Amit Mahipal

Importins and exportins as therapeutic targets in cancer.

The nuclear transport proteins, importins and exportins (karyopherin-β proteins), may play an important role in cancer by transporting key mediators of oncogenesis across the nuclear membrane in cancer cells. During nucleocytoplasmic transport of tumor suppressor proteins and cell cycle regulators during the processing of these proteins, aberrant cellular growth signaling and inactivation of apoptosis can occur, both critical to growth and development of tumors. Karyopherin-β proteins bind to these cargo proteins and RanGTP for active transport across the nuclear membrane through the nuclear pore complex. Importins and exportins are overexpressed in multiple tumors including melanoma, pancreatic, breast, colon, gastric, prostate, esophageal, lung cancer, and lymphomas. Furthermore, some of the karyopherin-β proteins such as exportin-1 have been implicated in drug resistance in cancer. Importin and exportin inhibitors are being considered as therapeutic targets against cancer and have shown preclinical anticancer activity. Moreover, synergistic activity has been observed with various chemotherapeutic and targeted agents. However, clinical development of the exportin-1 inhibitor leptomycin B was stopped due to adverse events, including vomiting, anorexia, and dehydration. Selinexor, a selective nuclear export inhibitor, is being tested in multiple clinical trials both as a single agent and in combination with chemotherapy. Selinexor has demonstrated clinical activity in multiple cancers, especially acute myelogenous leukemia and multiple myeloma. The roles of other importin and exportin inhibitors still need to be investigated clinically. Targeting the key mediators of nucleocytoplasmic transport in cancer cells represents a novel strategy in cancer intervention with the potential to significantly affect outcomes.

Role of Biologics in First-Line Treatment of Colorectal Cancer

In the past decade, significant advances have been made in the treatment of advanced colorectal cancer. Multiple cytotoxic agents and targeted therapies have been approved for management of metastatic colorectal cancer, leading to improvement of median overall survival in clinical trials to more than 30 months. Of note, before the introduction of biologics into treatment algorithms for metastatic colorectal cancer, median survival in phase III trials never exceeded 24 months. In 2016, the most common treatment approach in first line is a combination of chemotherapy with a biologic agent. The choice of therapy is influenced by patient factors (eg, age, comorbidities), tumor characteristics (eg, overall tumor burden, pattern of metastatic spread, mutation signature), potential adverse effects of therapy, and goals of treatment. The choice between irinotecan- or oxaliplatin-based cytotoxic chemotherapy regimen is primarily based on differential toxicity profile because they have similar efficacy. Currently, three biologic agents-bevacizumab, cetuximab, and panitumumab-are approved for first-line treatment of metastatic colorectal cancer. For patients with mutant RAS and likely mutant BRAF V600E tumors, bevacizumab is the only biologic agent that can be used in conjunction with cytotoxic chemotherapy. The choice of anti-epidermal growth factor antibody or anti-vascular endothelial growth factor antibody in RAS wild-type tumors is based on the specific clinical scenario. Recently, some clinical and molecular biomarkers have emerged that may help in decision making. In this review, we discuss the role of biologics in the management of first-line treatment of metastatic colorectal cancer.

Contemporary Management of Localized Resectable Pancreatic Cancer

Pancreatic cancer is the third most common cause of cancer deaths in the United States. Surgical resection with negative margins still constitutes the cornerstone of potentially curative therapy, but is possible only in 15–20% of patients at the time of initial diagnosis. Accumulating evidence suggests that the neoadjuvant approach may improve R0 resection rate in localized resectable and borderline resectable diseases, and potentially downstage locally advanced disease to achieve surgical resection, though the impact on survival is to be determined. Despite advancements in the last decade in developing effective combinational chemo-radio therapeutic options, preoperative treatment strategies, and better peri-operative care, pancreatic cancer continues to carry a dismal prognosis in the majority. Prodigious efforts are currently being made in optimizing the neoadjuvant therapy with a better toxicity profile, developing novel agents, imaging techniques, and identification of biomarkers for the disease. Advancement in our understanding of the tumor microenvironment and molecular pathology is urgently needed to facilitate the development of novel targeted and immunotherapies for this setting. In this review, we detail the current literature on contemporary management of resectable, borderline resectable and locally advanced pancreatic cancer with a focus on future directions in the field.

Novel targeted treatment options for advanced cholangiocarcinoma

ABSTRACT Introduction: Surgical resection remains the mainstay of potentially curative treatment in the early stages of cholangiocarcinoma, whereas for the advanced stage, systemic chemotherapeutics and experimental targeted therapies are the primary treatment options. The molecular heterogeneity of the tumor is based on location, liver dysfunction, and relative rarity of the disease and confers challenges for clinical trial enrollment. The advancements in the understanding of molecular pathogenesis of cholangiocarcinoma have led to the development of targeted therapies that are currently being evaluated in the clinical trials. Areas covered: This review summarizes the current understanding and future directions of targeted therapeutic options in the management of advanced cholangiocarcinoma. Expert opinion: Advanced cholangiocarcinoma has a dismal prognosis; improved understanding of the molecular pathogenesis and advancements in development of targeted therapy offers hope that we may improve outcomes in this rare, but highly lethal cancer. Among the newly discovered molecular alterations, targeting FGFR2 fusions, IDH1/2 mutations and HER2 receptors hold great promise for improving the future management of cholangiocarcinoma. Immunotherapy in combination with targeted agents and chemotherapy may improve outcomes. In addition, drugs targeting the MEK, EGFR, KRAS, BRAF, and ROS1 pathways and neo-angiogenesis may also provide new horizons in the management of cholangiocarcinoma.

Malignant transformation of biliary adenofibroma: a rare biliary cystic tumor

Biliary adenofibromas (BAFs) are rare, benign biliary cystic tumors with potential for malignant transformation. Of the eleven prior cases of BAF reported in the literature, six showed evidence of malignant transformation. We describe the clinical, imaging and pathology features of two cases of malignant BAF and review the existing literature to raise awareness of this entity and provide additional tools for diagnosing this rare tumor Additionally, we identified a loss of function mutation in the cyclin-dependent kinase inhibitor 2A (CDKN2A) tumor suppressor gene in a malignant caudate lobe BAF, thereby providing potential insight into the molecular pathogenesis of BAF malignant transformation. Although additional cases and longer-term follow-up are needed, our cases suggest that recurrence or metastasis of malignant BAF is not common and that complete surgical resection can be curative.

A Phase I study to evaluate the safety and antitumor activity of durvalumab (MEDI4736) in combination with tremelimumab in patients with advanced solid tumors

Meeting abstracts The immune system is able to control the growth of many types of cancers. Most tumors show infiltration by tumor infiltrating lymphocytes, but tumors modulate the local microenvironment by expressing immune-inhibitory molecules. Blockade of immune checkpoints such as cytotoxic T-

Staging and Prognostic Implications

Pancreatic cancer is the fourth most common cause of cancer deaths in the United States and is associated with very poor prognosis. Surgery remains the mainstay curative approach, but only one-fifth of the patients after pancreatic resection are alive at 5 years. Two different staging systems have been developed that help in determining prognosis and therapeutic strategy. TNM staging proposed by the American Joint Committee on Cancer (AJCC) divides patients in stages I–IV. The prognostic implications of TNM staging have been validated in large series. Clinical classification system based on imaging studies is utilized for making treatment decisions in patients with pancreatic cancer. Patients are classified into four groups: resectable, borderline resectable, locally advanced, and metastatic. The key differentiation in this staging system is the involvement of vascular structure that has implications for surgical interventions and clinical outcomes. Varied definitions from different medical societies are utilized for classifying patients into clinical groups. Recently, there has been attempt to standardize the definition of resectable, borderline resectable, and locally advanced pancreatic cancer. Imaging modalities including endoscopic ultrasound, computed tomography, magnetic resonance imaging, and positron-emission tomography are utilized for accurate staging. Diagnostic laparoscopy is incorporated in selected centers as part of preoperative staging.

Rho GTPase effectors and NAD metabolism in cancer immune suppression

ABSTRACT Introduction: Sustained proliferative signaling and de-regulated cellular bioenergetics are two of the chief hallmarks of cancer. Alterations in the Ras pathway and its downstream effectors are among the major drivers for uncontrolled cell growth in many cancers. The GTPases are one of the signaling molecules that activate crucial signal transducing pathways downstream of Ras through several effector proteins. The GTPases (GTP bound) interact with several effectors and modulate a number of different biological pathways including those that regulate cytoskeleton, cellular motility, cytokinesis, proliferation, apoptosis, transcription and nuclear signaling. Similarly, the altered glycolytic pathway, the so-called ‘Warburg effect’, rewires tumor cell metabolism to support the biosynthetic requirements of uncontrolled proliferation. There exists strong evidence for the critical role of the glycolytic pathway’s rate limiting enzymes in promoting immunosuppression. Areas covered: We review the emerging roles of GTPase effector proteins particularly the p21 activated kinase 4 (PAK4) and nicotinamide biosynthetic pathway enzyme nicotinamide phosphoribosyltransferase (NAMPT) as signaling molecules in immune surveillance and the immune response. Expert opinion: In this expert opinion article we highlight the recent information on the role of GTPases and the metabolic enzymes on the immune microenvironment and propose some unique immune therapeutic opportunities.