Mehner, Christine

Ovarian cancer remains a devastating disease with 5 year survival rate in advanced stage of only 27%. Advanced stage tumors metastasize through continuous shedding of tumor cells into the peritoneal fluid, aided by the resistance of these cells to anoikis, a form of apoptosis normally triggered by loss of cell‐matrix interactions. We have previously shown that the serine protease inhibitor SPINK1 activates anoikis resistance in ovarian cancer cells via its protease inhibitory function; however, the specific relevant protease target(s) remain unknown. To find these targets, we have synthesized an activity‐based protein probe with a diphenylphosphonate warhead that covalently modifies serine proteases, with greatest specificity towards trypsin‐like proteases. We have used this probe to identify ovarian cancer cell secreted and membrane‐bound serine proteases possessing differential activity in the presence versus absence of SPINK1, using a proteomics approach. We are evaluating candidate proteases for involvement in anoikis resistance in ovarian cancer models. Our studies implicate a serine protease network in regulation of anoikis in ovarian cancer cells. By identifying critical proteases that control anchorage‐independent viability in ovarian cancer metastasis, we aim to elucidate important downstream pathways and ultimately develop therapeutic approaches that can intervene in mechanisms of anoikis resistance. Support or Funding Information Mayo Clinic Graduate School, Rochester MN

With the advancement in reusable rocket propulsion technology, space tourist trips into outer space are now becoming a possibility at a cost-effective rate. As such, astronauts will face a host of health-related challenges, particularly on long-duration space missions where maintaining a balanced healthy microbiome is going to be vital for human survival in space exploration as well as mission success. The human microbiome involves a whole list of micro-organisms that reside in and on the human host, and plays an integral role in keeping the human host healthy. However, imbalances in the microbiome have been directly linked to many human diseases. Research findings have clearly shown that the outer space environment can directly affect the normal microbiome of astronauts when the astronaut is exposed to the microgravity environment. In this study, we show that the simulation of microgravity on earth can mimic the outer space microgravity environment. Staphylococus aureus (S. aureus) was chosen for this study as it is an opportunistic pathogen, which is part of the normal human skin microflora and the nasal passages. This study’s results show that S. aureus proliferation was significantly increased under a microgravity environment compared to Earth’s gravity conditions, which complements previous work performed on bacteria in the outer space environment in the International Space Station (ISS). This demonstrates that this technology can be utilised here on Earth to mimic the outer space environment and to study challenging health-related questions. This in return saves us the cost on conducting experiments in the ISS and can help advance knowledge at a faster rate and produce countermeasures to mitigate the negative side effects of the hostile outer space environment on humans.

AbstractGlioblastoma multiforme (GBM) is one of the most aggressive malignant brain tumors and urgently requires the development of new therapeutic strategies. In this study, an innovative hybrid in vitro vascularized GBM‐on‐a‐chip model is presented as a strategic integration of microfluidics and 3D bioprinting technologies. The system can recreate the compartmentalized brain tumor microenvironment, comprising the functional blood brain barrier (BBB) and the adjacent 3D perivascular tumor niche, by selectively mimicking physiological shear stress and cell–cell, cell–matrix mechanical interaction. The GBM‐on‐a‐chip model was evaluated under simulated microgravity (µG) condition as a form of mechanical unloading showing a significant cell morphological and mechanotransduction response thereby indicating that gravitational forces play an important role in glioblastoma mechanical regulation. The proposed GBM‐on‐a‐chip represents a meaningful biological tool for further research in cancer mechanobiology and pre‐clinical approach in brain tumor therapy.

Abstract Ovarian cancer remains a challenging disease, with an average 5 year survival rate of 46%. At time of diagnosis, over 70% of patients have advanced metastatic disease, for which there are no effective treatment options. Of patients with metastatic disease, more than 70% of patients develop peritoneal carcinomatosis, making the peritoneum one of the main areas of dissemination. We have previously found that expression of the serine protease inhibitor Kazal type 1 (SPINK1) by ovarian cancer cells drives anoikis resistance, allowing the tumor cells to circumvent apoptosis protocols and facilitating tumor cell metastasis. For this new study we focused on ovarian clear cell carcinoma (OCCC), a histotype of ovarian cancer that has particularly poor prognosis if diagnosed in late stage. Using OCCC cell lines, we found that knockdown of SPINK1 reduces cell survival and stimulates apoptotic pathways in OCCC cells, when cultured under attachment-free conditions to mimic metastatic disease. We then identified Interleukin-6 (IL-6) as an upstream regulator of SPINK1 expression and a potential therapeutic target for metastatic OCCC: we showed that IL-6 silencing reduced SPINK1 mRNA expression and cell survival, while treatment with recombinant IL-6 increased SPINK1 expression and attachment-free survival. We developed a new OCCC mouse model and showed that knockdown of SPINK1 results in significant reduction of metastatic lesions, highlighting the impact of SPINK1 on OCCC metastasis. In ongoing studies we are testing intraperitoneal injections of FDA approved IL-6 inhibitors in a preclinical model to assess impact on abdominal dissemination of tumor cells. By targeting the IL-6 – SPINK1 signaling axis, we aim to develop therapeutic approaches to reduce the metastatic burden and peritoneal carcinomatosis of late stage disease, resulting in better prognosis and survival of patients with ovarian clear cell carcinoma. Citation Format: Christine Mehner, Erin Miller, Mathew A. Coban, Alexandra Hockla, Derek C. Radisky, Evette S. Radisky. Targeting ovarian cancer induced peritoneal carcinomatosis by inhibition of signaling axis between Interleukin-6 (IL-6) and serine protease inhibitor Kazal type 1 (SPINK1) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3758.

Abstract Patients diagnosed with ovarian cancer face an average 5 year survival rate of 46%; low survival is driven by early and ongoing intraperitoneal dissemination and metastasis of the tumor. Among the different histotypes of ovarian cancer, ovarian clear cell carcinoma (OCCC) has a particularly poor prognosis when diagnosed in late stage, as these tumors tend to be chemoresistant, leaving no effective therapeutic options. Intraperitoneal metastasis requires cells to become anoikis resistant, where apoptosis normally induced by loss of attachment is suppressed. We seek to better understand the mechanisms involved in anoikis resistance in OCCC, which in the future could lead to new therapeutic strategies for these patients. We have found that Serine Protease Inhibitor Kazal type 1 (SPINK1), an endogenous inhibitor of trypsin like serine proteases, is also an important regulator of anoikis resistance in some ovarian cancers. In this study, we aimed to dissect the role of SPINK1 specifically in OCCC, defining its contribution to anoikis resistance using cultured OCCC cell lines and elucidating its mechanism of action. We compared anoikis resistance of cells with endogenous SPINK1 expression versus cells in which SPINK1 was silenced using lentiviral shRNA constructs, when culturing cells on ultra-low attachment plates to mimic cell detachment from the extracellular matrix. We found that knockdown of SPINK1 reduced survival and stimulated apoptotic pathways in OCCC cells grown under detached conditions, implicating SPINK1 in anoikis resistance of OCCC cells. As a secreted protease inhibitor, SPINK1 may be expected to confer anoikis resistance by inhibiting an extracellular serine protease involved in triggering anoikis. Because many proteases represent potential targets of SPINK1, we have designed a strategy using Activity Based Protein Profiling (ABPP) to discover the targets of SPINK1 from among this large pool of candidates. In pilot studies, we have successfully used a novel activity-based probe to covalently label the active sites of serine proteases secreted from OCCC cells. In ongoing efforts, we are optimizing methods to identify labeled proteases with high sensitivity using tandem mass spectrometry. We will then identify those proteases regulated by SPINK1 through comparison of labeled proteomes from OCCC cells with and without SPINK1 treatment,, and candidate proteases will be further analyzed for their role in triggering anoikis. The identification of SPINK1 regulated proteases that are responsible for mediating anoikis in our models will give insight into important mechanisms whereby tumor cells acquire resistance to anoikis in OCCC. In-depth understanding of anoikis resistance, a critical component of ovarian cancer progression and metastasis, may lead to novel biomarkers of disease progression as well as important therapeutic targets. Citation Format: Christine Mehner, Mathew A. Coban, Alexandra Hockla, Derek C. Radisky, Evette S. Radisky. Serine protease inhibitor Kazal type 1 (SPINK1) drives anoikis resistance in ovarian clear cell carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 442.

Abstract Benign breast disease, a known risk factor for subsequent breast cancer, includes a histological spectrum of lesions that can be subdivided based on the overall impression into non-proliferative lesions, proliferative lesions without atypia, and atypical hyperplasia. Yet little is known about the molecular characteristics of benign breast tissue from African American women, who suffer from disproportionately high breast cancer mortality rates. 72 breast samples from African American women were obtained. RNA was extracted from archival formalin-fixed, paraffin-embedded (FFPE) blocks. Gene expression profiling was performed on these samples using the Affymetrix HTA2.0 exon array chip. A fit linear model using generalized least squares identified probe sets with differential expression in benign-in situ and benign-invasive breast cancer paired lesions. 36 benign and 36 breast cancer paired lesions were included in the study. In the benign-in situ set (n=20), 978 probe sets were differentially expressed (threshold: fold-change, 1.50; p < 0.05). Probe sets mapped to 125 annotated genes, of which 69 (55.2%) were involved in cancer. The benign-invasive set (n=52) identified 351 differentially expressed probe sets that mapped to 84 annotated genes, of which 61 (72.6%) had known cancer significance. Genes involved in cellular growth and proliferation were significantly over-expressed in both benign-in situ and benign-invasive lesions (p-values < 0.0104). In the population of 36 paired samples, differentially expressed genes were found to regulate the estrogen receptor (ESR1) through distinct network associations. Many genes are differentially expressed by benign and breast cancer lesions, and in situ/invasive histology contribute to the distinct molecular characteristics and pathways of breast malignancy. Our findings highlight the first study to assess expression profiling of paired benign and breast cancer lesions among African American women. Citation Format: Andreana Natalie Holowatyj, Julie J. Ruterbusch, Rouba Ali-Fehmi, Sudeshna Bandyopadhyay, Christine Mehner, Melody Stallings Mann, Gregory Dyson, Derek Radisky, Michele L. Cote. Expression profiling of paired benign and breast cancer lesions in African American women [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 4253. doi:10.1158/1538-7445.AM2017-4253

AbstractThe Hippo pathway effector YAP is implicated in the pathogenesis of cholangiocarcinoma (CCA). The Hippo pathway relies on signaling cross talk for its regulation. Given the importance of platelet derived growth factor receptor (PDGFR) signaling in CCA biology, our aim was to examine potential YAP regulation by PDGFR. We employed human and mouse CCA specimens and cell lines for these studies. Initially, we confirmed upregulation of PDGFRβ and PDGFR ligands in human and mouse CCA specimens and cell lines. YAP, a transcriptional co‐activator, was localized to the nucleus in human CCA specimens and a cell line, as well as patient derived xenografts (PDX). PDGFR pharmacologic inhibition led to a redistribution of YAP from the nucleus to cytosol and downregulation of YAP target genes in a human CCA cell line. siRNA silencing of PDGFR‐β similarly downregulated YAP target genes. YAP activation (nuclear localization and target gene expression) was regulated by Src family kinases (SFKs) downstream of PDGFR. SFK activity resulted in phosphorylation of YAP on tyrosine357 (YAPY357). The importance of YAPY357 phosphorylation in regulating YAP activation was confirmed utilizing the SB‐1 cell line, a mouse cell line expressing YAP S127A precluding canonical serine phosphorylation. PDGFR inhibition decreased cellular abundance of the survival protein Mcl‐1, a known YAP target gene, and accordingly increased cell death in CCA cells in vitro and in vivo. These preclinical data demonstrate that a PDGFR‐SFK cascade regulates YAP activation via tyrosine phosphorylation in CCA. Inhibiting this cascade may provide a viable therapeutic strategy for this human malignancy.

Abstract Basal subtype breast cancers have a particularly poor prognosis, with high invasiveness and resistance to most targeted therapies. TGFβ and MYC drive central features of basal breast cancer: TGFβ is an autocrine and paracrine signaling factor that drives cell invasion and metastasis, and MYC is a central regulator of cellular proliferation that is upregulated in many cancer types. We show here that genetic or pharmacologic inhibition of MYC in MCF10A basal breast cells results in increased sensitivity to TGFβ-stimulated invasion and metastasis and also show that this signaling loop is dependent on activation of SRC. Analysis of human breast cancer datasets and additional experiments with breast cancer cell lines further suggest the relevance of this signaling loop in basal, but not luminal, breast cancers. Our results imply precaution should be taken when utilizing therapeutic inhibitors of MYC with basal breast cancer patients as this could lead to increased metastasis; however, simultaneous pharmacologic inhibition of SRC and MYC for these patients could facilitate the antiproliferative effects of MYC inhibition while blocking the consequent promotion of metastasis. Cancer Res; 76(12); 3520–30. ©2016 AACR.