form a premetastatic niche and provide a tumor-promoting microenvironment. However, it is unclear whether these myeloid cells in the premetastatic site have any direct effect on tumor cell survival. Here, we report that chemokine CCL9 was highly induced in Gr-1(+)CD11b(+) immature myeloid cells and in premetastatic lung in tumor-bearing mice. Knockdown of CCL9 in myeloid cells decreased tumor cell survival and metastasis. Importantly, CCL9 overexpression in myeloid cells lacking TGFβ signaling rescued the tumor metastasis defect observed in mice with myeloid-specific Tgfbr2 deletion. The expression level of CCL23, the human orthologue for CCL9, in peripheral blood mononuclear cells correlated with progression and survival of cancer patients. Our study demonstrates that CCL9 could serve as a good candidate for anti-metastasis treatment by targeting the rate-limiting step of cancer cell survival. In addition, targeting CCL9 may avoid the adverse effects of TGFβ-targeted therapy.

Abstract 3172: CCL9 induction in myeloid cells of the premetastatic niche enhances tumor cell survival and metastatic colonization

Tumor cell survival in the hostile distant organ is a rate-limiting step in cancer metastasis. Bone marrow-derived myeloid cells can form a premetastatic niche and provide a tumor-promoting microenvironment. However, it is unclear whether these myeloid cells in the premetastatic site have any direct effect on tumor cell survival. Here we report that chemokine CCL9 was highly induced in Gr-1+CD11b+ immature myeloid cells and in premetastatic lung of mice bearing 4T1 mammary tumor and B16 melanoma. Knockdown of CCL9 in myeloid cells decreased tumor cell survival and metastasis. The expression level of CCL23, the human orthologue for CCL9, in peripheral blood mononuclear cells correlated with progression and survival of cancer patients. Our studies identify CCL9 as a key pro-survival factor for cancer cells in the premetastatic organ.

Interestingly, the expression of CCL9 in myeloid cells is regulated by TGF-β signaling as overexpression of CCL9 in myeloid cells lacking TGF-β signaling rescued the tumor metastasis defect observed in mice with myeloid-specific deletion of TGF-β signaling. These data together with our previous report of a fundamental role of myeloid TGF-β signaling in host compromised immune surveillance (Cancer Discovery 2013); demonstrate that myeloid-specific TGF-β signaling constitutes an essential component of the metastasis-promoting puzzle of TGF-β. This finding is different from TGF-β signaling in fibroblasts and a variety of epithelial cells, as well as T cells in which the TGF-β signaling functions as a tumor suppressor. This new understanding of TGF-β at the interface of tumor and host may provide insight into how TGF-β switches from a tumor suppressor to a tumor promoter, a long-standing challenge in cancer biology field. Our study demonstrates that CCL9 could serve as a good candidate for anti-metastasis treatment by targeting the rate-limiting step of cancer cell survival. Additionally, targeting CCL9 may avoid the adverse effects of TGF-β-targeted therapy.

Citation Format: Hannah HY Yan, Yanli Pang, Kent Hunter, Chand Khanna, Li Yang. CCL9 induction in myeloid cells of the premetastatic niche enhances tumor cell survival and metastatic colonization. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3172. doi:10.1158/1538-7445.AM2015-3172

The role of individual inheritance in tumor progression and metastasis

Metastasis, the dissemination and growth of tumor cells at secondary sites, is the primary cause of patient mortality from solid tumors. Metastasis is an extremely complex, inefficient process requiring contributions of not only the tumor cell but also local and distant environmental factors, at both the cellular and molecular level. Variation in the function of any of the steps in the metastatic cascade may therefore have profound implications for the ultimate course of the disease. In addition to the somatic and cellular heterogeneity that can affect cancer outcome, an individual's specific ancestry or genetic background can also significantly influence metastatic progression. These inherited variants not only encoded for metastatic susceptibility but also provided a window to study critical factors that are not easily accessible with current technologies. Furthermore, investigations into inherited metastatic susceptibility enable identification of important molecular and cellular processes that are not subject to mutation and are consequently not detectable by standard cancer genome sequencing strategies. Incorporation of inherited variation into metastasis research therefore provides methods to more comprehensively investigate the etiology of the lethal consequences of tumor progression.

Investigating the effects of an oral fructose challenge on hepatic ATP reserves in healthy volunteers: A (31)P MRS study

BACKGROUND

Impaired homeostasis of hepatic ATP has been associated with NAFLD. An intravenous fructose infusion has been shown to be an effective challenge to monitor the depletion and subsequent recovery of hepatic ATP reserves using (31)P MRS.

AIMS

The purpose of this study was to evaluate the effects of an oral rather than intravenous fructose challenge on hepatic ATP reserves in healthy subjects.

METHODS

Self-reported healthy males were recruited. Following an overnight fast, baseline liver glycogen and lipid levels were measured using Magnetic Resonance Spectroscopy (MRS). Immediately after consuming a 500 ml 75 g fructose drink (1275 kJ) subjects were scanned continuously for 90 min to acquire dynamic (31)P MRS measurements of liver ATP reserves.

RESULTS

A significant effect on ATP reserves was observed across the time course (P < 0.05). Mean ATP levels reached a minimum at 50 min which was markedly lower than baseline (80 ± 17% baseline, P < 0.05). Subsequently, mean values tended to rise but did not reach statistical significance above minimum. The time to minimum ATP levels across subjects was negatively correlated with BMI (R(2) = 0.74, P < 0.005). Rates of ATP recovery were not significantly correlated with BMI or liver fat levels, but were negatively correlated with baseline glycogen levels (R(2) = 0.7, P < 0.05).

CONCLUSIONS

Depletion of ATP reserves can be measured non-invasively following an oral fructose challenge using (31)P MRS. BMI is the best predictor of postprandial ATP homeostasis following fructose consumption.

A multi-megabase copy number gain causes maternal transmission ratio distortion on mouse chromosome 2

Significant departures from expected Mendelian inheritance ratios (transmission ratio distortion, TRD) are frequently observed in both experimental crosses and natural populations. TRD on mouse Chromosome (Chr) 2 has been reported in multiple experimental crosses, including the Collaborative Cross (CC). Among the eight CC founder inbred strains, we found that Chr 2 TRD was exclusive to females that were heterozygous for the WSB/EiJ allele within a 9.3 Mb region (Chr 2 76.9 - 86.2 Mb). A copy number gain of a 127 kb-long DNA segment (designated as responder to drive, R2d) emerged as the strongest candidate for the causative allele. We mapped R2d sequences to two loci within the candidate interval. R2d1 is located near the proximal boundary, and contains a single copy of R2d in all strains tested. R2d2 maps to a 900 kb interval, and the number of R2d copies varies from zero in classical strains (including the mouse reference genome) to more than 30 in wild-derived strains. Using real-time PCR assays for the copy number, we identified a mutation (R2d2WSBdel1) that eliminates the majority of the R2d2WSB copies without apparent alterations of the surrounding WSB/EiJ haplotype. In a three-generation pedigree segregating for R2d2WSBdel1, the mutation is transmitted to the progeny and Mendelian segregation is restored in females heterozygous for R2d2WSBdel1, thus providing direct evidence that the copy number gain is causal for maternal TRD. We found that transmission ratios in R2d2WSB heterozygous females vary between Mendelian segregation and complete distortion depending on the genetic background, and that TRD is under genetic control of unlinked distorter loci. Although the R2d2WSB transmission ratio was inversely correlated with average litter size, several independent lines of evidence support the contention that female meiotic drive is the cause of the distortion. We discuss the implications and potential applications of this novel meiotic drive system.

Serum levels of the progesterone induced blocking factor do not precipitously rise in women with gynecologic cancer in contrast to women exposed to progesterone

PURPOSE

To determine if an immunomodulatory protein (progesterone induced blocking factor [PIBF]) that is progesterone induced and found in higher concentration during pregnancy is similarly found with increased levels in women with gynecologic cancers.

MATERIALS AND METHODS

A newly developed enzyme linked immunoabsorbent assay (ELISA) assay was used to measure PIBF in the sera of six women with various gynecologic cancers and compare them to five controls (three with benign tumors and two having gynecologic procedures for non-tumors.

RESULTS

The PIBF levels in women with gynecologic cancer did not rise precipitously as historical controls of women or men exposed to progesterone. The two highest PIBF levels of the 11 subjects were in women with gynecologic cancer.

CONCLUSIONS

The data suggest that if PIBF helps cancer cells to evade immune surveillance, it probably operates through an intracytoplasmic presence. If an increase in sera PIBF could have been detected in women with gynecologic cancer, then this ELISA test could have been used to detect tumor recurrence. Future studies may concentrate on evaluating intracytoplasmic PIBF to possibly help determine which tumors may respond to progesterone antagonist receptors.

Understanding susceptibility to breast cancer metastasis: the genetic approach

Metastasis is a complex phenotype that is not discrete, is polygenic, varies in range over the entire population and follows non-Mendelian inheritance. Recent evidence indicates that inherited susceptibility affects not only the development of the primary tumor, but is also an important factor in progression and metastasis. Since metastasis accounts for the majority of breast cancer deaths, identification and understanding of the genetic modifiers of metastasis underlies success of personalized therapy. Studies from our laboratory and others have now characterized several metastasis susceptibility factors. While an important step forward, these certainly do not describe the entire metastatic phenomenon and efforts continue to expand this knowledge. Here we review the complex metastatic process and current knowledge on the genetics of breast cancer metastasis, including germline polymorphisms that have been associated with the disease.