Antisense Oligodeoxynucleotide Directed against c-myb Has Anticancer Activity and Potentiates the Antiproliferative Effect of Conventional Anticancer Drugs Acting by Different Mechanisms in Human Colorectal Cancer Cells

Abstract

The c-myb proto-oncogene encodes a DNA-binding protein with transactivation properties that plays an important regulatory role in cell proliferation and differentiation. Overexpression of c-myb in colonic tumors compared to normal mucosa suggests that c-myb may play a role in the malignant transformation of colonic mucosa and that inhibition of c-myb expression may suppress, to some extent, the proliferation of neoplastic cells. Complete suppression of tumor cell proliferation may require inhibition of multiple growth-promoting genes. Alternatively, the combination of oncogene-targeted oligodeoxynucleotides (ODNs) with standard cytotoxic agents might represent a useful therapeutic approach to improving cancer treatment. In the present study, we have investigated whether the inhibition of a growth-promoting gene, namely c-myb, affects the sensitivity of human colorectal cancer cells, in vitro, to conventional chemotherapeutic drugs: taxol, 5-fluorouracil, vinblastine and doxorubicin. We show that c-myb antisense phosphorothioate (S) ODN treatment induces growth arrest in the G₁/G₂ phases of the cell cycle and inhibits cell proliferation in a dose- and time-dependent manner. Also, treatment with c-myb antisense (S)ODN decreases c-myb mRNA and protein expression. A greater inhibition of cell proliferation in vitro was obtained with the combination of c-myb (S)ODN and cytotoxic drugs. The combinations exerted additive and synergistic effects on human colorectal cancer cells. This study suggests that c-myb antisense (S)ODN might be useful in the therapy of colorectal cancer in combination with chemotherapeutic drugs.

Transcription factor c-Myb promotes the invasion of hepatocellular carcinoma cells via increasing osteopontin expression

“…Antisense oligodeoxynucleotides targeting c-Myb, a dominant negative c-Myb or c-Myb vaccine has shown an effective approach for therapy of c-Myb dependent haematopoietic and epithelial malignancies [31-33]. …”

c-<i>myc</i> Antisense Oligonucleotides Sensitize Human Colorectal Cancer Cells to Chemotherapeutic Drugs

“…[S]ODNs were chosen because their chemistry possesses greater intracellular stability than phosphodiester ODNs, to reduce the deleterious effect from the endogenous nucleases and to provide constant AS exposure [23] .…”

“…The cell cycle phase (G 0 -G 1 , S, G 2 /M) distribution was determined using flow cytometry by measurement of the DNA content of nuclei labeled with propidium iodide as previously described [23] . The tested cells were collected by trypsinization and then washed with cold phosphate-buffered saline and counted with a cell counter.…”

“…The levels of c-myc protein in human colorectal cancer cells, either untreated or treated with c-myc AS or sense [S]ODNs (8 M ), were determined as previously described [23] . Briefly, 1-2 !…”

Interfering with Cancer: A Brief Outline of Advances in RNA Interference in Oncology

“…There have been many practical constraints using antisense that have now limited its application in cancer gene therapy. Although it may not represent the 21st century's single cure, there is still considerable mileage left in the technology [12][13][14]. Nevertheless, attention has now shifted onto a more recent discovery in gene silencing, namely RNA interference (RNAi).…”