Impact of disseminated tumor cells in gastrointestinal cancer

Circulating tumour cells as a predictive factor for response to systemic chemotherapy in patients with advanced colorectal cancer

Circulating tumour cells (CTC) can be traced in patients with different types of cancer. The aim of this study was to detect CTC in patients with advanced colorectal cancer and whether CTC are still detectable after systemic chemotherapy. Blood from 34 patients with advanced colorectal cancer was analysed for the presence of CTC before chemotherapy was given and after 3 months. Eleven patients demonstrated a tumour remission after chemotherapy. In 6 cases CTC were detectable before but not after initiation of chemotherapy. Ten patients demonstrated a progression. In 5 cases CTC were detected before and after chemotherapy. Our data suggest that the detection of CTC will help to identify patients responding to chemotherapy or with a risk of a therapy failure.

Immunomagnetic CD45 depletion does not improve cytokeratin 20 RT-PCR in colorectal cancer

BACKGROUND

Cytokeratin 20 reverse transcriptase polymerase chain reaction (CK20 RT-PCR) of blood and bone marrow specimens has been suggested for assessment of hematogenously disseminated tumor cell (DTC) spread in colorectal cancer (CRC) patients. Considerable discrepancies among the studies reported indicate a need for better evaluation procedures. We investigated whether mononucleated cell (MNC) enrichment by Ficoll density gradient centrifugation followed by immunomagnetic depletion of CD45-positive cells (extended enrichment) allows better detection of DTC-associated CK20 mRNA compared to MNC enrichment by Ficoll density gradient centrifugation alone (Ficoll enrichment).

METHODS

We analyzed 53 samples [38 peripheral blood (PB), 15 bone marrow (BM)] from 38 CRC patients. Extended enrichment was performed for 30 specimens (PB and BM, n=15 each), and Ficoll enrichment for 23 blood specimens. Total RNA was extracted, reverse-transcribed and analyzed by real-time RT-PCR using a LightCycler instrument.

RESULTS

Despite extended enrichment, 10 PB and 8 BM samples could not be analyzed because of low cellular yield. The depletion efficiency of CD45 separation was 2 log. RT-PCR of the housekeeping gene PBGD resulted in high and varied crossing point values (mean 37.1+3.0) for five PB and seven BM specimens. Ficoll enrichment yielded 23 analyzable blood specimens for which the mean crossing point value was 26.7+0.5 in PBGD RT-PCR. CK20 RT-PCR of 23 blood samples (all from Dukes D patients) revealed CK20 transcripts in four cases (17%).

CONCLUSIONS

Extended enrichment was not superior to Ficoll enrichment; in fact, the sensitivity was lower. Improvement of the reported CK20 RT-PCR assay of Ficoll-enriched MNC populations is warranted.