RAV12 Accelerates the Desensitization of Akt/PKB Pathway of Insulin-like Growth Factor I Receptor Signaling in COLO205

A topography of immunotherapies against gastrointestinal malignancies

Gastrointestinal (GI) cancers are one of the leading causes of death worldwide. Although various approaches are implemented to improve the health condition of GI patients, none of the treatment protocols promise for eradicating cancer. However, a treatment mechanism against any kind of disease condition is already existing executing inside the human body. The 'immune system' is highly efficient to detect and destroy the unfavourable events of the body including tumor cells. The immune system can restrict the growth and proliferation of cancer. Cancer cells behave much smarter and adopt new mechanisms for hiding from the immune cells. Thus, cancer immunotherapy might play a decisive role to train the immune system against cancer. In this review, we have discussed the immunotherapy permitted for the treatment of GI cancers. We have discussed various methods and mechanisms, periodic development of cancer immunotherapies, approved biologicals, completed and ongoing clinical trials, role of various biopharmaceuticals, and epigenetic factors involved in GI cancer immunotherapies (graphical abstract Figure 1).

Calcium homeostasis and ER stress in control of autophagy in cancer cells

Autophagy is a basic catabolic process, serving as an internal engine during responses to various cellular stresses. As regards cancer, autophagy may play a tumor suppressive role by preserving cellular integrity during tumor development and by possible contribution to cell death. However, autophagy may also exert oncogenic effects by promoting tumor cell survival and preventing cell death, for example, upon anticancer treatment. The major factors influencing autophagy are Ca²⁺ homeostasis perturbation and starvation. Several Ca²⁺ channels like voltage-gated T- and L-type channels, IP3 receptors, or CRAC are involved in autophagy regulation. Glucose transporters, mainly from GLUT family, which are often upregulated in cancer, are also prominent targets for autophagy induction. Signals from both Ca²⁺ perturbations and glucose transport blockage might be integrated at UPR and ER stress activation. Molecular pathways such as IRE 1-JNK-Bcl-2, PERK-eIF2α-ATF4, or ATF6-XBP 1-ATG are related to autophagy induced through ER stress. Moreover ER molecular chaperones such as GRP78/BiP and transcription factors like CHOP participate in regulation of ER stress-mediated autophagy. Autophagy modulation might be promising in anticancer therapies; however, it is a context-dependent matter whether inhibition or activation of autophagy leads to tumor cell death.

The brain tumor microenvironment

High-grade brain tumors are heterogeneous with respect to the composition of bona fide tumor cells and with respect to a range of intermingling parenchymal cells. Glioblastomas harbor multiple cell types, some with increased tumorigenicity and stem cell-like capacity. The stem-like cells maybe the cells of origin for tumor relapse. However, the tumor-associated parenchymal cells such as vascular cells,microglia, peripheral immune cells, and neural precursor cells also play a vital role in controlling the course of pathology.In this review, we describe the multiple interactions of bulk glioma cells and glioma stem cells with parenchymal cell populations and highlight the pathological impact as well as signaling pathways known for these types of cell-cell communication. The tumor-vasculature not only nourishes glioblastomas, but also provides a specialized niche for these stem-like cells. In addition, microglial cells,which can contribute up to 30% of a brain tumor mass,play a role in glioblastoma cell invasion. Moreover, non-neoplastic astrocytes can be converted into a reactive phenotype by the glioma microenvironment and can then secrete a number of factors which influences tumor biology. The young brain may have the capacity to inhibit gliomagenesis by the endogenous neural precursor cells, which secrete tumor suppressive factors. The factors, pathways, and interactions described in this review provide a new prospective on the cell biology of primary brain tumors, which may ultimately generate new treatment modalities. However, our picture of the multiple interactions between parenchymal and tumor cells is still incomplete.

Immunology in the clinic review series; focus on cancer: glycolipids as targets for tumour immunotherapy

Research into aberrant glycosylation and over-expression of glycolipids on the surface of the majority of cancers, coupled with a knowledge of glycolipids as functional molecules involved in a number of cellular physiological pathways, has provided a novel area of targets for cancer immunotherapy. This has resulted in the development of a number of vaccines and monoclonal antibodies that are showing promising results in recent clinical trials.

Molecular targeted approaches for treatment of pancreatic cancer

Human pancreatic cancer remains a highly malignant disease with almost similar incidence and mortality despite extensive research. Many targeted therapies are under development. However, clinical investigation showed that single targeted therapies and most combined therapies were not able to improve the prognosis of this disease, even though some of these therapies had excellent anti-tumor effects in pre-clinical models. Cross-talk between cell proliferation signaling pathways may be an important phenomenon in pancreatic cancer, which may result in cancer cell survival even though some pathways are blocked by targeted therapy. Pancreatic cancer may possess different characteristics and targets in different stages of pathogenesis, maintenance and metastasis. Sensitivity to therapy may also vary for cancer cells at different stages. The unique pancreatic cancer structure with abundant stroma creates a tumor microenvironment with hypoxia and low blood perfusion rate, which prevents drug delivery to cancer cells. In this review, the most commonly investigated targeted therapies in pancreatic cancer treatment are discussed. However, how to combine these targeted therapies and/or combine them with chemotherapy to improve the survival rate of pancreatic cancer is still a challenge. Genomic and proteomic studies using pancreatic cancer samples obtained from either biopsy or surgery are recommended to individualize tumor characters and to perform drug sensitivity study in order to design a tailored therapy with minimal side effects. These studies may help to further investigate tumor pathogenesis, maintenance and metastasis to create cellular expression profiles at different stages. Integration of the information obtained needs to be performed from multiple levels and dimensions in order to develop a successful targeted therapy.

Phase 1 experience with an anti-glycotope monoclonal antibody, RAV12, in recurrent adenocarcinoma

PURPOSE

RAV12 is a high affinity, internalizing, chimeric IgG1 monoclonal antibody that binds RAAG12, a novel primate-restricted N-linked carbohydrate epitope present on multiple cell surface proteins. RAAG12 is highly expressed on many adenocarcinomas, particularly those of gastrointestinal origin. A phase 1 dose-escalation safety and pharmacokinetics trial was conducted in patients with metastatic or recurrent adenocarcinomas.

EXPERIMENTAL DESIGN

RAV12 was initially given i.v. weekly x4, then by fractionated dosing twice or thrice weekly. Thirty-three patients were treated in the dose escalation segment of the trial in the following cohorts: 0.3 mg/kg qw (6), 1.0 mg/kg qw (8), 1.5 mg/kg qw (7); and 0.5 mg/kg biw (3), 0.75 mg/kg biw (3), and 0.5 mg/kg tiw (6). Twenty patients were enrolled in a maximum tolerated dose cohort expansion at 0.75 mg/kg biw.

RESULTS

Two clinical syndromes were associated with drug administration: abdominal cramping pain with diarrhea, and asymptomatic, self-limited increases of liver function tests. These effects were partially ameliorated with fractionated dosing. Pharmacokinetics was dose dependent. Maximum concentration was reduced, whereas area under the concentration versus time curve was maintained with fractionated dosing. One patient with colorectal cancer experienced a durable partial remission, with a time to progression (TTP) of >8 months. Three additional patients experienced a TTP of >4 months.

CONCLUSIONS

RAV12 has activity in recurrent adenocarcinomas. However, the safety profile of the antibody seems to preclude the delivery of highly efficacious doses. Re-engineering the molecule to remove FcRn binding (while maintaining FcgammaR binding) and to humanize it may improve the toxicity profile and efficacy.

The RAV12 monoclonal antibody recognizes the N-linked glycotope RAAG12: expression in human normal and tumor tissues

CONTEXT

RAAG12 is a primate-restricted N-linked carbohydrate antigen present on multiple membrane-associated proteins. RAAG12 is recognized by the RAV12 monoclonal antibody. RAV12 binds to RAAG12-expressing gastrointestinal adenocarcinomas, modifies growth factor-mediated signaling, induces oncotic cell death in vitro, and has antitumor activity toward gastrointestinal tumor xenografts.

OBJECTIVE

To determine the expression pattern of RAAG12 in normal and tumor tissue to identify indications for clinical study and potential safety issues.

DESIGN

Immunohistochemistry of 36 normal human tissues and a broad range of tumor tissues to profile RAAG12 expression.

RESULTS

More than 90% of colon, gastric, and pancreatic adenocarcinomas expressed RAAG12, and expression was uniform in most samples. Expression of RAAG12 at lower frequency and/or uniformity was observed in other cancers, including esophageal, ovarian, liver, breast, and prostate carcinomas and adenocarcinomas. Similar RAAG12 expression was observed between primary and metastatic colon adenocarcinomas. No staining was seen on cardiovascular, endocrine, neuromuscular, hematopoietic, or nervous system tissue from non-tumor-bearing individuals. RAAG12 was expressed on mucosal and glandular/ductal epithelium. The gastrointestinal tract mucosa and pancreatic/biliary ducts displayed the most uniform reactivity. RAAG12 exhibited differential subcellular localization in these normal, compared with tumor, tissues. Normal polarized epithelia primarily displayed apical membrane and cytoplasmic staining, whereas tumors exhibited whole membrane staining that increased with decreasing differentiation.

CONCLUSIONS

High expression of RAAG12 on tumors of gastrointestinal origin suggests these cancers are appropriate targets for RAV12 therapy. Differential subcellular location of RAAG12 on normal epithelia may limit accessibility of RAV12 to the subset of normal tissues that exhibit antigen expression.

Monoclonal antibodies in the treatment of pancreatic cancer

Human pancreatic cancer is a malignant disease with almost equal incidence and mortality. Effective diagnostic and therapeutic strategies are still urgently needed to improve its survival rate. With advances in structural and functional genomics, recent work has focused on targeted molecular therapy using monoclonal antibodies. This review summarizes the target molecules on the tumor cell surface and normal tissue stroma, which are related to pancreatic cancer oncogenesis, tumor growth or resistance to chemotherapy, as well as molecules involved in regulating inflammation and host immunoresponses. Targeted molecules include cell-surface receptors, such as the EGF receptor, HER2, death receptor 5 and IGF-1 receptor. Effects of monoclonal antibodies against these target molecules alone or in combination with chemotherapy, small-molecule signal transduction inhibitors, or radiation therapy are also discussed. Also discussed are the use of toxin or radioisotope conjugates, and information relating to the use of these targeting agents in pancreatic cancer clinical trials. Although targeted molecular therapy with monoclonal antibodies has made some progress in pancreatic cancer treatment, especially in preclinical studies, its clinical application to improve the survival rate of pancreatic cancer patients requires further investigation.