Aging Increases Susceptibility to Ovarian Cancer Metastasis in Murine Allograft Models and Alters Immune Composition of Peritoneal Adipose Tissue

Ovarian cancer, the most deadly gynecological malignancy in U.S. women, metastasizes uniquely, spreading through the peritoneal cavity and often generating widespread metastatic sites before diagnosis. The vast majority of ovarian cancer cases occur in women over 40 and the median age at diagnosis is 63. Additionally, elderly women receive poorer prognoses when diagnosed with ovarian cancer. Despite age being a significant risk factor for the development of this cancer, there are little published data which address the impact of aging on ovarian cancer metastasis. Here we report that the aged host is more susceptible to metastatic success using two murine syngeneic allograft models of ovarian cancer metastasis. This age-related increase in metastatic tumor burden corresponds with an increase in tumor infiltrating lymphocytes (TILs) in tumor-bearing mice and alteration of B cell-related pathways in gonadal adipose tissue. Based on this work, further studies elucidating the status of B cell TILs in mouse models of metastasis and human tumors in the context of aging are warranted.

Multiparity activates interferon pathways in peritoneal adipose tissue and decreases susceptibility to ovarian cancer metastasis in a murine allograft model

Ovarian cancer is the fifth leading cause of cancer deaths in U.S. women and the deadliest gynecologic malignancy. This lethality is largely due to the fact that most cases are diagnosed at metastatic stages of the disease when the prognosis is poor. Epidemiologic studies consistently demonstrate that parous women have a reduced risk of developing ovarian cancer, with a greater number of births affording greater protection; however little is known about the impact of parity on ovarian cancer metastasis. Here we report that multiparous mice are less susceptible to ovarian cancer metastasis in an age-matched syngeneic murine allograft model. Interferon pathways were found to be upregulated in healthy adipose tissue of multiparous mice, suggesting a possible mechanism for the multiparous-related protective effect against metastasis. This protective effect was found to be lost with age. Based on this work, future studies exploring therapeutic strategies which harness the multiparity-associated protective effect demonstrated here are warranted.

Abstract TMEM-025: IMPACT OF MESOTHELIN EXPRESSION ON THE METASTATIC SUCCESS OF OVARIAN CANCER

Ovarian cancer is the most lethal gynecological cancer in U.S. women. Poor 5-year survival rates (<30%) are due to presentation of most women at diagnosis with advanced stage disease with widely disseminated intraperitoneal metastasis. However, when diagnosed before metastatic propagation the overall 5-year survival rate is >90%. Metastasizing tumor cells grow rapidly and aggressively attach to the mesothelium of all organs within the peritoneal cavity, including the parietal peritoneum and the omentum, producing secondary lesions. Mesothelin (MSLN), a 40kDa glycoprotein that is over expressed in many cancers including ovarian and mesotheliomas is suggested to play a role in cell survival, proliferation, tumor progression and adherence. However, the biological function of mesothelin is not fully understood as MSLN knockout mice do not present with an abnormal phenotype. Conversely, MSLN has been shown to bind to the ovarian cancer antigen, CA-125, and thought to play a role in the peritoneal diffusion of ovarian tumor cells. Taking into consideration the potential importance of MSLN/CA-125 binding in ovarian tumor metastasis within the peritoneum, MSLN wild type (WT) and knockout (KO) mice were used to explore the role of mesothelin on the susceptibility of ovarian tumor cells to adhere to the mesothelium of the organs in the peritoneal cavity. An ex vivo peritoneal assay, using CA-125 positive human ovarian tumor cells OVCAR8-GFP and peritoneal explants from MSLN WT and KO mice demonstrated a decrease in OVCAR8-GFP cell adhesion to peritoneal tissues from MSLN KO mice compared to MSLN WT mice. Furthermore, allograft tumor studies using MSLN WT and KO mice injected intraperitoneally with fluorescently-tagged syngeneic murine ovarian cancer cells (ID8-RFP) was performed. Disease progression was evaluated post injection by fluorescent in vivo imaging prior to end point dissection (~8 weeks). Abdominal organs were dissected, imaged ex vivo and organ-specific tumor burden was quantified by tumor area. Tumor burden was significantly decreased in the liver and omentum of MSLN KO mice compared to MSLN WT mice. Together, the results demonstrate a loss of mesothelial cell-ovarian tumor cell adhesion in the omentum and peritoneum of mice that do not express MSLN.

Citation Format: Tyvette Hilliard, Kyle Iwamoto, Elizabeth Loughran, Marwa Asem, Yueying Liu, Jing Yang, Laura Tarwater, Yuliya Klymenko, Jeff Johnson, Zonggao Shi, and M. Sharon Stack. IMPACT OF MESOTHELIN EXPRESSION ON THE METASTATIC SUCCESS OF OVARIAN CANCER [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr TMEM-025.

Abstract TMEM-029: AGING INCREASES SUSCEPTIBILITY TO OVARIAN CANCER METASTASIS IN A MURINE ALLOGRAFT MODEL

Ovarian cancer (OvCa) is the leading gynecological malignancy in women in the United States. OvCa metastasizes uniquely, spreading through the peritoneal cavity and generating widespread metastatic sites. The vast majority of OvCa cases occur in women over 40 and the median age at diagnosis is 63 (SEER). Despite age being a significant risk factor for the development of OvCa, there is a paucity of studies addressing the role of aging in OvCa metastasis. To our knowledge, there are no reports utilizing old mice to investigate the effects of age on metastasis in vivo. We designed a study using a C57BL/6 model of aging where young (Y) mice are 3-6 months of age and aged (A) mice are 20-23 months of age, corresponding to young (20-30 years) and aged (60-67 years) humans. Using the C57BL/6 syngeneic ID8 mouse ovarian surface epithelial cell line, we tested the effect of aging on metastatic success in vivo. An allograft study was carried out with Y and A mice that were intraperitoneally injected with 3.7x106 ID8 RFP-tagged cells. The mice were imaged once a week starting at 4.5 weeks post injection and were sacrificed for dissection at 8 weeks post injection. Live imaging suggested OvCa metastasis was more efficient in the aged animals than in the young animals. After dissection, the abdominal organs were imaged ex vivo and tumor burden was quantified. The aged mice displayed heavier tumor burden in the gonadal fat compared to the young. Interestingly, no difference in metastasis to the omentum was detected. To investigate why gonadal fat is more receptive to metastasis in the aged animals, periovarian adipose from 4 young and 4 aged healthy non-tumor bearing mice was isolated for RNAseq analysis. Several immune pathways involving B cells were found to be significantly upregulated in the RNA from aged animals. Studies will be conducted to elucidate the status of B cells in aging periovarian adipose, including immunohistochemistry for CD45 and other B cell markers upregulated in the RNAseq dataset.

Citation Format: Elizabeth Loughran, Annemarie Leonard, Ryan Phan, Laura Tarwater, Tyvette Hilliard, Marwa Asem, Yueying Liu, Jing Yang, Yuliya Klymenko, Jeff Johnson, Zonggao Shi, Matthew Leevy, Matthew Ravosa and M. Sharon Stack. AGING INCREASES SUSCEPTIBILITY TO OVARIAN CANCER METASTASIS IN A MURINE ALLOGRAFT MODEL [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr TMEM-029.

Protease-activated Receptor-2 (PAR-2)-mediated Nf-κB Activation Suppresses Inflammation-associated Tumor Suppressor MicroRNAs in Oral Squamous Cell Carcinoma

Oral cancer is the sixth most common cause of death from cancer with an estimated 400,000 deaths worldwide and a low (50%) 5-year survival rate. The most common form of oral cancer is oral squamous cell carcinoma (OSCC). OSCC is highly inflammatory and invasive, and the degree of inflammation correlates with tumor aggressiveness. The G protein-coupled receptor protease-activated receptor-2 (PAR-2) plays a key role in inflammation. PAR-2 is activated via proteolytic cleavage by trypsin-like serine proteases, including kallikrein-5 (KLK5), or by treatment with activating peptides. PAR-2 activation induces G protein-α-mediated signaling, mobilizing intracellular calcium and Nf-κB signaling, leading to the increased expression of pro-inflammatory mRNAs. Little is known, however, about PAR-2 regulation of inflammation-related microRNAs. Here, we assess PAR-2 expression and function in OSCC cell lines and tissues. Stimulation of PAR-2 activates Nf-κB signaling, resulting in RelA nuclear translocation and enhanced expression of pro-inflammatory mRNAs. Concomitantly, suppression of the anti-inflammatory tumor suppressor microRNAs let-7d, miR-23b, and miR-200c was observed following PAR-2 stimulation. Analysis of orthotopic oral tumors generated by cells with reduced KLK5 expression showed smaller, less aggressive lesions with reduced inflammatory infiltrate relative to tumors generated by KLK5-expressing control cells. Together, these data support a model wherein KLK5-mediated PAR-2 activation regulates the expression of inflammation-associated mRNAs and microRNAs, thereby modulating progression of oral tumors.

Abstract B67: The impact of parity on the metastatic success of ovarian cancer

Ovarian cancer is the most fatal gynecological cancer. Epithelial ovarian cancer (OvCa), the most common subtype, usually goes undetected until metastatic and often fatal stages of the disease. OvCa follows a unique form of metastasis, spreading through the peritoneal cavity and forming metastatic sites on the peritoneum. Epidemiologic data suggest that child-bearing, or parity, reduces a woman's risk of developing ovarian cancer, with more births providing greater protection. Despite the association of parity with a decreased incidence of ovarian cancer, very few studies have explored the relationship between parity and metastatic success. A recent study compared metastatic success to the omentum in 12-month-old C57Bl/6 retired breeders and 5-month-old virgin mice, reporting that parous mice are less susceptible to metastasis due to the parity-associated differences in the immune compositional profile in the omental fat band (Cohen et al. 2013). This tumor study compared mice of different ages and did not report specific numbers of pregnancies. To further investigate the role of parity number in OvCa metastasis, we designed a study that controls for age and compares mice with specific parity number. Three age-matched C57Bl/6 groups were evaluated: nulliparous (V), parous 1 (P1), and parous 3 (P3) mice. We tested the effect of parity on metastatic success in vivo with an allograft study using the C57Bl/6 syngeneic ID8 mouse ovarian surface epithelial cell line. ID8 ovarian cancer cells (106) were injected into the peritoneal cavity of V, P1 and P3 mice. In contrast to the results of Cohen at al. that utilized a different syngeneic ovarian cancer cell line, we found no significant difference in metastasis to the omentum in the parous animals, but significantly reduced metastasis to the fat-enveloped ovaries and visceral fat pads in the P3 mice. This suggests that the visceral fat adjacent to the uterus and ovaries in multi-parous animals is a unique environment, resilient to metastasis. Factors in fat tissue responsible for this phenomenon are being investigated.

Citation Format: Elizabeth A. Loughran, Ryan Phan, Annemarie K. Leonard, Laura Tarwater, Marwa Asem, Yuliya Klymenko, Yueying Liu, Jing Yang, Jeff Johnson, Matthew Ravosa, M. Sharon Stack. The impact of parity on the metastatic success of ovarian cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr B67.

Obesity Contributes to Ovarian Cancer Metastatic Success through Increased Lipogenesis, Enhanced Vascularity, and Decreased Infiltration of M1 Macrophages

Epithelial ovarian cancer (EOC) is the leading cause of death from gynecologic malignancy, with high mortality attributable to widespread intraperitoneal metastases. Recent meta-analyses report an association between obesity, ovarian cancer incidence, and ovarian cancer survival, but the effect of obesity on metastasis has not been evaluated. The objective of this study was to use an integrative approach combining in vitro, ex vivo, and in vivo studies to test the hypothesis that obesity contributes to ovarian cancer metastatic success. Initial in vitro studies using three-dimensional mesomimetic cultures showed enhanced cell-cell adhesion to the lipid-loaded mesothelium. Furthermore, in an ex vivo colonization assay, ovarian cancer cells exhibited increased adhesion to mesothelial explants excised from mice modeling diet-induced obesity (DIO), in which they were fed a "Western" diet. Examination of mesothelial ultrastructure revealed a substantial increase in the density of microvilli in DIO mice. Moreover, enhanced intraperitoneal tumor burden was observed in overweight or obese animals in three distinct in vivo models. Further histologic analyses suggested that alterations in lipid regulatory factors, enhanced vascularity, and decreased M1/M2 macrophage ratios may account for the enhanced tumorigenicity. Together, these findings show that obesity potently affects ovarian cancer metastatic success, which likely contributes to the negative correlation between obesity and ovarian cancer survival.