Prediction of survival in stage iv colorectal cancer by a computed tomographic scoring system for hepatic metastasis

ASSOCIATION FOR ACADEMIC SURGERY—ABSTRACTS D. W. McFadden, M.D. West Virginia University Department of Surgery, Morgantown, WV. Introduction: Obesity is associated with an increased risk of developing cancer. Leptin is a 16 kD peptide hormone secreted by adipose tissue with higher circulating concentrations reported in obese people. In addition, recent studies indicate that leptin is mitogenic, as well as pro-angiogenic, in reproductive tissues. We have demonstrated that exogenous leptin leads to increased proliferation of breast and prostate cancer cells in vitro. However, the mechanism behind this effect is unknown. We hypothesized that increased cancer cell proliferation in response to leptin occurs via alterations in mitogen-activated protein kinase (MAPK) and phosphatidylinositol-3 kinase (PI3K) signal transduction pathways. Methods: Two cancer cell lines, ZR-75 (breast) and DU145 (prostate), were cultured using standard techniques. Cells were treated with human recombinant leptin (40 ng/ml) for 48 h. This dose of leptin simulates circulating levels in obese humans. After treatment, cells were harvested and analyzed via immunoblot for Akt and ERK phosphorylation, measures of PI3K and MAPK activity respectively. Results: Western blot analysis revealed that PI3K activity was not altered by leptin stimulation in either cell line tested. However, after treatment, ERK phosphorylation was increased in both the ZR-75 (approximately 4-fold) and DU145 (approximately 2-fold) cell lines, indicating an angiogenic response to leptin exposure. Conclusions: These preliminary results indicate that MAPK activation may play an important role in leptin-induced cancer cell proliferation. Moreover, it suggests that high levels of circulating leptin could act in vivo as a growth factor in the progression of breast and prostate cancers, thus establishing a link between the risk of obesity and carcinogenesis. P90. Poster withdrawn at author’s request. P91. Prediction of Survival in Stage Iv Colorectal Cancer by a Computed Tomographic Scoring System for Hepatic Metastasis. M. R. Dixon, M.D., J. S. Haukoos, M.D., S. M. Udani, J. J. Naghi, T. D. Arnell, M.D., R. Sinow, M.D., M. J. Stamos, M.D. Harbor-UCLA Medical Center Department of Surgery, Torrance, CA. To assess the relation between the burden of hepatic metastasis on initial CT scan and survival. A simple scoring system to quantify the degree of hepatic involvement was utilized by a single staff radiologist who retrospectively reviewed the CT scans obtained on admission of 48 patients who presented to the study institution with stage IV colon and rectal cancer between 1991 and 1998. The radiologist was blinded to the clinical presentation and survival of the patients. The scoring system separated patients into five groups depending on the radiologist’s visual calculation of the hepatic involvement by metastatic disease: 0% (stratum 1), 1–25% (stratum 2), 25–50% (stratum 3), 50 –75% (stratum 4) and more than 75% (stratum 5). (Patients with 0% hepatic involvement had known metastatic disease at another site.) The results of this scoring system were then correlated with survival data. KaplanMeier curves demonstrated a statistically significant difference in survival between the different groups (p ⫽ 0.02). During the first four months after presentation, 91% (95% CI: 59%–100%) of patients in stratum 1 survived and 87% (95% CI: 60 –98%) of patients in stratum 2 survived, while only 43% (95%:CI 10 – 82%), 40% (95% CI: 10 – 82%) and 22% (95% CI: 3– 60%) of patients in Strata 3, 4 and 5 survived, respectively. Kruskal-Wallis testing also showed a significant difference across the five groups (p ⫽ 0.007). Strata 1 and 2, with lower hepatic tumor burdens, showed longer survival times with median survival of 312 days [IQR:143– 739] and 293 days [IQR: 225–706]. As the amount of hepatic involvement increased, the median survival decreased with strata 3, 4, and 5 demonstrating a progressive decrease in survival time with median values of 100 days [IQR:38 –375], 54 days [IQR:43– 139] and 22 days [IQR:11–56], respectively. We have developed a

301

simple anatomical CT-based scoring system which significantly correlates with survival of stage IV colorectal cancer patients. Most clinically important, a significant difference in survival was seen in the first few months after presentation. Assessing the volume of hepatic involvement is a useful adjunct to the clinician in providing optimal care to patients with advanced colon and rectal cancer. P92. CD28 Is Not Required for B7-Mediated Costimulation of Nk Cell Proliferation in Response to Tumor Challenge. E. Kocak, M.D., S. F. Abdessalam, M.D., K. May, E. W. Martin, Y. Liu, Ph.D. The Ohio State University Hospitals. Introduction: Preliminary data have shown that two signals, both MHC class I and the costimulatory molecule B7-1, are required for NK cell-mediated rejection of allogeneic tumors and for activation of NK cells in vivo. In view of the fact that B7-1 and B7-2 interact with the receptor CD28 on T cells, this study investigates the role of CD28 in B7-mediated proliferation of NK cells. Methods: C57BL/6 mice deficient for RAG-1 or both RAG-1 and CD28 were injected intravenously with either 10 6 B7-expressing plasmacytoma cells (J558-B7) or B7-deficient plasmacytoma cells (J558-Neo) followed by intraperitoneal injections of bromodeoxyuridine (BrdU) every 12 hours. Mice were sacrificed 48 hours after tumor cell challenge for analysis. Mononuclear leukocytes from the spleen were stained with NK cell surface markers, and intracellularly with anti-BrdU mAb or isotype control. Cells were then analyzed by flow cytometry. There were twelve mice per experiment. Similar methods were employed to compare NK cell proliferation in C57BL/6 wild type versus C57BL/6 mice deficient only for CD28. Results: Consistent with previous studies, in RAG-1 deficient mice, there was a significantly increased proliferation of NK cells in response to B7-expressing tumor cell challenge compared to non-B7 expressing tumor (5.7% vs 12.3%). In RAG-1 knockout mice challenged with B7-expressing tumors, the proliferation of NK cells was increased in the absence of CD28 (12.3% vs 17.4%). This contradicts the result that would be expected if B7/CD28 interaction had played a role in B7-mediated proliferation. Similarly, in C57BL/6 wild type mice compared with C56BL/6 mice deficient for CD28, the proliferation of NK cells was not significantly different (14.2% vs 13.8%), further supporting that the B7/CD28 interaction does not play a role in proliferation. Conclusion: These findings indicate that CD28 is not required for B7-mediated costimulation of NK cell proliferation in response to tumor challenge. Future studies will investigate the potential role of alternative B7 family receptors, such as CTLA-4, in NK cell costimulation. P93. p53 Status Determines IRF-1 Induction of p21 and Growth Inhibition in HCT116 Colon Cancer Cells. M. Armstrong, M. T. Stang, M.D., Y. Liu, M.D., P. Yan, M.D., S. E. Carty, M.D., J. H. Yim, M.D. University of Pittsburgh. IRF-1 is a tumor suppressor which appears to have greater growth inhibition in cancer cells versus non-malignant cells; we hypothesize that cancer cells which have mutant or absent p53 are inhibited more by IRF-1 than non-malignant cells that have wildtype p53. Methods: HCT116 human colon cancer cells with wildtype p53 (p53 wt) and HCT116 cells in which p53 was deleted in both alleles (p53 ko) were used. Cells were treated for 4h with recombinant adenovirus expressing IRF-1 (Ad-IRF-1), empty adenoviral vector (␺5), or mock, and media changed. Cells were harvested at 24h for western blot for IRF-1, p21, and ␤-actin, and assessed for growth inhibition at 72h by CellTiter-glo assay. Growth inhibition data is reported as % growth inhibition ⫾ SEM of each treatment compared to mock treatment. Results: AdIRF-1 at 100 MOI produced equivalent or more IRF-1 in the p53 wt cell line versus the p53 ko cell line (Fig. B), but demonstrated