Gene therapy for pancreatic cancer targeting the genomic alterations of tumor suppressor genes using replication-selective oncolytic adenovirus

Biosynthesis and Biological Activity of Carbasugars

The first synthesis of carbasugars, compounds in which the ring oxygen of a monosaccharide had been replaced by a methylene moiety, was described in 1966 by Professor G. E. McCasland’s group. Seven years later, the first true natural carbasugar (5a-carba-R-D-galactopyranose) was isolated from a fermentation broth of Streptomyces sp. MA-4145. In the following decades, the chemistry and biology of carbasugars have been extensively studied. Most of these compounds show interesting biological properties, especially enzymatic inhibitory activities, and, in consequence, an important number of analogues have also been prepared in the search for improved biological activities. The aim of this review is to give coverage on the progress made in two important aspects of these compounds: the elucidation of their biosynthesis and the consideration of their biological properties, including the extensively studied carbapyranoses as well as the much less studied carbafuranoses.

Structural basis of mapping the spontaneous mutations with 5-flurouracil in uracil phosphoribosyltransferase from Mycobacterium tuberculosis

Tuberculosis (TB) remains the second leading cause of death from an infectious disease globally, despite the incessant efforts to control it. Research and development into new TB medicines is imperative for effective TB control; however, new strategies for the rational use of existing drugs, such as through the identification of new drug targets, could also significantly enhance this process. Key enzymes involved in the essential metabolic and regulatory pathways are usually sought in the pursuit of potential drug targets. Uracil phosphoribosyltransferase (UPRT) is a key salvage pathway enzyme in the synthesis of uridine 5'-monophosphate (UMP) and a probable target of 5-fluorouracil (5-FU) in Mycobacterium tuberculosis (Mtb). To date, there is no structure available for UPRT from Mtb (MtUPRT) that would assist in the identification of appropriate inhibitors for the enzyme. Here we report the structure of MtUPRT along with its spontaneous mutational studies in the presence of 5-FU. We further mapped these four single nucleotide polymorphisms (SNPs) onto the MtUPRT structure, with two residues found to be conserved among the MtUPRT homologs. Notably, none of these SNPs are located in the 5-FU binding pocket. However, the mutants harboring these mutations showed increased MICs (minimum inhibitory concentration) as compared to wild type strains. The present study will aid in the screening of inhibitors of MtUPRT and thus assist in TB drug design and development.

From scourge to cure: tumour-selective viral pathogenesis as a new strategy against cancer

Tumour mutations corrupt cellular pathways, and accumulate to disrupt, dysregulate, and ultimately avoid mechanisms of cellular control. Yet the very changes that tumour cells undergo to secure their own growth success also render them susceptible to viral infection. Enhanced availability of surface receptors, disruption of antiviral sensing, elevated metabolic activity, disengagement of cell cycle controls, hyperactivation of mitogenic pathways, and apoptotic avoidance all render the malignant cell environment highly supportive to viral replication. The therapeutic use of oncolytic viruses (OVs) with a natural tropism for infecting and subsequently lysing tumour cells is a rapidly progressing area of cancer research. While many OVs exhibit an inherent degree of tropism for transformed cells, this can be further promoted through pharmacological interventions and/or the introduction of viral mutations that generate recombinant oncolytic viruses adapted to successfully replicate only in a malignant cellular environment. Such adaptations that augment OV tumour selectivity are already improving the therapeutic outlook for cancer, and there remains tremendous untapped potential for further innovation.

Identification and characterization of a novel anticancer agent with selectivity against deleted in pancreatic cancer locus 4 (DPC4)-deficient pancreatic and colon cancer cells

OBJECTIVES

The deleted in pancreatic cancer locus 4 (DPC4)/SMAD4 tumor suppressor gene is frequently inactivated in pancreatic (approximately 55%) and colorectal cancers (approximately 30%). Like other tumor suppressor genes, the loss-of-function mutations found in the DPC4 gene are specific to cancer cells. This provides an attractive and unique opportunity for therapeutic intervention. The aim of this study was to identify and characterize small molecules that selectively kill DPC4-deficient cancer cells.

METHODS

An unbiased chemical screening using isogenic cell lines that only differ in the DPC4 gene was carried out to identify positive hits. Selected hits were further verified in additional isogenic cell lines and characterized in cancer cells using several different cellular assays.

RESULTS

A lead molecule, UA62784, was identified to be selectively cytotoxic against cancer cells with deficient DPC4. UA62784 preferentially induces cell cycle arrest and apoptosis in cells with deficient DPC4. It also selectively reduces the clonogenicity of DPC4-deficient cells on soft agar when compared with cells with wild type DPC4. We further demonstrate that UA62784 induces CDC2 kinase activity preferentially in DPC4-negative cells.

CONCLUSIONS

UA62784 is a small molecule that selectively kills DPC4-deficient cancer cells. Its potent activity and relatively low molecular weight make it a decent candidate for further lead optimization.

Regional administration of oncolytic Echovirus 1 as a novel therapy for the peritoneal dissemination of gastric cancer

The dissemination of malignant gastric cells to the peritoneum occurs frequently, usually as an early event in disease, and results in poor patient prognosis. Surgery and chemotherapy offer limited therapeutic success. The low-pathogenic human enterovirus, Echovirus 1 (EV1), is an oncolytic virus that selectively targets and destroys malignant prostate and ovarian cancer xenografts in vivo. Lytic EV1 infection requires the cell surface expression of alpha(2)beta(1), an integrin involved in the dissemination of gastric cancer cells to the peritoneum. Herein, we evaluated the capacity of EV1 for anti-neoplastic cell action in gastric peritoneal carcinomatosis. Flow cytometric analysis demonstrated that alpha(2)beta(1) was abundantly surface expressed on a panel of gastric cancer cell lines, rendering the majority of lines highly susceptible to in vitro lytic EV1 infection and supportive of efficient viral progeny production. A bioluminescent MKN-45-Luc SCID mouse model of peritoneal dissemination was developed to allow real-time non-invasive monitoring of peritoneal tumor burden. Employing this mouse model, we demonstrated a therapeutic dose-response for escalating oncolytic EV1 doses. Taken together, these results emphasize the exciting potential for EV1 as a single or adjunct therapy for the control of the peritoneal dissemination of gastric cancer.

Biological approaches to therapy of pancreatic cancer

Pancreatic cancer is a lethal disease and notoriously difficult to treat. Only a small proportion is curative by surgical resection, whilst standard chemotherapy for patients with advanced disease has only modest effect with substantial toxicity. Clearly there is a need for the continual development of novel therapeutic agents to improve the current situation. Improvement of our understanding of the disease has generated a large number of studies on biological approaches targeting the molecular abnormalities of pancreatic cancer, including gene therapy and signal transduction inhibition, antiangiogenic and matrix metalloproteinase inhibition, oncolytic viral therapy and immunotherapy. This article provides a review of these approaches, both investigated in the laboratories and in subsequent clinical trials.

Adenoviral p53 gene transfer and gemcitabine in three patients with liver metastases due to advanced pancreatic carcinoma

BACKGROUND

Current therapies for adenocarcinoma of the pancreas do not improve the life expectancy of patients.

METHODS

In a non-randomized pilot trail we tested whether a local therapy based upon an adenoviral gene transfer of wild type p53 in combination with gemcitabine administration would be safe in patients with liver metastases due to pancreatic carcinoma. We report on the clinical course of three patients with respect to safety, tolerability and tumor response.

RESULTS

Transient grade III toxicities occurred with fever, leucopenia, elevation of AP, ALT, AST, GGT, while grade IV toxicity occurred for bilirubin only. Laboratory tests suggested disseminated intravascular coagulation in all three patients, but fine needle biopsies of liver did not show any histological evidence of thrombus or clot formation. Progression of liver metastases was documented in one and stable disease in another patient two months after treatment. However, a major improvement with regression of the indexed lesion by 80% occurred in a third patient after a single administration of 7.5 x 10(12) viral particles, and time to progression was extended to six months.

CONCLUSION

The combination therapy of viral gene transfer and chemotherapy temporarily controls and diminishes tumor burden. Improvement of the toxicity profile is necessary. Further trials are warranted to improve treatment and life expectancy of patients suffering from fatal diseases such as pancreatic carcinoma.