A simple method for the routine detection of somatic quantitative genetic alterations in colorectal cancer.

BACKGROUND & AIMS: Several quantitative genetic alterations have been suggested to have in colorectal cancer (CRC) either a prognostic or a therapeutic predictive value. Routine detection of these alterations is limited by the absence of simple methods.

METHODS

The somatic quantitative multiplex polymerase chain reaction of short fluorescent fragments (QMPSF) is based on the simultaneous amplification under quantitative conditions of several dye-labeled targets both from tumor and nonmalignant tissues. For each patient, the resulting QMPSF fluorescent profiles are superimposed, and quantitative changes are simply detected by an increase or decrease of the corresponding fluorescent peaks. Two assays were developed and applied to 57 CRC: a "bar code" exploring several loci with known prognostic value and a "kinogram" studying the copy number change of kinase genes, against which inhibitors have been developed.

RESULTS

The bar code revealed that the most frequent alterations were the gain of AURKA/20q13 (53%) and MYC/8q24 (39%) and heterozygous deletion of DCC/18q21.3 (39%) and TP53/17p13 (23%). The kinogram detected a gene copy number increase for AURKA, PTK2, MET, and EGFR in 53%, 37%, 33%, and 28% of the tumors, respectively. QMPSF results were validated by comparative genomic hybridization and multiplex real-time polymerase chain reaction on genomic DNA.

CONCLUSIONS

The somatic QMPSF is a simple method able to detect simultaneously on a routine basis several quantitative changes in tumors. Its flexibility will allow the integration of clinically relevant genes. This high throughput method should be a valuable complementary tool of fluorescent in situ hybridization and comparative genomic hybridization.