Antisense c-myc fragments induce normal differentiation cycles in HL-60 cells

Genomic c-Myc quadruplex DNA selectively kills leukemia

c-Myc, a key regulator of cell cycle and proliferation, is commonly overexpressed in leukemia and associated with poor prognosis. Conventional antisense oligonucleotides targeting c-myc may attenuate leukemic cell growth, however, are poorly taken into cells, rapidly degraded, and have unwanted effects on normal cells. The c-myc promoter contains a guanine-rich sequence (PU27) capable of forming quadruplex (four-stranded) DNA, which may negatively regulate c-myc transcription. However, its biological significance is unknown. We show that treatment of leukemia with an oligonucleotide encoding the genomic PU27 sequence induces cell-cycle arrest and death by oncotic necrosis due to PU27-mediated suppression of c-myc mRNA/protein expression. Furthermore, PU27 is abundantly taken into cells, localized in the cytoplasm/nucleus, inherently stable in serum and intracellularly, and has no effect on normal cells. Suppression of c-myc expression by PU27 caused significant DNA damage, cell and mitochondrial swelling, and membrane permeability characteristic of oncotic necrosis. Induction of oncosis caused mitochondrial dysfunction, depletion of cellular ATP levels, and enhanced oxidative stress. This novel antileukemic strategy addresses current concerns of oligonucleotide therapeutics including problems with uptake, stability, and unintentional effects on normal cells and is the first report of selective cancer cell killing by a genomic DNA sequence.

Negative association of c-fos expression as a favorable prognostic indicator in gastric cancer

BACKGROUND AND AIMS

The onco-protein c-fos was previously linked to favorable prognosis of gastric cancer (GC) without further validations. The present study was designed to address the issue based on a cohort of Chinese patients.

METHODS

Expression of c-fos was determined by immunohistochemical staining in specimens from 58 patients with GC who underwent surgical resection. The relationships between c-fos expression and clinicopathological and prognostic variables were further evaluated.

RESULTS

Expression of c-fos in tumor epithelia was observed in 39 (67.2%) patients. The protein was also positively expressed in lymphocytes within tumors and para-tumor epithelia. Tumors with positive expression of c-fos in tumor epithelia had a smaller size and marginally earlier T stage in all patients and/or those who underwent curative resection. Univariate analysis showed that patients with positive c-fos expression in tumor epithelia had significantly prolonged overall and tumor-free survival. Cox regression analysis revealed that c-fos expression in tumor epithelia was an independent or potential independent indicator of improved prognosis in different subgroups of patients. Expression of c-fos in para-tumor epithelia and intra-tumor lymphocytes was not associated with clinicopathological variables and long-term outcomes in patients.

CONCLUSIONS

Our data demonstrated that c-fos expression was negatively associated with tumor progression and was predictive for favorable survival in patients with GC.

Recent developments in the use of adenoviruses and immunotoxins in cancer gene therapy

Despite setbacks in the past and apparent hurdles ahead, gene therapy is advancing toward reality. The past several years have witnessed this new field of biomedicine developing rapidly both in breadth and depth, especially for the treatment of cancer, thanks largely to the better understanding of molecular and genetic basis of oncogenesis and the development of new and improved vectors and technologies for gene delivery and targeting. This article is intended to provide a brief review of recent advances in cancer gene therapy using adenoviruses, both as vectors and as oncolytic agents, and some of the recent progress in the development of immunotoxins for use in cancer gene therapy.

Mining the Wnt pathway for cancer therapeutics

Aberrant activation of the Wnt pathway is implicated in driving the formation of various human cancers, particularly those of the digestive tract. Inhibition of aberrant Wnt pathway activity in cancer cell lines efficiently blocks their growth, highlighting the great potential of therapeutics designed to achieve this in cancer patients. Here we provide an overview of the promise and pitfalls of current drug development strategies striving to inhibit the Wnt pathway and present new opportunities for therapeutic intervention.