Katharine M. Bendt

Epstein-Barr virus LMP2A transforms epithelial cells, inhibits cell differentiation, and activates Akt

ABSTRACT The Epstein-Barr virus LMP2A protein was expressed in a human keratinocyte cell line, HaCaT, and effects on epithelial cell growth were detected in organotypic raft cultures and in vivo in nude mice. Raft cultures derived from LMP2A-expressing cells were hyperproliferative, and epithelial differentiation was inhibited. The LMP2A-expressing HaCaT cells were able to grow anchorage independently and formed colonies in soft agar. HaCaT cells expressing LMP2A were highly tumorigenic and formed aggressive tumors in nude mice. The LMP2A tumors were poorly differentiated and highly proliferative, in contrast to occasional tumors that arose from parental HaCaT cells and vector control cells, which grew slowly and remained highly differentiated. Animals injected with LMP2A-expressing cells developed frequent metastases, which predominantly involved lymphoid organs. Involucrin, a marker of epithelial differentiation, and E-cadherin, involved in the maintenance of intercellular contact, were downregulated in LMP2A tumors. Whereas activation of the mitogen-activated protein kinase pathway was not observed, phosphatidylinositol-3-kinase (PI3-kinase)-dependent activation of the serine-threonine kinase Akt was detected in LMP2A-expressing cells and LMP2A tumors. Inhibition of this pathway blocked growth in soft agar. These data indicate that LMP2A greatly affects cell growth and differentiation pathways in epithelial cells, in part through activation of the PI3-kinase–Akt pathway.

LMP1 signaling and activation of NF-κB in LMP1 transgenic mice

Transgenic mice expressing Epstein–Barr virus (EBV) latent membrane protein 1 (LMP1) under the control of an immunoglobulin heavy-chain promoter and enhancer develop lymphoma at a threefold higher incidence than LMP1-negative mice. In vitro, LMP1 activates numerous signaling pathways including p38, c-Jun N terminal kinase (JNK), phosphatidylinositol 3 kinase (PI3K)/Akt, and NF-κB through interactions with tumor necrosis receptor-associated factors (TRAFs). These pathways are frequently activated in EBV-associated malignancies, although their activation cannot be definitively linked to LMP1 expression in vivo. In this study, interactions between LMP1 and TRAFs and the activation of PI3K/Akt, JNK, p38, and NF-κB were examined in LMP1 transgenic mice. LMP1 co-immunoprecipitated with TRAFs 1, 2, and 3. Akt, JNK, and p38 were activated in LMP1-positive and -negative splenocytes as well as LMP1-positive and -negative lymphomas. Multiple forms of NF-κB were activated in healthy splenocytes from LMP1 transgenic mice, in contrast to healthy splenocytes from LMP1-negative mice. However, in both LMP1-positive and -negative lymphomas, only the oncogenic NF-κB c-Rel, was specifically activated. Similarly to EBV-associated malignancies, p53 protein was detected at high levels in the transgenic lymphomas, although mutations were not detected in the p53 gene. These data indicate that NF-κB is activated in LMP1-positive healthy splenocytes; however, NF-κB c-Rel is specifically activated in both the transgenic lymphomas and in the rare lymphomas that develop in negative mice. The LMP1-mediated activation of NF-κB may contribute to the specific activation of c-Rel and lead to the increased development of lymphoma in the LMP1 transgenic mice.

Transfection of α(1,3)fucosyltransferase antisense sequences impairs the proliferative and tumorigenic ability of human colon carcinoma cells

Sialyl Lewis x and sialyl Lewis a are oncodevelopmental antigens involved in the pathogenesis of colon adenocarcinoma. Biosynthesis of these glycans is controlled by α(1,3/1,4)fucosyltransferases. We report the disruption of sialyl Lewis x/a biosynthesis and inhibition of colon carcinoma cell proliferation by stable transfection of antisense sequences directed at the human Lewis α(1,3/1,4)fucosyltransferase gene, FUT3, and the plasma α(1,3)fucosyltransferase gene, FUT6. COLO‐205 cells expressed high levels of sialyl Lewis x/a, α(1,3)fucosyltransferase activity, and FUT3/6 transcripts, but COLO

Epstein-Barr Virus-Encoded Latent Membrane Protein 1 (LMP1) and LMP2A Function Cooperatively To Promote Carcinoma Development in a Mouse Carcinogenesis Model

ABSTRACT The Epstein-Barr virus (EBV) proteins latent membrane proteins 1 and 2 (LMP1 and LMP2) are frequently expressed in EBV-associated lymphoid and epithelial cancers and have complex effects on cell signaling and growth. The effects of these proteins on epithelial cell growth were assessed in vivo using transgenic mice driven by the keratin 14 promoter (K14). The development of papillomas and carcinomas was determined in the tumor initiator and promoter model using dimethyl benzanthracene (DMBA), followed by repeated treatments of 12-O-tetradecanoyl phorbol 13-acetate (TPA). In these assays, LMP1 functioned as a weak tumor promoter and increased papilloma formation. In contrast, mice expressing LMP2A did not induce or promote papilloma formation. Transgenic LMP1 mice had slightly increased development of squamous cell carcinoma; however, the development of carcinoma was significantly increased in the doubly transgenic mice expressing both LMP1 and LMP2A. DMBA treatment induces an activating mutation in the Harvey-ras (H-ras 61 ) oncogene, and this mutation was identified in most papillomas and carcinomas although several papillomas and carcinomas in K14-LMP1 and K14-LMP1/LMP2A mice lacked the mutation. Analysis of signaling pathways that are known to be activated by LMP1 and/or LMP2 indicated that all genotypes had high levels of activated extracellular signal-regulated kinase (ERK) and Stat3 in carcinomas with significantly higher activation in the doubly transgenic carcinomas. These findings suggest that, in combination, LMP1 and LMP2 contribute to carcinoma progression and that this may reflect the combined effects of the proteins on activation of multiple signaling pathways. This study is the first to characterize the effects of LMP2 on tumor initiation and promotion and to identify an effect of the combined expression of LMP1 and LMP2 on the increase of carcinoma development.

Role of HGF in obesity-associated tumorigenesis: C3(1)-TAg mice as a model for human basal-like breast cancer.

Obesity is associated with basal-like breast cancer (BBC), an aggressive breast cancer subtype. The objective of this study was to determine whether obesity promotes BBC onset in adulthood and to evaluate the role of stromal–epithelial interactions in obesity-associated tumorigenesis. We hypothesized that hepatocyte growth factor (HGF) plays a promoting role in BBC, which express the HGF receptor, c-Met. In C3(1)-TAg mice, a murine model of BBC, we demonstrated that obesity leads to a significant increase in HGF secretion and an associated decrease in tumor latency. By immunohistochemical analysis, normal mammary gland exhibited obesity-induced HGF, c-Met and phospho-c-Met, indicating that the activation of the cascade was obesity-driven. HGF secretion was also increased from primary mammary fibroblasts isolated from normal mammary glands and tumors of obese mice compared to lean. These results demonstrate that obesity-induced elevation of HGF expression is a stable phenotype, maintained after several passages, and after removal of dietary stimulation. Conditioned media from primary tumor fibroblasts from obese mice drove tumor cell proliferation. In co-culture, neutralization of secreted HGF blunted tumor cell migration, further linking obesity-mediated HGF-dependent effects to in vitro measures of tumor aggressiveness. In sum, these results demonstrate that HGF/c-Met plays an important role in obesity-associated carcinogenesis. Understanding the effects of obesity on risk and progression is important given that epidemiologic studies imply a portion of BBC could be eliminated by reducing obesity.

Weight Loss Reversed Obesity-Induced HGF/c-Met Pathway and Basal-Like Breast Cancer Progression

Epidemiologic studies demonstrate that obesity is associated with an aggressive subtype of breast cancer called basal-like breast cancer (BBC). Using the C3(1)-TAg murine model of BBC, we previously demonstrated that mice displayed an early onset of tumors when fed obesogenic diets in the adult window of susceptibility. Obesity was also shown to elevate mammary gland expression and activation of hepatocyte growth factor (HGF)/c-Met compared to lean controls, a pro-tumorigenic pathway associated with BBC in patients. Epidemiologic studies estimate that weight loss could prevent a large proportion of BBC. We sought to investigate whether weight loss in adulthood prior to tumor onset would protect mice from accelerated tumorigenesis observed in obese mice. Using a life-long model of obesity, C3(1)-TAg mice were weaned onto and maintained on an obesogenic high-fat diet. Obese mice displayed significant elevations in tumor progression, but not latency or burden. Tumor progression was significantly reversed when obese mice were induced to lose weight by switching to a control low-fat diet prior to tumor onset compared to mice maintained on obesogenic diet. We investigated the HGF/c-Met pathway known to regulate tumorigenesis. Importantly, HGF/c-Met expression in normal mammary glands and c-Met in tumors was elevated with obesity and was significantly reversed with weight loss. Changes in tumor growth could not be explained by measures of HGF action including phospho-AKT or phospho-S6. Other mediators associated with oncogenesis such as hyperinsulinemia and a high leptin:adiponectin ratio were elevated by obesity and reduced with weight loss. In sum, weight loss significantly blunted the obesity-responsive pro-tumorigenic HGF/c-Met pathway and improved several metabolic risk factors associated with BBC, which together may have contributed to the dramatic reversal of obesity-driven tumor progression. Future research aims to evaluate the role of obesity and the HGF/c-Met pathway in basal-like breast cancer progression.

Obesity-Mediated Regulation of HGF/c-Met Is Associated with Reduced Basal-Like Breast Cancer Latency in Parous Mice

It is widely thought that pregnancy reduces breast cancer risk, but this lacks consideration of breast cancer subtypes. While a full term pregnancy reduces risk for estrogen receptor positive (ER+) and luminal breast cancers, parity is associated with increased risk of basal-like breast cancer (BBC) subtype. Basal-like subtypes represent less than 10% of breast cancers and are highly aggressive, affecting primarily young, African American women. Our previous work demonstrated that high fat diet-induced obesity in nulliparous mice significantly blunted latency in C3(1)-TAg mice, a model of BBC, potentially through the hepatocyte growth factor (HGF)/c-Met oncogenic pathway. Experimental studies have examined parity and obesity individually, but to date, the joint effects of parity and obesity have not been studied. We investigated the role of obesity in parous mice on BBC. Parity alone dramatically blunted tumor latency compared to nulliparous controls with no effects on tumor number or growth, while obesity had only a minor role in further reducing latency. Obesity-associated metabolic mediators and hormones such as insulin, estrogen, and progesterone were not significantly regulated by obesity. Plasma IL-6 was also significantly elevated by obesity in parous mice. We have previously reported a potential role for stromal-derived hepatocyte growth factor (HGF) via its cognate receptor c-Met in the etiology of obesity-induced BBC tumor onset and in both human and murine primary coculture models of BBC-aggressiveness. Obesity-associated c-Met concentrations were 2.5-fold greater in normal mammary glands of parous mice. Taken together, our studies demonstrate that, parity in C3(1)-TAg mice dramatically reduced BBC latency compared to nulliparous mice. In parous mice, c-Met is regulated by obesity in unaffected mammary gland and is associated with tumor onset. C3(1)-TAg mice recapitulate epidemiologic findings such that parity drives increased BBC risk and potential microenvironmental alterations in c-Met signaling may play a role in etiology.

Abstract 4871: Obesity-mediated regulation of HGF/c-Met and reduced basal-like breast cancer latency in parous mice

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Background: Epidemiologic and experimental data have shown that a full term pregnancy reduces breast cancer risk. While a full term pregnancy reduces risk for estrogen receptor positive (ER+) and luminal breast cancers, parity is associated with increased risk of basal-like breast cancer (BBC) subtype. BBC represents <10% of breast cancers, are highly aggressive, affecting primarily young and African-American women. Experimental studies have examined parity and obesity individually, but to date, the independent and joint effects of parity and obesity have not been dissected. Our previous work demonstrated that high fat diet-induced obesity significantly blunted BBC latency in nulliparous C3(1)-Tag mice, potentially through the hepatocyte growth factor (HGF)/c-Met oncogenic pathway. Since obesity and post-partum weight gain are sometimes difficult to parse out, we investigated the role of obesity in parous mice on BBC. Methods: Seven week old female C3(1)-TAg mice were placed with male mice for breeding. Males were removed at pregnancy and pups were removed immediately after birth. The mothers were then randomly assigned to diet groups to model post-partum obesity. Mice were fed control low fat diet (10% kcal from fat) or high fat diet (45% or 60% kcal from fat) at 10 weeks until sacrifice. Mice were monitored for fat accretion, tumor onset, and tumor progression. Plasma measures of cytokines and metabolic parameters were assessed. Immunohistochemical analyses for HGF, c-Met and F4/80 macrophage markers were performed. Results: Mice on both 45% and 60% diets gained significantly greater fat mass compared to mice remaining lean on 10% diet. Compared with nulliparous mice fed the same diets, parity induced significant decreases in latency in C3(1)-TAg mice fed 10% and 45% diets. 60% diet reduced latency in parous mice to the same extent as nulliparous mice fed 60% diet. Tumor burden and tumor aggressiveness were not regulated by obesity in parous mouse. Obesity-associated metabolic mediators and hormones such as insulin, estrogen, and progesterone were not significantly regulated however, leptin levels were elevated in 45%-fed mice compared to other groups. Plasma IL-6 was significantly elevated by obesity in parous mice. Importantly, the HGF/c-Met axis in normal mammary gland was elevated significantly by obesity and correlated with reduced tumor latency. Conclusions: In summary, our studies demonstrate that, similar to epidemiologic reports, parity in C3(1)-TAg mice alone dramatically reduced BBC latency compared to nulliparous mice. Obesity in parous mice did not reduce latency further than obesity alone, indicating that obesity and parity may work through similar pathways. Finally, obesity induced c-Met expression in normal mammary gland in parous mice, similar to our reports in nulliparous mice, implicating an interaction between the HGF/c-Met signaling pathway and obesity in the etiology of BBC. Citation Format: Sneha Sundaram, Alex J. Freemerman, Erin L. Kirk, Joseph A. Galanko, Kirk K. McNaughton, Katharine M. Bendt, David B. Darr, Melissa A. Troester, Liza Makowski. Obesity-mediated regulation of HGF/c-Met and reduced basal-like breast cancer latency in parous mice. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4871. doi:10.1158/1538-7445.AM2014-4871

Abstract P4-04-28: Weight loss reversed the carcinogenic effect of obesity on basal-like breast cancer

Epidemiologic studies demonstrate that obesity is associated with a subtype of breast cancer called basal-like breast cancer (BBC), which is fast proliferating and aggressive, with no targeted therapies. Using the C3(1)-T Ag murine model of BBC, we have previously shown that obese adult mice displayed significantly decreased tumor latency compared to lean mice with induction of the oncogenic HGF/c-Met pathway. Reducing adiposity is predicted to lower incidence of BBC in human population studies. Thus, the objective of this study was to investigate how a diet-switch to reduce obesity affected BBC onset and early progression. C3(1)-T Ag mice were placed on a control low fat diet (LFD) and remained lean, high-fat diet (HFD) to induce obesity, and a group made obese by HFD that were then switched to LFD to induce weight loss. Just two weeks after weight loss, mice in the diet switch group had weights and adiposity similar to lean mice. Weight loss caused a 51.4% decrease in adiposity (P Citation Format: Yuanyuan Qin, Sneha Sundaram, Liyang Zhao, Luma Essaid, Kirk K McNaughton, Katharine M Bendt, David B Darr, Melissa A Troester, Liza Makowski. Weight loss reversed the carcinogenic effect of obesity on basal-like breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-04-28.

Abstract 5040: Weight loss prevents obesity-associated basal-like breast cancer progression: Role of hepatocyte growth factor/c-Met

Background: Epidemiologic studies demonstrate that obesity-associated basal-like breast cancer is an aggressive subtype and as a triple negative subtype, no targeted therapies are currently available. Basal-like breast cancer (BBC) is often diagnosed in young and African American women. Using a murine model of BBC, C3(1)-TAg, we previously reported that like humans, mice made obese in adulthood displayed an early onset of tumors. Obesity also elevated mammary gland expression and activation of the pro-tumorigenic hepatocyte growth factor (HGF) and its cognate receptor (c-Met) pathway compared to lean controls. We sought to investigate whether weight loss prior to tumor onset would protect mice from accelerated tumorigenesis and elevations in HGF/c-Met pathway. Methods: C3(1)-TAg mice were fed a high fat diet (60% kcal from fat) at weaning and became obese compared to control mice fed a low fat diet (10% kcal from fat). Weight loss was induced through a diet intervention: obese mice on 60% diet were switched to 10% at 10 weeks of age. Mice were monitored for fat mass accretion, tumor onset, and tumor progression. At sacrifice, various tissues were collected and plasma measures of cytokines and metabolic parameters were assessed. Immunohistochemical analyses for HGF, c-Met and F4/80 macrophage markers were performed. Results: C3(1)-TAg mice fed 60% diet displayed significant elevations in body weight and body fat composition which were reversed to control levels after two weeks after switching to 10% dietof weight loss. Tumor latency or burden were not altered but obesity dramatically regulated tumor aggressiveness. Obese C3(1)-TAg mice displayed significant elevations in tumor promotiongrowth, which were reversed to control levels when obese mice lost weight. Importantly, the HGF/c-Met axis was also elevated by obesity and reversed restored to control levels uponwith weight loss. Other obesity-associated parameters such as hyperinsulinemia and leptin/adiponectin ratio were elevated in obese mice and reduced with weight loss. Although systemic inflammatory cytokines were not significantly altered by obesity or weight loss, macrophage infiltration into the normal mammary gland was significantly elevated in obese mice with a decrease to control levels observed following weight loss. Conclusions: In sum, weight loss reversed obesity-driven tumor aggressiveness promotion and blunted the obesity-responsive pro-tumorigenic HGF/c-Met pathway, as well as improved several metabolic and inflammatory risk factors associated with BBC. Citation Format: Sneha Sundaram, Trinh Le, Luma Essaid, Kirk K. McNaughton, Katharine M. Bendt, David B. Darr, Melissa A. Troester, Liza Makowski. Weight loss prevents obesity-associated basal-like breast cancer progression: Role of hepatocyte growth factor/c-Met. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5040. doi:10.1158/1538-7445.AM2014-5040