Astrocytes promote progression of breast cancer metastases to the brain via a KISS1-mediated autophagy

Formation of metastases, also known as cancer dissemination, is an important stage of breast cancer (BrCa) development. KISS1 expression is associated with inhibition of metastases development. Recently we have demonstrated that BrCa metastases to the brain exhibit low levels of KISS1 expression at both mRNA and protein levels. By using multicolor immunofluorescence and coculture techniques here we show that normal adult astrocytes in the brain are capable of promoting metastatic transformation of circulating breast cancer cells localized to the brain through secretion of chemokine CXCL12. The latter was found in this study to downregulate KISS1 expression at the post-transcriptional level via induction of microRNA-345 (MIR345). Furthermore, we demonstrated that ectopic expression of KISS1 downregulates ATG5 and ATG7, 2 key modulators of autophagy, and works concurrently with autophagy inhibitors, thereby implicating autophagy in the mechanism of KISS1-mediated BrCa metastatic transformation. We also found that expression of KISS1 in human breast tumor specimens inversely correlates with that of MMP9 and IL8, implicated in the mechanism of metastatic invasion, thereby supporting the role of KISS1 as a potential regulator of BrCa metastatic invasion in the brain. This conclusion is further supported by the ability of KISS1, ectopically overexpressed from an adenoviral vector in MDA-MB-231Br cells with silenced expression of the endogenous gene, to revert invasive phenotype of those cells. Taken together, our results strongly suggest that human adult astrocytes can promote brain invasion of the brain-localized circulating breast cancer cells by upregulating autophagy signaling pathways via the CXCL12-MIR345- KISS1 axis.

Abstract 1145: Overcoming chemoresistance and blocking metastasis in breast cancer by targeting HuR

Patients with metastatic breast cancer have a dismal 5-year survival rate of only 24%. Chemoresistance is another contributor to the high mortality of advanced breast cancer. The RNA-binding protein, Hu antigen R (HuR), is overexpressed at all stages of breast cancer development. Cytoplasmic HuR accumulation correlates with high-grade malignancy, poor distant disease-free survival and serves as a prognostic factor for poor clinical outcome in breast cancer. HuR promotes tumorigenesis by promoting mRNA stability and translation of proteins implicated in proliferation, survival, angiogenesis, invasion, and metastasis. HuR also modulates sensitivity of breast cancer cells to chemotherapy. Taken together, HuR is an emerging target for breast cancer therapy, especially metastatic breast cancer. Using shRNA and CRISPR technologies to modulate HuR expression in breast cancer cells, we found that cells with HuR KD/KO were less invasive and more sensitive to chemotherapy. In an effort to discover small molecules that disrupt the HuR-mRNA interaction and block HuR functions in breast cancer progression, metastasis and chemoresistance, high throughput screening (HTS) was carried out in several chemical libraries (~23,000 compounds) using fluorescence polarization (FP) assay, which identified several initial hits with sub-micromolar inhibitory constants (Ki). Those potential inhbitors were then validated by ALPHA assay (Amplified Luminescent Proximity Homogeneous Assay), confirmed by Surface Plasmon Resonance (SPR). In cell-based assays, top hit KH-3 and its optimized analogs, specifically shortened HuR target mRNA half-lifes and decreased the level of the encoded proteins. Moreover, those compounds inhibited invasion and restored chemosensitivity. qPCR arrays focusing on specific pathways revealed that HuR inhibitors potently upregulated metastatic suppressors and downregulated genes frequently overexpressed in lung metastases. In animal studies, KH-3 not only exhibited potent antitumor efficacy in orthotopic xenografts of breast cancer, but also efficiently blocked experimental metastasis. In conclusion, we identified potent and specific small molecule inhibitors of HuR-mRNA interaction for potential anti-metastatic therapy for breast cancer with HuR overexpression.

Citation Format: Xiaoqing Wu, Rebecca Marquez, Shuang Han, Lan Lan, Dan A. Dixon, Jeffrey Aubé, Danny R. Welch, Liang Xu. Overcoming chemoresistance and blocking metastasis in breast cancer by targeting HuR [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 1145. doi:10.1158/1538-7445.AM2017-1145

Abstract 4841: Suppression of metastasis by KP54 and non-KP54 kisspeptins

KISS1 is a secreted neuropeptide which can act as a metastasis suppressor protein. Expression of KISS1 inhibits metastatic colonization at secondary sites, rendering disseminated cells dormant. In order for KISS1 to suppress metastasis, it must be secreted outside of the cell, where furin cleaves KISS1 into kisspeptins. This cleavage liberates an internal kisspeptin, Kisspeptin-54 (KP54, K67 to F121), which is amidated and has the ability to bind a Gq/11-coupled protein receptor KISS1R. The mechanism of action for KISS1 metastasis suppression has long been assumed to be KP54 interacting with KISS1R. However, expression of KISS1R is not necessary for KISS1 metastasis suppression, and the extracellular processing of KISS1 hints at an alternative hypothesis: a different kisspeptin may be responsible for suppressing metastasis. To test this hypothesis, all possible kisspeptins were generated based on known dibasic cleavage sites (M1-Q145; M1-R56; M1-R67; M1-R124; R56-R66; R67-F121; R56-F121; R56-Q145; R67-Q145; R124-Q145) and were cloned to include the same secretion sequence as nascent KISS1. These kisspeptins (KISS1 Manufactured Peptides, or KMP) were independently expressed in B16-F10 murine melanoma cells. To test for experimental metastasis, B16-F10 cells expressing KMP were injected intravenously into the lateral tail vein of syngeneic mice and the lungs were examined for metastatic load. While KP54 suppressed metastasis, additional KMP lacking the KISS1R binding site (LRF-NH2) were able to completely suppress metastasis (p<0.05). When assessing metastasis-associated traits in vitro, suppressor KMP suppressed motility, increased mitochondrial biomass, and increased oxidative phosphorylation (phenotypes previously reported with KISS1 expression). In particular, one kisspeptin (KMP2, M1 - R56) suppressed metastatic traits in vitro as well as completely suppressing metastasis in vivo. As a whole, these data suggest that metastasis suppression by KISS1 is not necessarily contingent on KISS1R activation, and also supports investigation into additional receptors.

Citation Format: Kelsey Rebecca Hampton, Keke M. Pounds, Andrew P. Trembath, Danny R. Welch. Suppression of metastasis by KP54 and non-KP54 kisspeptins [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 4841. doi:10.1158/1538-7445.AM2017-4841

Abstract 2836: Mitochondrial genomic backgrounds differentially affect nuclear DNA methylation and gene expression

Accumulating data implicate mitochondrial genetics and metabolism as contributors to metastatic efficiency. With only 13 proteins encoded by the mtDNA genome, the mechanism(s) by which the coordination of multiple genes involved in metastasis could occur is unclear. We hypothesized that mitochondrial DNA (mtDNA) polymorphisms would differentially regulate nuclear DNA (nDNA) methylation and gene expression. To test the hypotheses, we created Mitochondrial Nuclear Exchange (MNX) mice, by transferring an oocyte nucleus from strainx into an enucleated oocyte from strainy. The mice show that mammary tumor formation and metastasis are regulated by inherited mitochondrial polymorphisms (PMID: 26471915). Age-matched, male mouse brains were collected and pooled from four litter mates representing each of the wild-type and MNX mice (8 groups). Genome-wide nDNA methylation (Mouse methyl-Seq) and gene expression (RNA-Seq) were measured and results validated in independent replicate samples. Significant, selective and reproducible differential DNA methylation and gene expression were observed and validated between strains having identical nDNA, but different mtDNA. While the signal(s) from mitochondria altering methylation is not fully defined, the findings support the hypothesis and demonstrate how mitochondrial genetic alterations could be one of several quantitative trait loci involved in complex phenotypes, such as metastasis. The results also suggest that mtDNA polymorphisms could serve as predictive biomarkers for cancer aggressiveness. Support: Susan G. Komen for the Cure (SAC11037), Natl Fndn Cancer Res, Biomedical Research Training Program, Kansas Bioscience Authority, CA134981, P30-CA168524.

Citation Format: Carolyn J. Vivian, Amanda E. Brinker, Stefan Graw, Devin C. Koestler, Christophe Legendre, Gerald C. Gooden, Bodour Salhia, Danny R. Welch. Mitochondrial genomic backgrounds differentially affect nuclear DNA methylation and gene expression [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 2836. doi:10.1158/1538-7445.AM2017-2836

Mitochondrial Genomic Backgrounds Affect Nuclear DNA Methylation and Gene Expression

Mitochondrial DNA (mtDNA) mutations and polymorphisms contribute to many complex diseases, including cancer. Using a unique mouse model that contains nDNA from one mouse strain and homoplasmic mitochondrial haplotypes from different mouse strain(s)-designated Mitochondrial Nuclear Exchange (MNX)-we showed that mtDNA could alter mammary tumor metastasis. Because retrograde and anterograde communication exists between the nuclear and mitochondrial genomes, we hypothesized that there are differential mtDNA-driven changes in nuclear (n)DNA expression and DNA methylation. Genome-wide nDNA methylation and gene expression were measured in harvested brain tissue from paired wild-type and MNX mice. Selective differential DNA methylation and gene expression were observed between strains having identical nDNA, but different mtDNA. These observations provide insights into how mtDNA could be altering epigenetic regulation and thereby contribute to the pathogenesis of metastasis. Cancer Res; 77(22); 6202-14. ©2017 AACR.

Gd2O3-doped silica @ Au nanoparticles for in vitro imaging cancer biomarkers using surface-enhanced Raman scattering

There has been an interest in developing multimodal approaches to combine the advantages of individual imaging modalities, as well as to compensate for respective weaknesses. We previously reported a composite nano-system composed of gadolinium-doped mesoporous silica nanoparticle and gold nanoparticle (Gd-Au NPs) as an efficient MRI contrast agent for in vivo cancer imaging. However, MRI lacks sensitivity and is unsuitable for in vitro cancer detection. Thus, here we performed a study to use the Gd-Au NPs for detection and imaging of a widely recognized human cancer biomarker, epidermal growth factor receptor (EGFR), in individual human cancer cells with surface-enhanced Raman scattering (SERS). The Gd-Au NPs were sequentially conjugated with a monoclonal antibody recognizing EGFR and a Raman reporter molecule, 4-meraptobenzoic acid (MBA), to generate a characteristic SERS signal at 1075cm^-1. By spatially mapping the SERS intensity at 1075cm^-1, cellular distribution of EGFR and its relocalization on the plasma membrane were measured in situ. In addition, the EGFR expression levels in three human cancer cell lines (S18, A431 and A549) were measured using this SERS probe, which were consistent with the comparable measurements using immunoblotting and immunofluorescence. Our SERS results show that functionalized Gd-Au NPs successfully targeted EGFR molecules in three human cancer cell lines and monitored changes in single cell EGFR distribution in situ, demonstrating its potential to study cell activity under physiological conditions. This SERS study, combined with our previous MRI study, suggests the Gd-Au nanocomposite is a promising candidate contrast agent for multimodal cancer imaging.

The KISS1 metastasis suppressor appears to reverse the Warburg effect by shifting from glycolysis to mitochondrial beta-oxidation

The shift by cancer cells toward aerobic glycolysis (Warburg effect) confers selective advantages by utilizing nutrients (e.g., lipids, amino acids, and nucleotides) to build biomass. Lipogenesis is generally enhanced, and its inhibition diminishes proliferation and survival. Re-expression of the metastasis suppressor KISS1 in human melanoma cells results in greater mitochondrial biogenesis, inhibition of glycolysis, utilization of beta-oxidation to provide energy, elevated oxidation of exogenous fatty acids, and increased expression of early-phase lipogenesis genes at both mRNA and protein levels. Correspondingly, the energy sensor AMPKβ is phosphorylated, resulting in inhibitory phosphorylation of acetyl-CoA carboxylase (ACC), which is linked to enhanced beta-oxidation. Furthermore, PGC1α is required for KISS1-mediated phosphorylation of ACC and metastasis suppression. Collectively, these data further support the linkages between macromolecular metabolism and metastasis.

KEY MESSAGES

• KISS1 alters fatty acid metabolism. • There may be connections between metastasis and metabolism. • PGC1alpha appears to be downstream mediator of KISS1 metastasis suppression.

Suppression of pancreatic cancer growth and metastasis by HMP19 identified through genome-wide shRNA screen

Therapeutic effectiveness against metastatic or even locally advanced pancreatic ductal adenocarcinoma (PDAC) is dismal, with 5‐year survival less than 5%. Even in patients who undergo potentially curative resection, most patients' tumors recur in the liver. Improving therapies targeting or preventing liver metastases is crucial for improving prognosis. To identify genes suppressing metastasis, a genome‐wide shRNA screen was done using the human non‐metastatic PDAC cell line, S2‐028. After identification of candidates, functional validation was done using intrasplenic and orthotopic injections in athymic mice. HMP19 strongly inhibited metastasis but also partially attenuated tumor growth in the pancreas. Knockdown of HMP19 increased localization of activated ERK1/2 in the nucleus, corresponding to facilitated cell proliferation, decreased p27^Kip1 and increased cyclin E1. Over‐expression of HMP19 exerted the opposite effects. Using a tissue microarray of 84 human PDAC, patients with low expression of HMP19 showed significantly higher incidence of liver metastasis (p = 0.0175) and worse prognosis (p = 0.018) after surgery. HMP19, a new metastasis/tumor suppressor in PDAC, appears to alter signaling that leads to cell proliferation and appears to offer prognostic value in human PDAC.

What's new?

Pancreatic cancer is a frequently intractable disease, due in part to its late diagnosis and propensity to metastasize. Indeed, potentially curative resection fails in more than half of patients with pancreatic ductal adenocarcinoma (PDAC), owing to recurrence in the pancreas as well as to metastasis, particularly to the liver. Prognosis may be improved, however, by leveraging the inhibitory strength of novel metastasis suppressors. A promising candidate is HMP19, described in this study. In xenograft models, HMP19 overexpression significantly suppressed PDAC tumor growth and spread. Its elevated expression in clinical samples was associated with reduced liver metastasis and improved patient survival.

Tumor Cell Invasion-Not All Barriers Are Created Equal

The importance of invasion in the complex process of metastasis, although now well established, has been studied with increasing molecular detail due to the development of robust in vitro experimental assays. In this issue of Cancer Research, we highlight a paper published by George Poste and colleagues that compared and contrasted several different invasion assays. The authors concluded that various barriers impose different selective pressures and that simply enriching for invasive ability did not necessarily translate into greater metastasis efficiency. Although perhaps obvious now, these findings were surprising when they were published. Certainly, the data highlight the importance of tumor cell-microenvironment interactions and the necessity to interpret experiments taking the context into consideration. Cancer Res; 76(7); 1675-6. ©2016 AACRSee related article by Poste et al., Cancer Res 1980;40:1636-44.

Cyclin-dependent kinase-mediated phosphorylation of breast cancer metastasis suppressor 1 (BRMS1) affects cell migration

Expression of Breast Cancer Metastasis Suppressor 1 (BRMS1) reduces the incidence of metastasis in many human cancers, without affecting tumorigenesis. BRMS1 carries out this function through several mechanisms, including regulation of gene expression by binding to the mSin3/histone deacetylase (HDAC) transcriptional repressor complex. In the present study, we show that BRMS1 is a novel substrate of Cyclin-Dependent Kinase 2 (CDK2) that is phosphorylated on serine 237 (S237). Although CDKs are known to regulate cell cycle progression, the mutation of BRMS1 on serine 237 did not affect cell cycle progression and proliferation of MDA-MB-231 breast cancer cells; however, their migration was affected. Phosphorylation of BRMS1 does not affect its association with the mSin3/HDAC transcriptional repressor complex or its transcriptional repressor activity. The serine 237 phosphorylation site is immediately proximal to a C-terminal nuclear localization sequence that plays an important role in BRMS1-mediated metastasis suppression but phosphorylation does not control BRMS1 subcellular localization. Our studies demonstrate that CDK-mediated phosphorylation of BRMS1 regulates the migration of tumor cells.

Crocetinic acid inhibits hedgehog signaling to inhibit pancreatic cancer stem cells

Pancreatic cancer is the fourth leading cause of cancer deaths in the US and no significant treatment is currently available. Here, we describe the effect of crocetinic acid, which we purified from commercial saffron compound crocetin using high performance liquid chromatography. Crocetinic acid inhibits proliferation of pancreatic cancer cell lines in a dose- and time-dependent manner. In addition, it induced apoptosis. Moreover, the compound significantly inhibited epidermal growth factor receptor and Akt phosphorylation. Furthermore, crocetinic acid decreased the number and size of the pancospheres in a dose-dependent manner, and suppressed the expression of the marker protein DCLK-1 (Doublecortin Calcium/Calmodulin-Dependent Kinase-1) suggesting that crocetinic acid targets cancer stem cells (CSC). To understand the mechanism of CSC inhibition, the signaling pathways affected by purified crocetinic acid were dissected. Sonic hedgehog (Shh) upon binding to its cognate receptor patched, allows smoothened to accumulate and activate Gli transcription factor. Crocetinic acid inhibited the expression of both Shh and smoothened. Finally, these data were confirmed in vivo where the compound at a dose of 0.5 mg/Kg bw suppressed growth of tumor xenografts. Collectively, these data suggest that purified crocetinic acid inhibits pancreatic CSC, thereby inhibiting pancreatic tumorigenesis.

Abstract 1615: Metastasis suppression by KP54 and non-KP54 kisspeptins

The KISS1 metastasis suppressor blocks metastasis by inhibiting colonization at secondary sites. In order to suppress metastasis, KISS1 must be secreted and cleaved by furin into kisspeptins. Kisspeptin-54 (KP54, K67 to F121) binds a G-protein coupled receptor, KISS1R, and the mechanism of metastasis suppression has been assumed to be through KP54 binding with KISS1R. However, since KISS1 is cleaved extracellularly, and since none of the cells tested express KISS1R, an alternate hypothesis is required - another kisspeptin is responsible for suppressing metastasis. To test this hypothesis, we engineered all ten of the possible kisspeptins based upon predicted dibasic cleavage sites (M1-Q145; M1-R56; M1-R67; M1-R124; R56-R66; R67-F121; R56-F121; R56-Q145; R67-Q145; R124-Q145). The (KISS1 Manufactured Peptides, or KMP) each contained the same secretion signal as nascent KISS1 and were designated KMP1 to KMP10 respectively. Each KMP was expressed individually in B16-F10 melanoma cells. Following intravenous injection, experimental lung metastases were quantified. While KP54 expression suppressed metastasis, other KMP lacking the KISS1R binding motif also suppressed metastasis as or more effectively (p<0.05). In vitro, cell lines expressing suppressor KMP inhibited motility, increased mitochondrial biomass, and elevated levels of oxidative phosphorylation (phenotypes previously correlated with KISS1 function). In particular, KMP2 (M1 - R56) completely suppressed metastasis. Collectively, these data demonstrate that the mechanism of action for metastasis suppression by KISS1 does not necessarily require activation of KISS1R, and also suggests the existence of additional receptors.

Support: CA134981, Natl Fndn Cancer Res, Komen SAC11037, KS Bioscience Auth, P30-CA168524, Steiner Family Fund for Metastasis Research.

Citation Format: Kelsey R. Hampton, Keke M. Pounds, Andrew P. Trembath, Danny R. Welch. Metastasis suppression by KP54 and non-KP54 kisspeptins. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1615.

Abstract 4832: Overcoming breast cancer chemoresistance and blocking metastasis by targeting RNA-binding protein HuR

Patients with metastatic breast cancer have a dismal 5-year survival rate of only 24%. Chemoresistance is another contributor to the high mortality of advanced breast cancer. The RNA-binding protein, Hu antigen R (HuR), is overexpressed at all stages of breast cancer development. Cytoplasmic HuR accumulation correlates with high-grade malignancy, poor distant disease-free survival and serves as a prognostic factor for poor clinical outcome in breast cancer. HuR promotes tumorigenesis by promoting mRNA stability and translation of proteins implicated in proliferation, survival, angiogenesis, invasion, and metastasis. HuR also modulates sensitivity of breast cancer cells to chemotherapy. Taken together, HuR is an emerging target for breast cancer therapy, especially metastatic breast cancer. Using shRNA and CRISPR technologies to modulate HuR expression in breast cancer cells, we found that cells with HuR KD/KO were less invasive and more sensitive to chemotherapy. In an effort to discover small molecules that disrupt the HuR-mRNA interaction and block HuR functions in breast cancer progression, metastasis and chemoresistance, high throughput screening (HTS) was carried out using several chemical libraries (∼23,000 compounds) using fluorescence polarization (FP) assay and identified several initial hits with sub-micromolar inhibitory constants (Ki). Those potential disruptors were then validated by ALPHA assay (Amplified Luminescent Proximity Homogeneous Assay), confirmed by Surface Plasmon Resonance (SPR). In cell-based assays, top hit KH-3 and its optimized analogs, specifically shortened HuR target mRNA half-lifes and decreased the level of the encoded proteins. Moreover, those compounds inhibited invasion and restored chemosensitivity. qPCR arrays focusing on specific pathways revealed that HuR inhibitors potently upregulated metastatic suppressors and downregulated genes frequently overexpressed in lung metastases. In animal studies, KH-3 not only powerfully exhibited antitumor efficacy in orthotopic xenografts, but also efficiently blocked experimental metastasis. In conclusion, we identified potent and specific small molecule disrupters of HuR-mRNA interaction for potential anti-metastatic therapy for breast cancer with HuR overexpression.

Citation Format: Xiaoqing Wu, Rebecca T. Marquez, Shuang Han, Ke Li, Lan Lan, Yuxiao Guo, Dan A. Dixon, Jeffrey Aubé, Danny R. Welch, Liang Xu. Overcoming breast cancer chemoresistance and blocking metastasis by targeting RNA-binding protein HuR. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4832.

Abstract 1696: Mitochondrial haplotype alters metastasis in a non-cell autonomous manner

Mitochondrial Nuclear Exchange (MNX) mice, created by transferring the nucleus from an oocyte from strain x into an enucleated oocyte of strain y, showed that mammary tumor formation and metastasis can be regulated by inherited mitochondrial polymorphisms (PMID26471915). Besides genetic (cell autonomous) changes observed, we asked whether mitochondrial polymorphisms in non-cancer compartments could exert effects on tumor formation or metastasis. Tumor cells were injected into syngeneic wild type mice and tumor growth and metastasis were compared to similarly injected cells into MNX mice sharing the same nuclear but different mtDNA backgrounds. Orthotopic tumor growth rates were equal for all of the cell lines tested. However, the ability to form experimental lung metastases following i.v. injection were dramatically altered. Compared to injections into wild-type, syngeneic mice, E0771 mammary carcinoma and B16-F10 melanoma cells (both syngeneic to C57BL/6J), formed significantly (P<0.01) more lung metastases in C57BL/6J-mtMNX(C3H/HeN) and K1735-M2 melanoma cells (syngeneic to C3H/HeN) formed significantly fewer lung metastases in C3H/HeNmtMNXC57BL/6J. These results have been replicated at least three times using >10 mice per experiment. Interestingly, C57BL/6J mitochondria confer resistance to metastasis in both cell autonomous and non-cell autonomous experiments. Basal metabolic differences comparing mouse embryonic fibroblasts isolated from wild-type and MNX mice are among mechanisms being explored. Together, our findings highlight the striking influences that mitochondrial haplotypes can exert on tumorigenicity and metastasis via both intrinsic and extrinsic mechanisms. Support: Susan G. Komen for the Cure (SAC11037), Natl Fndn Cancer Res, Steiner Family Fund for Metastasis Research, Kansas Bioscience Authority, CA134981, P30-CA168524

Citation Format: Amanda E. Brinker, Carolyn J. Vivian, Danny R. Welch. Mitochondrial haplotype alters metastasis in a non-cell autonomous manner. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1696.

Mitochondrial Genetics Regulate Breast Cancer Tumorigenicity and Metastatic Potential

Current paradigms of carcinogenic risk suggest that genetic, hormonal, and environmental factors influence an individual's predilection for developing metastatic breast cancer. Investigations of tumor latency and metastasis in mice have illustrated differences between inbred strains, but the possibility that mitochondrial genetic inheritance may contribute to such differences in vivo has not been directly tested. In this study, we tested this hypothesis in mitochondrial-nuclear exchange mice we generated, where cohorts shared identical nuclear backgrounds but different mtDNA genomes on the background of the PyMT transgenic mouse model of spontaneous mammary carcinoma. In this setting, we found that primary tumor latency and metastasis segregated with mtDNA, suggesting that mtDNA influences disease progression to a far greater extent than previously appreciated. Our findings prompt further investigation into metabolic differences controlled by mitochondrial process as a basis for understanding tumor development and metastasis in individual subjects. Importantly, differences in mitochondrial DNA are sufficient to fundamentally alter disease course in the PyMT mouse mammary tumor model, suggesting that functional metabolic differences direct early tumor growth and metastatic efficiency.

Tumor Heterogeneity--A 'Contemporary Concept' Founded on Historical Insights and Predictions

Heterogeneity is commonplace in all cancer types and at several levels--intrinsic (genetic), epigenetic, positional, and at the population level. The different subpopulations with a tumor mass communicate with each other and influence the behavior of other tumor cells both locally and at a distance. These properties have profound implications regarding the understanding of tumor behavior and how therapies are (or should be) administered. This brief commentary highlights the insightful review of Gloria Heppner and how it has influenced cancer research even three decades after it was published.

Generation of Mitochondrial-nuclear eXchange Mice via Pronuclear Transfer

The mitochondrial paradigm for common disease proposes that mitochondrial DNA (mtDNA) sequence variation can contribute to disease susceptibility and progression. To test this concept, we developed the Mitochondrial-nuclear eXchange (MNX) model, in which isolated embryonic pronuclei from one strain of species are implanted into an enucleated embryo of a different strain of the same species (e.g., C57BL/6 and C3H/HeN, Mus musculus), generating a re-constructed zygote harboring nuclear and mitochondrial genomes from different strains. Two-cell embryos are transferred to the ostia of oviducts in CD-1 pseudopregnant mice and developed to term. Nuclear genotype and mtDNA haplotype are verified in offspring, and females selected as founders for desired MNX colonies. By utilizing MNX models, many new avenues for the in vivo study for mitochondrial and nuclear genetics, or mito-Mendelian genetics, are now possible.

In vitro biophysical, microspectroscopic and cytotoxic evaluation of metastatic and non-metastatic cancer cells in responses to anti-cancer drug

The Breast Cancer Metastasis Suppressor 1 (BRMS1) is a nucleo-cytoplasmic protein that suppresses cancer metastasis without affecting the growth of the primary tumor. Previous work has shown that it decreases the expression of protein mediators involved in chemoresistance. This study measured the biomechanical and biochemical changes in BRMS1 expression and the responses of BRMS1 to drug treatments on cancer cells in vitro. The results show that BRMS1 expression affects biomechanical properties by decreasing the Young's modulus and adhesion force of breast cancer cells after doxorubicin (DOX) exposure. Raman spectral bands corresponding to DNA/RNA, lipids and proteins were similar for all cells after DOX treatment. The expression of cytokines were similar for cancer cells after DOX exposure, although BRMS1 expression had different effects on the secretion of cytokines for breast cancer cells. The absence of significant changes on apoptosis, reactive oxygen species (ROS) expression and cell viability after BRMS1 expression shows that BRMS1 has little effect on cellular chemoresistance. Analyzing cancer protein expression is critical in evaluating therapeutics. Our study may provide evidence of the benefit of metastatic suppressor expression before chemotherapy.

Essential Components of Cancer Education

Modern cancer therapy/care involves the integration of basic, clinical, and population-based research professionals using state-of-the-art science to achieve the best possible patient outcomes. A well-integrated team of basic, clinical, and population science professionals and educators working with a fully engaged group of creative junior investigators and trainees provides a structure to achieve these common goals. To this end, the structure provided by cancer-focused educational programs can create the integrated culture of academic medicine needed to reduce the burden of cancer on society. This summary outlines fundamental principles and potential best practice strategies for the development of integrated educational programs directed at achieving a work force of professionals that broadly appreciate the principals of academic medicine spanning the breadth of knowledge necessary to advance the goal of improving the current practice of cancer care medicine.

Abstract 3264: Genome-wide shRNA screen identifies ITIH5 gene as a metastasis suppressor of pancreatic ductal adenocarcinoma (PDAC)

Background: PDAC is a leading cause of cancer-related death worldwide, and most patients have incurable disease at diagnosis. Life expectancy is only 3-6 months post-diagnosis, ostensibly due to early dissemination to liver and other vital organs. Results: By transfecting a shRNA library into non-metastatic PDAC line S2-028 followed by experimental metastasis assay, ITIH5 was identified. Metastatic PDAC cell lines (e.g., S2-007, MIAPaCa-2, Panc-1) had significantly lower ITIH5 protein expression compared to immortalized pancreatic ductal epithelial cells and non-/poorly-metastatic PDAC cell lines (e.g., S2-028 and BxPC3). By manipulating expression in different PDAC cell lines (over-expression in S2-007 and MIAPaCa-2, knockdown in non-metastatic S2-028 with two different shRNA) functional and selective regulation of metastasis was observed. Orthotopic tumor growth of PDAC cells was not blocked. Thus ITIH5 qualifies as a metastasis suppressor. Overexpression of ITIH5 significantly inhibited invasion and migration, while down-regulation increased these cellular properties. Immunohistochemistry of a human PDAC tissue microarray (n = 81) revealed that negative expression of ITIH5 showed significantly higher incidence of liver metastasis (P = 0.0482) corresponding with worse prognosis after surgery (P = 0.0299). Conclusions: ITIH5 is a potent metastasis suppressor with suggestive prognostic value in PDAC. Future studies will continue to characterize biochemical properties of ITIH5, identify interaction partners, and investigate the molecular mechanism(s) of action. Support: National Foundation for Cancer Research, Steiner Family Fund and CA168524.

Citation Format: Ken Sasaki, Hiroshi Kurahara, S Natsugoe, Tomoo Iwakuma, Danny R. Welch. Genome-wide shRNA screen identifies ITIH5 gene as a metastasis suppressor of pancreatic ductal adenocarcinoma (PDAC). [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 3264. doi:10.1158/1538-7445.AM2015-3264

Abstract 3253: Metastasis suppression by non-KP54 kisspeptins

The KISS1 metastasis suppressor blocks metastasis by inhibiting colonization at secondary sites. KISS1 activity requires secretion and extracellular processing by furin into kisspeptins. Kisspeptin-54 (KP54; G68 to F121) binds a G-protein coupled receptor, KISS1R, and the mechanism of metastasis suppression has been assumed to be through the receptor. However, KISS1 is cleaved into kisspeptins outside of the cell, and KISS1R expression is not required for metastasis suppression. Therefore, an alternate hypothesis is that a non-KISS1R binding kisspeptin(s) is responsible for metastasis suppression. To test this hypothesis, we engineered all ten of the possible kisspeptins predicted from known dibasic cleavage sites (M1-Q145; M1-R56; M1-R67; M1-R124; R56-R67; G68-F121; E55-F121; E55-Q145; G68-Q145; E125-Q145) downstream of the KISS1 secretion signal peptide (designated KMP1 to KMP10, respectively) and expressed each individually in B16-F10 melanoma cells. Expression was confirmed by immunoblot and/or RT-QPCR analysis. Following intravenous injection, experimental lung metastases were quantified. KP54 expression suppressed metastasis. Some KMP lacking the KISS1R ligand suppressed metastasis as well as KP54 and full-length KISS1 (p<0.05). Specifically, the N-terminal kisspeptin (M1 - R56) dramatically suppressed metastasis. This suggests that the mechanism of action for metastasis suppression by KISS1 does not necessarily require activation of KISS1R by the peptide ligand but also leaves the possibility for additional receptors. Alternatively, KISS1/KMP interactions with other intracellular proteins may be required for metastasis suppressor activity. Support: CA134981, Natl Fndn Cancer Res, Komen SAC11037, KS Bioscience Auth, P30-CA168524, Steiner Family Fund.

Citation Format: Kelsey R. Hampton, Keke M. Pounds, Andrew P. Tremblath, Danny R. Welch. Metastasis suppression by non-KP54 kisspeptins. [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 3253. doi:10.1158/1538-7445.AM2015-3253

Abstract 3258: Breast Metastasis Suppressor 1 (BRMS1) phosphorylation appears necessary for metastasis suppressor activity

Breast cancer is the most common cancer among women worldwide. BRMS1 is a metastasis suppressor that suppresses metastasis without significantly affecting the growth of a primary tumor. BRMS1 contains two coiled-coil motifs important for protein-protein interactions and two putative nuclear localization sequences (NLS - aa198-205 (NLS1) and aa239-245 (NLS2)) and one nuclear export signal which appear to mediate nuclear-cytoplasmic shuttling. Although NLS2 is not necessary for active transport into the nucleus, it is required for metastasis suppression (PMC3563580). A serine immediately upstream of NLS2 (S237) can be phosphorylated by cdk2 (PMC3037622). Therefore, we hypothesized that NLS2 and adjacent amino acids are critical mediators of metastasis suppression. To test this hypothesis, NLS2 (aa231-248) epitope-tagged with HA and GST was transduced into metastatic MDA-MB-231 and -435 breast carcinoma cells expressing green fluorescent protein and stable colonies were selected. BRMS1S237A-expressing MDA-MB-231 cells were no longer metastasis suppressed, suggesting a critical role for phosphorylation of BRMS1 in its metastasis suppressor activity. Studies are underway with full-length BRMS1S237D (phosphomimetic) as well as expression with truncated wild-type NLS2 and mutant (NLS2wt/S237A/S237D) to test whether the BRMS1 phosphorylation or the NLS2 domain itself is critical for metastasis suppressor activity. Support: CA87728, CA134981, P30-CA168524, Natl Fndn Cancer Res, Komen SAC11037, KS Bioscience Auth, NHMRC

Citation Format: Lellys M. Contreras, Boris Sarcevic, Keke M. Pounds, Danny R. Welch. Breast Metastasis Suppressor 1 (BRMS1) phosphorylation appears necessary for metastasis suppressor activity. [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 3258. doi:10.1158/1538-7445.AM2015-3258

Abstract 5128: Changes in mitochondrial background affect nuclear DNA methylation

There is emerging evidence demonstrating that mitochondrial DNA (mtDNA) contributes to complex genetic diseases such as cancer. To test directly the role of mtDNA in tumorigenicity and metastasis, a new genetically engineered mouse model was created that contains nuclear DNA from one mouse strain and mtDNA contribution from different mouse strain(s). Taking advantage of maternal inheritance, Mitochondrial Nuclear Exchange (MNX) mice can be bred to mice sharing the same nuclear DNA background. As a result, MNX serves as an important tool to determine if and how mitochondrial genetic background contributes to cancer, negating the concern for mixing maternal and paternal nuclear DNA polymorphisms. MNX mice are healthy, breed normally, show no overt differences in cell cycle or apoptosis and are genetically stable for multiple (>10) generations. Nonetheless, they are distinct strains based upon behaviors and gene expression patterns. The mechanisms controlling gene expression in different MNX strains are not yet known; however, retrograde and anterograde cross-talk exists between the nuclear and mitochondrial genomes. Our hypothesis is that important epigenetic changes occur in the nuclear genome depending upon mitochondrial genetics. To test this hypothesis, we performed Meth-Seq using the Agilent Mouse SureSelect platform and Affymetrix gene expression arrays on four mouse brains (8 wk) that were pooled from different litters and cages of wild-type and MNX to minimize age, developmental, inter-individual and generational heterogeneity. Both differential DNA methylation and gene expression patterns were observed but analyses are ongoing to better define the observed differences. Together these observations provide novel insights into how mtDNA could be altering epigenetic regulation and thereby contribute to cancer pathogenesis. Support: Susan G. Komen for the Cure (SAC11037), Natl Fndn Cancer Res., Kansas Bioscience Authority, Steiner Family Fund.

Citation Format: Carolyn J. Vivian, Amanda E. Brinker, Gerald C. Gooden, Christophe Legendre, Bodour Salhia, Danny R. Welch. Changes in mitochondrial background affect nuclear DNA methylation. [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 5128. doi:10.1158/1538-7445.AM2015-5128

Abstract 2338: Histone demethylase KDM3A: Epigenetic target for pancreatic ductal adenocarcinoma (PDAC)

Purpose: A growing body of evidence suggests that cancer stem cells/tumor initiating cells (CSC/TIC) within a solid tumor including in pancreatic cancer initiate and sustain tumor growth. Our preliminary data implicates KDM3A (histone lysine demethylase 3A)/Jmjd1A (jumonji domain demethylase 1A), non-heme iron (II)- α-ketoglutarate (kg) dependent enzyme, as a prime regulator of stems cell self-renewability for cancer progression and is overexpressed in PDAC. Hypoxia most prominently controls malignant properties of cancer cells by stimulating hypoxia inducible factor 1 (HIF1). The fact that HIF1 binds to its responsible elements (HREs) in the KDM3A promoters and subsequently up-regulates its expression could explain why hypoxia exacerbates malignancy. Based on these observations, we hypothesize that hypoxia induces KDM3A that regulates self-renewability of CSC/TIC, thereby promoting tumor initiation.

Experimental Procedure: We have used RNA technology to silence KDM3A in different pancreatic cancer cells and overexpressed KDM3A in non-cancerous immortal pancreatic ductal epithelial cells (HPNE). We have determined KDM3A expression in pancreatic cancer patient's samples. We performed quantitative chromatin immunoprecipitation (ChIP) analysis as an indicator of KDM3A recruitment.

Results: KDM3A was overexpressed in human pancreatic cancer patient tissue samples particularly in the area of the pancreatic ducts and also in pancreatic cancer cells. Knockdown of KDM3A in pancreatic cancer cells significantly reduced the enzyme activity resulting in increased substrate (H3K9Me2) expression. KDM3A knockdown cells decreased oncogenic potential as demonstrated by inhibition of proliferation, clonogenicity, sphere-forming potential, migration and tumor formation in orthotopic mouse model (immunocompromised mice). KDM3A overexpressed transformed HPNE cells increased oncogenic potential as evidenced by foci formation, pancosphere formation and tumor formation in orthotopic mouse model. ChIP following deep sequencing analysis suggested that KDM3A recruited one of the CSC stem cell markers, DCLK1. N-oxaloglycine, α-kg inhibitor, inhibited KDM3A enzyme activity and spheroid formation in overexpressing HPNE cells and in pancreatic cancer cells.Conclusions: KDM3A was overexpressed in PDAC. ChIP-seq analysis revealed that KDM3A recruitment was higher when DCLK1 is expressed. Taken together, KDM3A appears to be responsible, at least in part, for PDAC progression and could be a novel preventive or therapeutic target in pancreatic cancer.

Citation Format: Satheesh K. Sainathan, Santanu Paul, Kanagaraj Palaniyandi, Dharmalingam Subramaniam, Satish Ramalingam, Ossama W. Tawfik, Tomoo Iwakuma, Danny R. Welch, Subhash B. Padhye, Shrikant Anant, Animesh Dhar. Histone demethylase KDM3A: Epigenetic target for pancreatic ductal adenocarcinoma (PDAC). [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 2338. doi:10.1158/1538-7445.AM2015-2338