Dichotomous ovarian cancer-initiating potential of Pax8+ cells revealed by a mouse genetic mosaic model.

Different cellular compartments within a tissue present distinct cancer-initiating capacities. Current approaches to dissect such heterogeneity require cell-type-specific genetic tools based on a well-understood lineage hierarchy, which are lacking for many tissues. Here, we circumvented this hurdle and revealed the dichotomous capacity of fallopian tube Pax8+ cells in initiating ovarian cancer, utilizing a mouse genetic system that stochastically generates rare GFP-labeled mutant cells. Through clonal analysis and spatial profiling, we determined that only clones founded by rare, stem/progenitor-like Pax8+ cells can expand on acquiring oncogenic mutations whereas vast majority of clones stall immediately. Furthermore, expanded mutant clones undergo further attrition: many turn quiescent shortly after the initial expansion, whereas others sustain proliferation and manifest a bias toward Pax8+ fate, underlying early pathogenesis. Our study showcases the power of genetic mosaic system-based clonal analysis for revealing cellular heterogeneity of cancer-initiating capacity in tissues with limited prior knowledge of lineage hierarchy.

Notch3 signaling promotes tumor cell adhesion and progression in a murine epithelial ovarian cancer model.

High grade serous ovarian cancer (HGSC) is the most common and deadly type of ovarian cancer, largely due to difficulties in early diagnosis and rapid metastasis throughout the peritoneal cavity. Previous studies have shown that expression of Notch3 correlates with worse prognosis and increased tumorigenic cell behaviors in HGSC. We investigated the mechanistic role of Notch3 in a model of metastatic ovarian cancer using the murine ovarian surface epithelial cell line, ID8 IP2. Notch3 was activated in ID8 IP2 cells via expression of the Notch3 intracellular domain (Notch3IC). Notch3IC ID8 IP2 cells injected intraperitoneally caused accelerated ascites and reduced survival compared to control ID8 IP2, particularly in early stages of disease. We interrogated downstream targets of Notch3IC in ID8 IP2 cells by RNA sequencing and found significant induction of genes that encode adhesion and extracellular matrix proteins. Notch3IC ID8 IP2 showed increased expression of ITGA1 mRNA and cell-surface protein. Notch3IC-mediated increase of ITGA1 was also seen in two human ovarian cancer cells. Notch3IC ID8 IP2 cells showed increased adhesion to collagens I and IV in vitro. We propose that Notch3 activation in ovarian cancer cells causes increased adherence to collagen-rich peritoneal surfaces. Thus, the correlation between increased Notch3 signaling and poor prognosis may be influenced by increased metastasis of HGSC via increased adherence of disseminating cells to new metastatic sites in the peritoneum.

Plectin-targeted liposomes enhance the therapeutic efficacy of a PARP inhibitor in the treatment of ovarian cancer.

Advances in genomics and proteomics drive precision medicine by providing actionable genetic alterations and molecularly targeted therapies, respectively. While genomic analysis and medicinal chemistry have advanced patient stratification with treatments tailored to the genetic profile of a patient's tumor, proteomic targeting has the potential to enhance the therapeutic index of drugs like poly(ADP-ribose) polymerase (PARP) inhibitors. PARP inhibitors in breast and ovarian cancer patients with BRCA1/2 mutations have shown promise. About 10% of the patients who received Olaparib (PARP inhibitor) showed adverse side effects including neutropenia, thrombocytopenia and in some cases resulted in myelodysplastic syndrome, indicating that off-target effects were substantial in these patients. Through proteomic analysis, our lab previously identified plectin, a cytolinker protein that mislocalized onto the cell surface during malignant transformation of healthy ovarian tissue. This cancer specific phenotype allowed us to image pancreatic cancer successfully using plectin targeted peptide (PTP) conjugated to nanoparticles or displayed on capsid protein of adeno-associated virus (AAV) particles. Objective: The goal of this study was to integrate the available pharmacogenomics and proteomic data to develop effective anti-tumor therapies using a targeted drug delivery approach. Methods: Plectin expression and localization in human ovarian tumor specimens were analyzed followed by in vitro confirmation of cell surface plectin localization in healthy and ovarian cancer cell lines. PTP-conjugated liposomes were prepared and their specificity for plectin+ cells was determined in vitro and in vivo. A remote loading method was employed to encapsulate a PARP inhibitor (AZ7379) into liposomes. An ideal buffer exchange method and remote loading conditions were determined based on the amount of lipid and drug recovered at the end of a remote loading process. Finally, in vivo tumor growth studies were performed to determine the efficacy of PTP liposomes in preventing PARP activity in mice bearing OVCAR8 (high grade epithelial ovarian cancer (EOC)) tumors. Results: PTP liposomal AZ7379 delivery not only enhanced PARP inhibition but also resulted in decelerated tumor growth in mice bearing subcutaneous and intraperitoneal OVCAR8 tumors. In mice bearing subcutaneous or intraperitoneal tumors, treatment with PTP liposomes resulted in a 3- and 1.7-fold decrease in tumor volume, respectively, compared to systemic drug treatment. Conclusion: Targeted drug delivery assisted by genomic and proteomic data provides an adaptable model system that can be extended to effectively treat other cancers and diseases.

Inhibition of hepatic lipogenesis enhances liver tumorigenesis by increasing antioxidant defence and promoting cell survival.

The metabolic pathway of de novo lipogenesis is frequently upregulated in human liver tumours, and its upregulation is associated with poor prognosis. Blocking lipogenesis in cultured liver cancer cells is sufficient to decrease cell viability; however, it is not known whether blocking lipogenesis in vivo can prevent liver tumorigenesis. Herein, we inhibit hepatic lipogenesis in mice by liver-specific knockout of acetyl-CoA carboxylase (ACC) genes and treat the mice with the hepatocellular carcinogen diethylnitrosamine (DEN). Unexpectedly, mice lacking hepatic lipogenesis have a twofold increase in tumour incidence and multiplicity compared to controls. Metabolomics analysis of ACC-deficient liver identifies a marked increase in antioxidants including NADPH and reduced glutathione. Importantly, supplementing primary wild-type hepatocytes with glutathione precursors improves cell survival following DEN treatment to a level indistinguishable from ACC-deficient primary hepatocytes. This study shows that lipogenesis is dispensable for liver tumorigenesis in mice treated with DEN, and identifies an important role for ACC enzymes in redox regulation and cell survival.

Mesothelium expression of vascular cell adhesion molecule-1 (VCAM-1) is associated with an unfavorable prognosis in epithelial ovarian cancer (EOC).

BACKGROUND: Mesothelium vascular cell adhesion molecule-1 (VCAM-1) expression in the metastatic epithelial ovarian cancer (EOC) microenvironment is induced by tumor and mediates tumor cell invasion. VCAM-1 imaging suggests expression during treatment is an indicator of platinum resistance. Here, we assess the potential prognostic significance of mesothelium VCAM-1 expression and prospectively evaluate whether soluble VCAM-1 (sVCAM-1) is a surrogate for mesothelium expression. METHODS: A retrospective review of EOC patients was performed to evaluate outcomes with mesothelium VCAM-1 expression determined by immunohistochemistry of peritoneum or omentum specimens. A prospective cohort of EOC patients was identified and followed through primary treatment. Serum for sVCAM-1 evaluation, which was performed via enzyme-linked immunosorbent assay, was collected before surgery or neoadjuvant chemotherapy and at each treatment cycle. Peritoneal specimens were obtained during debulking to assess mesothelial VCAM-1 expression. RESULTS: A retrospective review identified 54 advanced-stage EOC patients. Patients expressing mesothelium VCAM-1 had shortened overall survival (44 vs 79 months, P = 0.035) and progression-free survival (18 vs 67 months, P = 0.010); the median time to platinum resistance was 36 months for VCAM-1-expressing patients and not yet determined for the VCAM-1-negative group. In our prospective observational cohort, 18 EOC patients completed primary treatment; 3 were negative for mesothelium VCAM-1 expression, and sVCAM-1 did not vary between groups. CONCLUSIONS: Mesothelium VCAM-1 expression is negatively associated with progression-free and overall survival in EOC. This is especially compelling in light of previous data suggesting that persistent VCAM-1 expression during treatment is an indicator of platinum resistance. Our pilot study had insufficient cases to determine whether sVCAM-1 would substitute for mesothelium expression. Cancer 2017;123:977-84. © 2016 American Cancer Society.

Lysophosphatidic acid counteracts glucagon-induced hepatocyte glucose production via STAT3.

Hepatic glucose production (HGP) is required to maintain normoglycemia during fasting. Glucagon is the primary hormone responsible for increasing HGP; however, there are many additional hormone and metabolic factors that influence glucagon sensitivity. In this study we report that the bioactive lipid lysophosphatidic acid (LPA) regulates hepatocyte glucose production by antagonizing glucagon-induced expression of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK). Treatment of primary hepatocytes with exogenous LPA blunted glucagon-induced PEPCK expression and glucose production. Similarly, knockout mice lacking the LPA-degrading enzyme phospholipid phosphate phosphatase type 1 (PLPP1) had a 2-fold increase in endogenous LPA levels, reduced PEPCK levels during fasting, and decreased hepatic gluconeogenesis in response to a pyruvate challenge. Mechanistically, LPA antagonized glucagon-mediated inhibition of STAT3, a transcriptional repressor of PEPCK. Importantly, LPA did not blunt glucagon-stimulated glucose production or PEPCK expression in hepatocytes lacking STAT3. These data identify a novel role for PLPP1 activity and hepatocyte LPA levels in glucagon sensitivity via a mechanism involving STAT3.

Lobular Breast Cancer and Abdominal Metastases: A Retrospective Review and Impact on Survival.

BACKGROUND: The predominant breast cancer subtypes, invasive lobular carcinoma (ILC) and invasive ductal carcinoma (IDC), have similar recurrence and survival rates but differing patterns of metastatic recurrence. METHODS: A retrospective review of breast cancers treated at an academic medical center from 1999 to 2012 was performed. Demographic, pathologic, treatment, and follow-up data were collected for 179 ILC and 358 IDC patients (1:2 stage-matched). The median follow-up was 4.7 years. RESULTS: The baseline characteristics were similar in the two groups. ILC was more likely to be hormone-receptor-positive/HER2-negative and mammographically occult. The number of surgical resections, breast conservation rate, systemic treatment, and taxane use was similar between the groups. The overall recurrence rate was the same. ILC recurred more often in the abdominal cavity (24.3% in ILC vs. 4.1% in IDC, p = 0.001). The disease-free survival and overall survival were equal. On multivariate analysis, age, stage of disease, hormone receptor status, and systemic therapy were associated with survival, but histology was not. CONCLUSIONS: Compared to ductal breast cancers, lobular breast cancers recur more often in the abdominal cavity. Both ILC and IDC have comparable surgical and medical treatment outcomes and survival. Our data suggest that enhanced surveillance and imaging might be useful in ILC.

T-Type Ca2+ Channel Inhibition Sensitizes Ovarian Cancer to Carboplatin.

Ovarian cancer is the deadliest gynecologic cancer, due in large part to the diagnosis of advanced stage disease, the development of platinum resistance, and inadequate treatment alternatives. Recent studies by our group and others have shown that T-type calcium (Ca(2+)) channels play a reinforcing role in cancer cell proliferation, cell-cycle progression, and apoptosis evasion. Therefore, we investigated whether T-type Ca(2+) channels affect ovarian tumor growth and response to platinum agents. Inhibition of T-type Ca(2+) channels with mibefradil or by silencing expression resulted in growth suppression in ovarian cancer cells with a simultaneous increase in apoptosis, which was accompanied by decreased expression of the antiapoptotic gene survivin (BIRC5). Analysis of intracellular signaling revealed mibefradil reduced AKT phosphorylation, increased the levels and nuclear retention of FOXO transcription factors that repress BIRC5 expression, and decreased the expression of FOXM1, which promotes BIRC5 expression. Combining carboplatin with mibefradil synergistically increased apoptosis in vitro. Importantly, mibefradil rendered platinum-resistant ovarian tumors sensitive to carboplatin in a mouse model of peritoneal metastasis. Together, the data provide rationale for future use of T-type channel antagonists together with platinum agents for the treatment of ovarian cancer.

Women at extreme risk for obesity-related carcinogenesis: Baseline endometrial pathology and impact of bariatric surgery on weight, metabolic profiles and quality of life.

OBJECTIVES: The study objectives were to determine baseline endometrial histology in morbidly obese women undergoing bariatric surgery and to assess the surgical intervention's impact on serum metabolic parameters, quality of life (QOL), and weight. METHODS: Women undergoing bariatric surgery were enrolled. Demographic and clinicopathologic data, serum, and endometrium (if no prior hysterectomy) were collected preoperatively and serum collected postoperatively. Serum global biochemical data were assessed pre/postoperatively. Welch's two sample t-tests and paired t-tests were used to identify significant differences. RESULTS: Mean age of the 71 women enrolled was 44.2 years, mean body mass index (BMI) was 50.9 kg/m(2), and mean weight loss was 45.7 kg. Endometrial biopsy results: proliferative (13/30; 43%), insufficient (8/30; 27%), secretory (6/30; 20%) and hyperplasia (3/30; 10%-1 complex atypical, 2 simple). QOL data showed significant improvement in physical component scores (PCS means 33.9 vs. 47.2 before/after surgery; p<0.001). Twenty women underwent metabolic analysis which demonstrated significantly improved glucose homeostasis, improved insulin responsiveness, and free fatty acid levels. Significant perturbations in tryptophan, phenylalanine and heme metabolism suggested decreased inflammation and alterations in the intestinal microbiome. Most steroid hormones were not significantly impacted with the exception of decreased DHEAS and 4-androsten metabolites. CONCLUSIONS: Bariatric surgery is accompanied by an improved physical quality of life as well as beneficial changes in glucose homeostasis, insulin responsiveness, and inflammation to a greater extent than the hormonal milieu. The potential cancer protective effects of bariatric surgery may be due to other mechanisms other than simply hormonal changes.

Decreased peritoneal ovarian cancer growth in mice lacking expression of lipid phosphate phosphohydrolase 1.

Lysophosphatidic acid (LPA) is a bioactive lipid that enhances ovarian cancer cell proliferation, migration and invasion in vitro and stimulates peritoneal metastasis in vivo. LPA is generated through the action of autotaxin or phospholipases, and degradation begins with lipid phosphate phosphohydrolase (LPP)-dependent removal of the phosphate. While the effects of LPA on ovarian cancer progression are clear, the effects of LPA metabolism within the tumor microenvironment on peritoneal metastasis have not been reported. We examined the contribution of lipid phosphatase activity to ovarian cancer peritoneal metastasis using mice deficient in LPP1 expression. Homozygous deletion of LPP1 (LPP1 KO) results in elevated levels and decreased turnover of LPA in vivo. Within 2 weeks of intraperitoneal injection of syngeneic mouse ovarian cancer cells, we observed enhanced tumor seeding in the LPP1 KO mice compared to wild type. However, tumor growth plateaued in the LPP1 KO mice by 3 weeks while tumors continued to grow in wild type mice. The decreased tumor burden was accompanied by increased apoptosis and no change in proliferation or angiogenesis. Tumor growth was restored and apoptosis reversed with exogenous administration of LPA. Together, these observations demonstrate that the elevated levels of LPA per se in LPP1 KO mice do not inhibit tumor growth. Rather, the data support the notion that either elevated LPA concentration or altered LPA metabolism affects other growth-promoting contributions of the tumor microenvironment.

VCAM-1 on peritoneum and α4ß1 integrin in endometrium and their implications in endometriosis.

The objective of the study is to investigate vascular cellular adhesion molecule-1 (VCAM-1) expression on peritoneal mesothelial cells and α4ß1 integrin on eutopic endometrium as possible mechanisms in the pathogenesis of endometriosis. It is a case-control study carried out at an academic medical center. Participants are patients with (n=9) and without (n=15) endometriosis. The main outcome measures included VCAM-1 expression on peritoneal mesothelial cells and α4ß1 expression on eutopic endometrium using immunohistochemistry and flow cytometry, respectively. Patients with endometriosis were more likely to express VCAM-1 on peritoneal mesothelial cells, both in areas with and without macroscopic disease, compared with patients without endometriosis (9/9 vs. 3/15, P<0.001). No differences were found between cases and controls in regards to eutopic endometrial expression of α4ß1 integrin. The presence of VCAM-1 on peritoneal mesothelial cells is associated with endometriosis. This field effect, in addition to the similarity found with regards to the expression of α4ß1 integrin in eutopic endometrium between cases and controls, may implicate the expression of VCAM-1 in the peritoneum, and not changes in the eutopic endometrium, as a contributor to the pathogenesis of endometriosis.

Metabolic vulnerabilities in endometrial cancer.

Women with metabolic disorders, including obesity and diabetes, have an increased risk of developing endometrial cancer. However, the metabolism of endometrial tumors themselves has been largely understudied. Comparing human endometrial tumors and cells with their nonmalignant counterparts, we found that upregulation of the glucose transporter GLUT6 was more closely associated with the cancer phenotype than other hallmark cancer genes, including hexokinase 2 and pyruvate kinase M2. Importantly, suppression of GLUT6 expression inhibited glycolysis and survival of endometrial cancer cells. Glycolysis and lipogenesis were also highly coupled with the cancer phenotype in patient samples and cells. To test whether targeting endometrial cancer metabolism could be exploited as a therapeutic strategy, we screened a panel of compounds known to target diverse metabolic pathways in endometrial cells. We identified that the glycolytic inhibitor, 3-bromopyruvate, is a powerful antagonist of lipogenesis through pyruvylation of CoA. We also provide evidence that 3-bromopyruvate promotes cell death via a necrotic mechanism that does not involve reactive oxygen species and that 3-bromopyruvate impaired the growth of endometrial cancer xenografts.

Inhibition of α4ß1 integrin increases ovarian cancer response to carboplatin.

OBJECTIVE: The inability to successfully treat women with ovarian cancer is due to the presence of metastatic disease at diagnosis and the development of platinum resistance. Ovarian cancer metastasizes throughout the peritoneal cavity by attaching to and invading through the mesothelium lining the peritoneum using a mechanism that involves α4ß1 integrin and its ligand (vascular cell adhesion molecule) VCAM-1. Integrin α4ß1 expression on tumor cells is known to confer protection from therapy in other cancers, notably multiple myeloma. We evaluated the role of α4ß1 integrin in response to platinum-based therapy in a mouse model of peritoneal ovarian cancer metastasis by treatment with a humanized anti-α4ß1 integrin function-blocking antibody. METHODS: Integrin α4ß1 expression on primary human ovarian cancer cells, fallopian tube and ovarian surface epithelia and fresh tumor was assessed by flow-cytometry. The therapeutic impact of anti-α4ß1 treatment was assessed in murine models of platinum-resistant peritoneal disease and in vitro using the platinum resistant ovarian cancer cell lines. RESULTS: Treatment of tumor-bearing mice with human-specific α4ß1 integrin function-blocking antibodies, anti-VCAM-1 antibody or carboplatin alone had no effect on tumor burden compared to the IgG control group. However, the combined treatment of anti-α4ß1 integrin or anti-VCAM-1 with carboplatin significantly reduced tumor burden. In vitro, the combination of carboplatin and anti-α4ß1 integrin antibodies resulted in increased cell death and doubling time. CONCLUSIONS: Our findings support a role for α4ß1 integrin in regulating treatment response to carboplatin, implicating α4ß1 integrin as a potential therapeutic target to influence platinum responsiveness in otherwise resistant disease.

Imaging VCAM-1 as an indicator of treatment efficacy in metastatic ovarian cancer.

UNLABELLED: The inability to successfully treat women with ovarian cancer is due in large part to the advanced stage of disease at diagnosis, the development of platinum resistance, and the lack of sensitive methods to monitor tumor progression and response to treatment. Vascular cell adhesion molecule-1 (VCAM-1) is expressed on the mesothelium of ovarian cancer patients. We investigated VCAM-1 expression as a marker of peritoneal metastasis and tumor response to platinum-based chemotherapy. METHODS: Peritoneal or omental biopsies obtained from women diagnosed with stage I, stage II, or stage III/IV ovarian cancer were evaluated by immunohistochemistry. The effects of carboplatin on mesothelial VCAM-1 expression were determined in cultured cells by Western blot. Radiolabeled VCAM-1-specific peptide imaging probes and SPECT were used in a mouse model of ovarian cancer peritoneal metastasis to identify VCAM-1 as a viable imaging target. RESULTS: VCAM-1 expression correlated with tumor stage. All specimens from stage I patients were negative, whereas 29% of stage II patients and 73% of stage III/IV patients were positive. Although most women with advanced stage disease expressed VCAM-1, the incidence of expression was reduced among women who received neoadjuvant chemotherapy, suggesting a role for chemotherapy in regulating VCAM-1 expression. Treatment of mesothelial cells in culture with carboplatin resulted in a transient decrease in VCAM-1 expression 4 h after treatment that returned to baseline within 16-24 h. In vivo imaging of VCAM-1 also demonstrated an acute decrease in expression 4 h after carboplatin administration that recovered within 48 h in mice harboring platinum-resistant tumors. Chronic VCAM-1 expression reflected the effect of platinum-based treatment on tumor burden. Specifically, carboplatin treatment of mice with platinum-sensitive tumors showed reduced VCAM-1 expression, which correlated with reduced tumor burden; mice with platinum-resistant tumors retained elevated VCAM-1 expression and tumor burden after treatment. CONCLUSION: Clinically relevant VCAM-1-specific imaging probes identify VCAM-1 expression as an indicator of ovarian cancer peritoneal metastasis and therapeutic response to platinum-based agents. These observations support testing the utility of VCAM-1 imaging probes to monitor treatment response in ovarian cancer patients, thus providing the potential to improve management of women with this disease.

Inhibition of focal adhesion kinase by PF-562,271 inhibits the growth and metastasis of pancreatic cancer concomitant with altering the tumor microenvironment.

Current therapies for pancreatic ductal adenocarcinoma (PDA) target individual tumor cells. Focal adhesion kinase (FAK) is activated in PDA, and levels are inversely associated with survival. We investigated the effects of PF-562,271 (a small-molecule inhibitor of FAK/PYK2) on (i) in vitro migration, invasion, and proliferation; (ii) tumor proliferation, invasion, and metastasis in a murine model; and (iii) stromal cell composition in the PDA microenvironment. Migration assays were conducted to assess tumor and stromal cell migration in response to cellular factors, collagen, and the effects of PF-562,271. An orthotopic murine model was used to assess the effects of PF-562,271 on tumor growth, invasion, and metastasis. Proliferation assays measured PF-562,271 effects on in vitro growth. Immunohistochemistry was used to examine the effects of FAK inhibition on the cellular composition of the tumor microenvironment. FAK and PYK2 were activated and expressed in patient-derived PDA tumors, stromal components, and human PDA cell lines. PF-562,271 blocked phosphorylation of FAK (phospho-FAK or Y397) in a dose-dependent manner. PF-562,271 inhibited migration of tumor cells, cancer-associated fibroblasts, and macrophages. Treatment of mice with PF-562,271 resulted in reduced tumor growth, invasion, and metastases. PF-562,271 had no effect on tumor necrosis, angiogenesis, or apoptosis, but it did decrease tumor cell proliferation and resulted in fewer tumor-associated macrophages and fibroblasts than control or gemcitabine. These data support a role for FAK in PDA and suggest that inhibitors of FAK may contribute to efficacious treatment of patients with PDA.

Matrix rigidity regulates cancer cell growth and cellular phenotype.

BACKGROUND: The mechanical properties of the extracellular matrix have an important role in cell growth and differentiation. However, it is unclear as to what extent cancer cells respond to changes in the mechanical properties (rigidity/stiffness) of the microenvironment and how this response varies among cancer cell lines. METHODOLOGY/PRINCIPAL FINDINGS: In this study we used a recently developed 96-well plate system that arrays extracellular matrix-conjugated polyacrylamide gels that increase in stiffness by at least 50-fold across the plate. This plate was used to determine how changes in the rigidity of the extracellular matrix modulate the biological properties of tumor cells. The cell lines tested fall into one of two categories based on their proliferation on substrates of differing stiffness: "rigidity dependent" (those which show an increase in cell growth as extracellular rigidity is increased), and "rigidity independent" (those which grow equally on both soft and stiff substrates). Cells which grew poorly on soft gels also showed decreased spreading and migration under these conditions. More importantly, seeding the cell lines into the lungs of nude mice revealed that the ability of cells to grow on soft gels in vitro correlated with their ability to grow in a soft tissue environment in vivo. The lung carcinoma line A549 responded to culture on soft gels by expressing the differentiated epithelial marker E-cadherin and decreasing the expression of the mesenchymal transcription factor Slug. CONCLUSIONS/SIGNIFICANCE: These observations suggest that the mechanical properties of the matrix environment play a significant role in regulating the proliferation and the morphological properties of cancer cells. Further, the multiwell format of the soft-plate assay is a useful and effective adjunct to established 3-dimensional cell culture models.

Differential requirement for focal adhesion kinase signaling in cancer progression in the transgenic adenocarcinoma of mouse prostate model.

Increasing evidence indicates that adhesion signaling plays an important role in the tumor microenvironment, contributing to cancer progression, invasion, and metastasis. Focal adhesion kinase (FAK) is a nonreceptor protein tyrosine kinase that regulates adhesion-dependent cell signaling and has been implicated in mediating steps in cancer progression and metastasis in many human cancers, including prostate. We have investigated the role of FAK in the appearance of adenocarcinoma (atypical epithelial hyperplasia of T antigen) and neuroendocrine carcinomas in the transgenic adenocarcinoma of mouse prostate (TRAMP) model using either Cre-mediated recombination to genetically ablate FAK expression or pharmacologic inhibition of FAK activity with the small-molecule inhibitor, PF-562,271. We provide evidence that loss of FAK or its inhibition with PF-562,271 does not alter the progression to adenocarcinoma. However, continued FAK expression (and activity) is essential for the androgen-independent formation of neuroendocrine carcinoma. These data indicate that integrin signaling through FAK is an important component of cancer progression in the TRAMP model and suggest that treatment modalities targeting FAK may be an appropriate strategy for patients with castrate-resistant cancer.

Vascular cell adhesion molecule-1 is a regulator of ovarian cancer peritoneal metastasis.

Ovarian cancers metastasize by attaching to and invading through the mesothelium, a single layer of mesothelial cells lining the peritoneal cavity. The presence of invasive peritoneal metastases is associated with a poor prognosis for ovarian cancer (5-year survival <25%). Vascular cell adhesion molecule-1 (VCAM-1) is a cell surface receptor that mediates leukocyte attachment and extravasation across endothelial and mesothelial monolayers at sites of inflammation. Membranous VCAM-1 expression was observed on the mesothelium of 13 of 14 women with ovarian cancer compared with 6 of 15 who were cancer-free. Using a cell culture model system of mesothelial invasion, highly tumorigenic SKOV-3 and ES-2 cells were 2.5 to 3 times more efficient in transmigration through the mesothelial monolayer compared with poorly tumorigenic OVCAR-3 cells. Blocking antibodies to, or small interfering RNA knockdown of, VCAM-1 or its ligand alpha(4)beta(1) integrin significantly decreased, but did not completely inhibit, transmigration of SKOV-3 cells through mesothelial monolayers. Furthermore, using a mouse model of ovarian cancer metastasis, treatment with VCAM-1 function-blocking antibodies decreased tumor burden and increased survival. Together, these observations implicate VCAM-1-alpha(4)beta(1) integrin interactions in the regulation of ovarian cancer cell mesothelial invasion and metastatic progression and offer the possibility of novel therapeutic targets.

Cellular characterization of a novel focal adhesion kinase inhibitor.

Focal adhesion kinase (FAK) is a member of a family of non-receptor protein-tyrosine kinases that regulates integrin and growth factor signaling pathways involved in cell migration, proliferation, and survival. FAK expression is increased in many cancers, including breast and prostate cancer. Here we describe perturbation of adhesion-mediated signaling with a FAK inhibitor, PF-573,228. In vitro, this compound inhibited purified recombinant catalytic fragment of FAK with an IC(50) of 4 nM. In cultured cells, PF-573,228 inhibited FAK phosphorylation on Tyr(397) with an IC(50) of 30-100 nM. Treatment of cells with concentrations of PF-573,228 that significantly decreased FAK Tyr(397) phosphorylation failed to inhibit cell growth or induce apoptosis. In contrast, treatment with PF-573,228 inhibited both chemotactic and haptotactic migration concomitant with the inhibition of focal adhesion turnover. These studies show that PF-573,228 serves as a useful tool to dissect the functions of FAK in integrin-dependent signaling pathways in normal and cancer cells and forms the basis for the generation of compounds amenable for preclinical and patient trials.