Pippa Newell

Pivotal Role of mTOR Signaling in Hepatocellular Carcinoma

BACKGROUND & AIMS The advent of targeted therapies in hepatocellular carcinoma (HCC) has underscored the importance of pathway characterization to identify novel molecular targets for treatment. We evaluated mTOR signaling in human HCC, as well as the antitumoral effect of a dual-level blockade of the mTOR pathway. METHODS The mTOR pathway was assessed using integrated data from mutation analysis (direct sequencing), DNA copy number changes (SNP-array), messenger RNA levels (quantitative reverse-transcription polymerase chain reaction and gene expression microarray), and protein activation (immunostaining) in 351 human samples [HCC (n = 314) and nontumoral tissue (n = 37)]. Effects of dual blockade of mTOR signaling using a rapamycin analogue (everolimus) and an epidermal/vascular endothelial growth factor receptor inhibitor (AEE788) were evaluated in liver cancer cell lines and in a xenograft model. RESULTS Aberrant mTOR signaling (p-RPS6) was present in half of the cases, associated with insulin-like growth factor pathway activation, epidermal growth factor up-regulation, and PTEN dysregulation. PTEN and PI3KCA-B mutations were rare events. Chromosomal gains in RICTOR (25% of patients) and positive p-RPS6 staining correlated with recurrence. RICTOR-specific siRNA down-regulation reduced tumor cell viability in vitro. Blockage of mTOR signaling with everolimus in vitro and in a xenograft model decelerated tumor growth and increased survival. This effect was enhanced in vivo after epidermal growth factor blockade. CONCLUSIONS MTOR signaling has a critical role in the pathogenesis of HCC, with evidence for the role of RICTOR in hepato-oncogenesis. MTOR blockade with everolimus is effective in vivo. These findings establish a rationale for targeting the mTOR pathway in clinical trials in HCC.

Ras pathway activation in hepatocellular carcinoma and anti-tumoral effect of combined sorafenib and rapamycin in vivo ☆

BACKGROUND/AIMS The success of sorafenib in the treatment of advanced hepatocellular carcinoma (HCC) has focused interest on the role of Ras signaling in this malignancy. We investigated the molecular alterations of the Ras pathway in HCC and the antineoplastic effects of sorafenib in combination with rapamycin, an inhibitor of mTOR pathway, in experimental models. METHODS Gene expression (qRT-PCR, oligonucleotide microarray), DNA copy number changes (SNP-array), methylation of tumor suppressor genes (methylation-specific PCR) and protein activation (immunohistochemistry) were analysed in 351 samples. Anti-tumoral effects of combined therapy targeting the Ras and mTOR pathways were evaluated in cell lines and HCC xenografts. RESULTS Different mechanisms accounted for Ras pathway activation in HCC. H-ras was up-regulated during different steps of hepatocarcinogenesis. B-raf was overexpressed in advanced tumors and its expression was associated with genomic amplification. Partial methylation of RASSF1A and NORE1A was detected in 89% and 44% of tumors respectively, and complete methylation was found in 11 and 4% of HCCs. Activation of the pathway (pERK immunostaining) was identified in 10.3% of HCC. Blockade of Ras and mTOR pathways with sorafenib and rapamycin reduced cell proliferation and induced apoptosis in cell lines. In vivo, the combination of both compounds enhanced tumor necrosis and ulceration when compared with sorafenib alone. CONCLUSIONS Ras activation results from several molecular alterations, such as methylation of tumor suppressors and amplification of oncogenes (B-raf). Sorafenib blocks signaling and synergizes with rapamycin in vivo, preventing tumor progression. These data provide the rationale for testing this combination in clinical studies.

Expression of NF-κB p50 in Tumor Stroma Limits the Control of Tumors by Radiation Therapy

Radiation therapy aims to kill cancer cells with a minimum of normal tissue toxicity. Dying cancer cells have been proposed to be a source of tumor antigens and may release endogenous immune adjuvants into the tumor environment. For these reasons, radiation therapy may be an effective modality to initiate new anti-tumor adaptive immune responses that can target residual disease and distant metastases. However, tumors engender an environment dominated by M2 differentiated tumor macrophages that support tumor invasion, metastases and escape from immune control. In this study, we demonstrate that following radiation therapy of tumors in mice, there is an influx of tumor macrophages that ultimately polarize towards immune suppression. We demonstrate using in vitro models that this polarization is mediated by transcriptional regulation by NFκB p50, and that in mice lacking NFκB p50, radiation therapy is more effective. We propose that despite the opportunity for increased antigen-specific adaptive immune responses, the intrinsic processes of repair following radiation therapy may limit the ability to control residual disease.

Optimizing Timing of Immunotherapy Improves Control of Tumors by Hypofractionated Radiation Therapy

The anecdotal reports of promising results seen with immunotherapy and radiation in advanced malignancies have prompted several trials combining immunotherapy and radiation. However, the ideal timing of immunotherapy with radiation has not been clarified. Tumor bearing mice were treated with 20Gy radiation delivered only to the tumor combined with either anti-CTLA4 antibody or anti-OX40 agonist antibody. Immunotherapy was delivered at a single timepoint around radiation. Surprisingly, the optimal timing of these therapies varied. Anti-CTLA4 was most effective when given prior to radiation therapy, in part due to regulatory T cell depletion. Administration of anti-OX40 agonist antibody was optimal when delivered one day following radiation during the post-radiation window of increased antigen presentation. Combination treatment of anti-CTLA4, radiation, and anti-OX40 using the ideal timing in a transplanted spontaneous mammary tumor model demonstrated tumor cures. These data demonstrate that the combination of immunotherapy and radiation results in improved therapeutic efficacy, and that the ideal timing of administration with radiation is dependent on the mechanism of action of the immunotherapy utilized.

VEGF Signaling in Cancer Treatment

Induction of angiogenesis represents one of the major hallmarks of cancer. The growth of new vessels is crucial to provide malignant cells with an adequate supply of oxygen and nutrients. It is generally accepted that vascular endothelial growth factor (VEGF) is a major driver of the angiogenic process in physiological and pathological processes in both embryo and adult. VEGF is often found overexpressed in tumors, as well as its receptors VEGFR1 and VEGFR2. Hence, several different strategies have been designed to target VEGF signal transduction. In the last decades, multiple inhibitors have been therapeutically validated in preclinical models and several clinical trials. Neutralizing monoclonal antibodies against VEGF and small molecule tyrosine kinase inhibitors targeting VEGFRs have been shown to block its angiogenic activity, resulting in tumor vascular regression, anti-tumor effects and improvements in patient survival. However, side effects and lack of efficacy in some instances challenge the potential clinical impact of these therapies. This review examines the role of VEGF signaling in cancer and outlines the current status of anti-angiogenic therapies against VEGF pathway.

β-Catenin signaling in hepatocellular cancer: Implications in inflammation, fibrosis, and proliferation

β-Catenin signaling is implicated in hepatocellular carcinoma (HCC), although its role in inflammation, fibrosis, and proliferation is unclear. Commercially available HCC tissue microarray (TMA) of 89 cases was assessed for β-catenin, one of its transcriptional targets glutamine synthetase (GS), proliferation (PCNA), inflammation (CD45), and fibrosis (Sirius Red). HCC cells transfected with wild-type (WT) or mutant-β-catenin were evaluated for β-catenin-T cell factor transactivation by TOPFlash reporter activity and expression of certain targets. Hepatocyte-specific-serine-45-mutated β-catenin transgenic mice (TG) and controls (Con) were used to study thioacetamide (TAA)-induced hepatic fibrosis and tumorigenesis. Sustained β-catenin activation was only observed in mutant-, not WT-β-catenin transfected HCC cells. Aberrant intratumoral β-catenin stabilization was evident in 33% cases with 9% showing predominant nuclear with some cytoplasmic (N/C) localization and 24% displaying predominant cytoplasmic with occasional nuclear (C/N) localization. N/C β-catenin was associated with reduced fibrosis (p=0.017) and tumor-wide GS staining (p<0.001) while C/N correlated with increased intratumoral inflammation (p=0.064) and proliferation (p=0.029). A small subset of HCC patients (15.5%) lacked β-catenin staining and exhibited low inflammation and fibrosis (p<0.05). TG and Con mice exposed to TAA showed comparable development of fibrosis and progression to cirrhosis and HCC. Taken together the data suggests a complex relationship of β-catenin, inflammation, fibrosis and HCC. GS staining is highly sensitive in identifying HCC with nuclear β-catenin, which may in turn represent β-catenin mutations, and does so with high negative predictive value. Also, β-catenin mutations and cirrhosis do not appear to cooperate in HCC pathogenesis in mice and men.

Molecular targeted therapies in hepatocellular carcinoma: From pre-clinical models to clinical trials

Hepatocellular carcinoma (HCC) is one of the world’s most common and deadly cancers. Less than one-third of patients can currently benefit from potentially curative therapies in the West [1]. However, a new era has dawned in oncology with novel and promising drugs emerging in parallel with a better understanding of the pathogenesis of cancer [2]. The advent of sorafenib – a multikinase inhibitor – as an effective therapy in advanced HCC has enhanced the interest in testing new molecular therapies in experimental and clinical studies [3]. Integrative genomic studies in human HCC samples have begun to identify subgroups of patients with characteristic molecular features such as mutations, gene expression profiles and chromosomal aberrations [4,5]. These studies have underlined the fact that a number of molecular pathways are disrupted in almost all tumors, involving critical functions for the progression or dissemination of the disease. Such is the case of three main cellular functions: (1) Activation of pro-angiogenic signals mediated by VEGF, PDGER,

The Peripheral Myeloid Expansion Driven by Murine Cancer Progression Is Reversed by Radiation Therapy of the Tumor

Expansion of myeloid-lineage leukocytes in tumor-bearing mice has been proposed as a cause of systemic immunosuppression. We demonstrate that radiation therapy of tumors leads to a decline in myeloid cell numbers in the blood and a decrease in spleen size. The frequency of myeloid cells does not decline to the level seen in tumor-free mice: we demonstrate that metastatic disease can prevent myeloid cell numbers from returning to baseline, and that tumor recurrence from residual disease correlates with re-expansion of myeloid lineage cells. Radiation therapy results in increased proliferation of T cells in the spleen and while T cell responses to foreign antigens are not altered by tumor burden or myeloid cell expansion, responses to tumor-associated antigens are increased after radiation therapy. These data demonstrate that myeloid cell numbers are directly linked to primary tumor burden, that this population contracts following radiation therapy, and that radiation therapy may open a therapeutic window for immunotherapy of residual disease.

Umbilical Hernia Repair in Patients With Signs of Portal Hypertension: Surgical Outcome and Predictors of Mortality

OBJECTIVES To compare the outcomes of umbilical hernia repair in patients with and without signs of portal hypertension, such as esophageal varices or ascites; to assess the effect of emergency surgery on complication rates; and to identify predictors of postoperative mortality. DESIGN Database search from January 1, 2005, through December 31, 2009. SETTING North American hospitals participating in the American College of Surgeons National Surgical Quality Improvement Program initiative. PATIENTS We studied patients who underwent umbilical hernia repair. Those with congestive heart failure, disseminated malignant tumor, or chronic renal failure while undergoing dialysis were excluded. MAIN OUTCOME MEASURES Preoperative variables and perioperative course were analyzed. Main outcome measures were morbidity and mortality after umbilical hernia repair. RESULTS A total of 390 patients with ascites and/or esophageal varices formed the study group, and the remaining 22 952 patients formed the control group. The overall morbidity and mortality rates for the study group were 13.1% and 5.1%, whereas these rates were 3.9% and 0.1% for the control group, respectively (P < .001). For the study group, the mortality after elective repair among patients with a model for end-stage liver disease (MELD) score greater than 15 was 11.1% compared with 1.3% in patients with a MELD score of 15 or less. The patients with ascites and/or esophageal varices underwent emergency surgery more frequently than the control group (37.7% vs 4.9%; P < .001). Emergency surgery for the study group was associated with a higher morbidity than elective surgery (20.8% vs 8.3%; P < .001) but not a significantly higher mortality (7.4% vs 3.7%; P = .11). However, logistic regression analysis showed that age older than 65 years, MELD score higher than 15, albumin level less than 3.0 g/dL (to convert to grams per liter, multiply by 10), and sepsis at presentation were more predictive of postoperative mortality. CONCLUSIONS Umbilical hernia repair in the presence of ascites and/or esophageal varices is associated with significant postoperative complication rates. Emergency surgery is associated with higher morbidity rates but not significantly higher mortality rates. Elective repair of umbilical hernia should be avoided for those with adverse predictors, such as age older than 65 years, MELD score higher than 15, and albumin level less than 3.0 g/dL.

Expression of Arginase I in Myeloid Cells Limits Control of Residual Disease after Radiation Therapy of Tumors in Mice

An accumulating body of evidence demonstrates that radiation therapy can generate adaptive immune responses that contribute to tumor control. However, in the absence of additional immune therapy, the adaptive immune response is insufficient to prevent tumor recurrence or affect distant disease. It has been shown in multiple models that tumor-infiltrating myeloid cells exhibit alternative activation phenotypes and are able to suppress adaptive immune responses, and recent data suggests that the myeloid response in tumors treated with cytotoxic therapy limits tumor control. We hypothesized that tumor myeloid cells inhibit the adaptive immune response after radiation therapy through expression of the enzyme arginase I. Using a myeloid cell-specific deletion of arginase I in mice, we demonstrate an improved tumor control after radiation therapy. However, tumors still recurred despite the conditional knockdown of arginase I. Since multiple alternative factors may combine to inhibit adaptive immunity, we propose that targeting macrophage differentiation may be a more effective strategy than targeting individual suppressive pathways.