Amikar Sehdev

Epidermal Growth Factor Receptor Signaling Is Required for Microadenoma Formation in the Mouse Azoxymethane Model of Colonic Carcinogenesis

Colonic carcinogenesis involves the progressive dysregulation of homeostatic mechanisms that control growth. The epidermal growth factor (EGF) receptor (EGFR) regulates colonocyte growth and differentiation and is overexpressed in many human colon cancers. A requirement for EGFR in colonic premalignancy, however, has not been shown. In the current study, we used a specific EGFR antagonist, gefitinib, to investigate this role of the receptor in azoxymethane colonic premalignancy. The azoxymethane model shares many clinical, histologic, and molecular features of human colon cancer. Mice received azoxymethane i.p. (5 mg/kg/wk) or saline for 6 weeks. Animals were also gavaged with gefitinib (10 mg/kg body weight) or vehicle (DMSO) thrice weekly for 18 weeks, a dose schedule that inhibited normal receptor activation by exogenous EGF. Compared with control colonocytes [bromodeoxyuridine (BrdUrd), 2.2+/-1.2%], azoxymethane significantly increased proliferation (BrdUrd, 12.6+/-2.8%), whereas gefitinib inhibited this hyperproliferation (BrdUrd, 6.2+/-4.0%; <0.005). Azoxymethane significantly induced pro-transforming growth factor-alpha (6.4+/-1.3-fold) and increased phospho-(active) EGFR (5.9+/-1.1-fold), phospho-(active) ErbB2 (2.3+/-0.2-fold), and phospho-(active) extracellular signal-regulated kinase (3.3+/-0.4-fold) in premalignant colonocytes. Gefitinib inhibited activations of these kinases by >75% (P<0.05). Gefitinib also significantly reduced the number of large aberrant crypt foci and decreased the incidence of colonic microadenomas from 75% to 33% (P<0.05). Gefitinib concomitantly decreased cell cycle-regulating cyclin D1 and prostanoid biosynthetic enzyme cyclooxygenase-2 in microadenomas, suggesting that these regulators are key targets of EGFR in colonic carcinogenesis. These results show for the first time that EGFR signaling is required for early stages of colonic carcinogenesis. Our findings suggest, moreover, that inhibitors of EGFR might be useful in chemopreventive strategies in individuals at increased risk for colonic malignancies.

Epidermal Growth Factor Receptor Controls Flat Dysplastic Aberrant Crypt Foci Development and Colon Cancer Progression in the Rat Azoxymethane Model

Purpose: Colonic carcinogenesis deranges growth-regulating epidermal growth factor receptors (EGFR). We previously showed that EGFR signals were up-regulated in human aberrant crypt foci (ACF), putative colon cancer precursors. The azoxymethane model of colon cancer recapitulates many aspects of human colonic tumors. Recent studies indicate that flat dysplastic ACF with increased β-catenin are tumor precursors in this model. We asked, therefore, if EGFR signals are required for flat dysplastic ACF development and cancer progression. Experimental Design: Rats received azoxymethane or saline, and standard chow or chow supplemented with gefitinib, an EGFR inhibitor, for 44 weeks. EGFR signals were quantified in normal colon, flat ACF, and tumors by computerized analysis of immunostains and Western blots. K-ras mutations were assessed by PCR and mRNA for egfr ligands by quantitative real-time PCR. Results: EGFR inhibition with gefitinib decreased the incidence of flat dysplastic ACF from 66% to 36% and tumors from 71% to 22% (P < 0.05). This inhibitor also reduced the overexpressions of cyclin D1 and Cox-2 in flat ACF. Furthermore, in flat ACF, EGFR blockade decreased the up-regulation of c-Jun, FosB, phosphorylated active signal transducers and activators of transcription 3, and CCAAT/enhancer binding protein-β, potential regulators of cyclin D1 and Cox-2. In colonic tumors, EGFR blockade significantly decreased angiogenesis, proliferation, and progression while also increasing apoptosis (P < 0.05). Gefitinib also inhibited the activations of extracellular signal–regulated kinase, Src, and AKT pathways in tumors. Conclusions: We have shown for the first time that EGFR promotes the development of flat dysplastic ACF and the progression of malignant colonic tumors. Furthermore, we have mechanistically identified several transcription factors and their targets as EGFR effectors in colonic carcinogenesis.

Epidermal Growth Factor Receptor Is Required for Colonic Tumor Promotion by Dietary Fat in the Azoxymethane/Dextran Sulfate Sodium Model: Roles of Transforming Growth Factor-α and PTGS2

Purpose: Colon cancer is a major cause of cancer deaths. Dietary factors contribute substantially to the risk of this malignancy. Western-style diets promote development of azoxymethane-induced colon cancer. Although we showed that epidermal growth factor receptors (EGFR) controlled azoxymethane tumorigenesis in standard fat conditions, the role of EGFR in tumor promotion by high dietary fat has not been examined. Experimental Design: A/J C57BL6/J mice with wild-type Egfr (Egfrwt) or loss-of-function waved-2 Egfr (Egfrwa2) received azoxymethane followed by standard (5 fat) or western-style (20 fat) diet. As F1 mice were resistant to azoxymethane, we treated mice with azoxymethane followed by one cycle of inflammation-inducing dextran sulfate sodium to induce tumorigenesis. Mice were sacrificed 12 weeks after dextran sulfate sodium. Tumors were graded for histology and assessed for EGFR ligands and proto-oncogenes by immunostaining, Western blotting, and real-time PCR. Results:Egfrwt mice gained significantly more weight and had exaggerated insulin resistance compared with Egfrwa2 mice on high-fat diet. Dietary fat promoted tumor incidence (71.2 versus 36.7; P < 0.05) and cancer incidence (43.9 versus 16.7; P < 0.05) only in Egfrwt mice. The lipid-rich diet also significantly increased tumor and cancer multiplicity only in Egfrwt mice. In tumors, dietary fat and Egfrwt upregulated transforming growth factor-, amphiregulin, CTNNB1, MYC, and CCND1, whereas PTGS2 was only increased in Egfrwt mice and further upregulated by dietary fat. Notably, dietary fat increased transforming growth factor- in normal colon. Conclusions: EGFR is required for dietary fat-induced weight gain and tumor promotion. EGFR-dependent increases in receptor ligands and PTGS2 likely drive diet-related tumor promotion. (Clin Cancer Res 2009;15(22):67809)

Current management of gastrointestinal stromal tumors: Surgery, current biomarkers, mutations, and therapy

In the past decade, the addition of molecular diagnosis of mutations and use of tyrosine kinase inhibitors (TKIs), either as neoadjuvant/adjuvant therapy with surgery or as primary therapy in nonresectable gastrointestinal stromal tumors (GIST), has improved patient outcomes markedly. Additional therapeutics also are on the horizon. The goal of this review is to identify the current incidence, diagnostic modalities, and trends in personalizing the medical and operative management for patients with GIST. Medline, PubMed, and Google scholar were queried for recently published literature regarding new molecular mechanisms, targeted therapies, and clinical trials investigating the treatment of GIST. The objective of this review is to highlight the biomarkers under development, newly discovered mutations, and newer therapies targeting specific mutational phenotypes which are continually improving the outlook for patients with this disease.

Perioperative therapy for locally advanced gastroesophageal cancer: current controversies and consensus of care

Gastroesophageal cancer (GEC) remains a challenging problem in oncology. Anatomically, GEC is comprised of distal gastric adenocarcinoma (GC), classically associated with Helicobacter Pylori, while proximal esophagogastric adenocarcinoma (EGJ AC) has increased significantly in incidence over the past years. Despite contrasting etiologies, histologies, and molecular phenotypes of distal and proximal GEC, in many cases perioperative (and metastatic) treatment strategies converge to similar approaches. For patients undergoing curative intent surgery, advances in perioperative chemotherapy and/or chemoradiotherapy, either before and/or after surgery, have demonstrated improved survivals compared to surgery alone. This review focuses on how the ‘boundary’ of the Z-line and/or the anatomical distinction of ‘proximal’ (EGJ) vs. ‘distal’ (GC) cancer has led to diverse inclusion/exclusion criteria for clinical trial enrollment, embodying various combinations of chemotherapy and radiation before and/or after surgery. Supporting evidence of each of these approaches consequently has led to a number of varying practices by geographical region and Institution/Physician, based on differing experience, preference, and clinical circumstance. Adequate direct comparison of these approaches is lacking currently, but data from a number of concerted efforts should be available in the next years to further direct best standards of care. Introduction of biologically targeted agents, namely anti-angiogenics and anti-HER family therapeutics are being evaluated to determine whether further therapeutic gains can be realized over classic cytotoxic chemotherapy alone (with/without radiotherapy). To date, novel molecularly targeted agents have yet to demonstrate benefit in this setting. In the following comprehensive review we will address the intricacies of perioperative treatment of locally advanced GEC, with focus on clinical trials supporting the diverse set of perioperative multidisciplinary approaches.

Primary small cell carcinoma of the tonsil: a case report and review of the literature.

Small cell cancer (SCC) of the tonsil is a rare and aggressive cancer. There are only 10 cases of tonsillar SCC reported in the English literature. We present a case of tonsillar SCC successfully treated with induction chemotherapy using carboplatin and etoposide followed by concurrent chemoradiation therapy with cisplatin as radiosensitizer. The patient remained free of recurrence after 3 years of follow-up. We also provide a succinct review of all tonsillar SCC cases reported in the English literature and their outcomes.

A pharmacodynamic study of sirolimus and metformin in patients with advanced solid tumors

BackgroundSirolimus is a mammalian target of rapamycin (mTOR) inhibitor. Metformin may potentiate mTOR inhibition by sirolimus while mitigating its adverse effects. We conducted a pilot study to test this hypothesis.MethodsPatients with advanced solid tumor were treated with sirolimus for 7 days followed by randomization to either sirolimus with metformin (Arm A) or sirolimus (Arm B) until day 21. From day 22 onwards, all patients received sirolimus and metformin. The primary aim was to compare the change in phospho-p70S6K (pp70S6K) in peripheral blood mononuclear cells (PBMC) from day 8 to day 22 using a two-sample t test. Secondary aims were objective response rate, toxicity, and other serum pharmacodynamic biomarkers (e.g., fasting glucose, triglycerides, insulin, C-peptide, IGF-1, IGF-1R, IGF-BP, and leptin).Results24 patients were enrolled, with 18 evaluable for the primary endpoint. There was no significant difference in mean change in pp70S6K in arm A vs. arm B (− 0.12 vs. − 0.16; P = 0.64). Similarly, there were no significant differences in other serum pharmacodynamic biomarkers. There were no partial responses. There were no dose-limiting or unexpected toxicities.ConclusionsAdding metformin to sirolimus, although well tolerated, was not associated with significant changes in pp70S6K in PBMC or other serum pharmacodynamic biomarkers.ImpactCombining metformin with sirolimus did not improve mTOR inhibition.

Patterns of computed tomography surveillance in survivors of colorectal cancer at Veterans Health Administration facilities

Annual computed tomography (CT) scans are a component of the current standard of care for the posttreatment surveillance of survivors of colorectal cancer (CRC) after curative‐intent resection. The authors conducted a retrospective study with the primary aim of assessing patient, physician, and organizational characteristics associated with the receipt of CT surveillance among veterans.

Contribution of Chemotherapy to the Toxicity of Pelvic Irradiation

Pelvic malignancies encompass a diverse group of diseases and account for enormous morbidity and mortality worldwide. Given the established role of surgery and with better understanding of the potential synergy between chemotherapy and radiation, an era of combined modality therapy for these malignancies began to emerge in the 1990s. Many single institution and intergroup trials were conducted, establishing the role of combined modality therapy in pelvic malignancies by showing an improved survival, offering organ preservation and limiting surgical complications. However, these benefits accrued at the cost of increased acute toxicities as a result of the combined chemoradiation therapy. Interestingly, limited data suggest no significant increase in late/chronic toxicities, but ongoing and stringent follow-up will be critical to accurately define this issue which is of major interest to all cancer survivors. In the presence of limited data, it would be safe to assume that there is a higher rate of late toxicities given increased early effects lead to increased late effects and perhaps we would have seen these finding if the landmark chemoradiation trials would have collected data on late toxicities. In this chapter, we will review the currently existent literature on acute and late toxicities encountered by combining chemotherapy with radiation in the comprehensive therapy of pelvic malignancies.

Abstract A54: Possible targets of metformin in colorectal cancer

Background: Growing evidence suggests metformin improves survival in diabetic colorectal cancer (CRC) patients. However, the mechanism of action remains unclear. In order to explore the mechanistic relationship between metformin and colon cancer, we examined the expression levels of several proteins implicated in metformin9s action. Methods: We collected clinical-pathological and outcomes data on all CRC patients treated at the University of Chicago (UC) from 2006-2010. The data was collected through UC cancer registry and chart review. Diabetic CRC patients and matched controls (matched on race and stage) were selected for immunostaining (IHC). Tissues blocks (FFPE) were retrieved and tissue microarray (TMA) were constructed. IHC was performed for pAMPK, pmTOR, p70S6K, 4E-BP1, pAKT, IGF1R, beta-Catenin and Ki-67. Total score was calculated from the intensity and percentage scoring. The results were analyzed in two groups: diabetic CRC patients on metformin (group 1) and diabetic or non-diabetic CRC patients not on metformin (group 2). Chi-square test was done for estimating statistical significance between groups keeping a level of significance at 10% (alpha Results: The mean age of CRC patients was 62.7 years, 49% were males. Out of a total of 700 patients, 79 (11.21%) were diabetic. Metformin was prescribed to 40.5% of diabetic patients. Only 52 diabetics have FFPE block available so TMA was constructed with 104 patients in total (52 cases and 52 controls). Immunostaining was analyzable for a total of 84 patients. There were 18 and 66 patients in group 1 and 2, respectively. We found a lower expression of Ki-67 in the metformin group (group 1; 39%) as compared to non-metformin group (group 2; 64%) which was statistically significant (p = 0.04). IGF1R and beta-Catenin showed a higher expression in non-metformin group (89% and 95%, respectively) as compared to metformin group (72% and 83%, respectively) which was close to significance (p=0.12 and p=0.13, respectively). There was no significant difference between the expression of pAMPK, pmTOR, p70S6K, 4E-BP1 and pAKT in the two groups. Conclusions: Metformin appears to improve the survival of CRC patients by decreasing proliferation. The results need to be validated in a larger study. Citation Format: Amikar Sehdev, Galina Khramtsova, Nora Joseph, Blase P. Polite, Marc B. Bissonnette, Olopade I. Olufunmilayo. Possible targets of metformin in colorectal cancer. [abstract]. In: Proceedings of the Thirteenth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2014 Sep 27-Oct 1; New Orleans, LA. Philadelphia (PA): AACR; Can Prev Res 2015;8(10 Suppl): Abstract nr A54.