Detection of cytokeratins 19/20 and guanylyl cyclase C in peripheral blood of colorectal cancer patients

Detection and clinical significance of occult tumour cells in colorectal cancer

BACKGROUND

A variety of techniques have been employed for the detection of occult tumour cells in the blood, bone marrow and lymph nodes of patients with colorectal cancer. This review examines the methods used, results obtained and the clinical significance of studies in this field.

METHODS

A Medline literature search was performed using the terms colorectal cancer, minimal residual disease, micrometastasis, polymerase chain reaction, reverse transcriptase polymerase chain reaction and immunocytochemistry; further references were obtained from key articles.

RESULTS

Immunocytochemical examination of bone marrow is the benchmark for detecting clinically significant occult disease. Larger standardized studies are required to confirm the prognostic significance of molecular assays for the detection of tumour cells in blood and bone marrow. The prognostic significance of lymph node tumour cells detected by either immunohistochemical or molecular methods awaits further affirmation.

CONCLUSION

Standardization of terminology and techniques used, combined with large prospective clinical studies, is required if detection of occult residual disease is to become a prognostic marker for recurrence in colorectal cancer.

Ectopic expression of guanylyl cyclase C in CD34+ progenitor cells in peripheral blood

PURPOSE

To examine the utility of guanylyl cyclase C (GC-C)-specific nested reverse transcriptase polymerase chain reaction (RT-PCR) to detect circulating tumor cells in patients with colorectal cancer.

PATIENTS AND METHODS

Peripheral-blood mononuclear cells from 24 patients with Dukes' stage D colorectal cancer were analyzed by GC-C-specific nested RT-PCR using 1 microg of total RNA. Peripheral-blood mononuclear cells from 20 healthy volunteers served as controls. Additionally, peripheral-blood CD34+ progenitor cells were assayed for the expression of both GC-C and other epithelial cell-specific markers.

RESULTS

GC-C mRNA was detected in blood mononuclear cells from all 24 patients with colorectal cancer and all healthy volunteers. These unexpected positive results reflected low-level ectopic transcription of GC-C in CD34+ progenitor cells. Moreover, CD34+ progenitor cells expressed other epithelial cell-specific markers, including prostate-specific antigen, prostate-specific membrane antigen, carcinoembryonic antigen, CK-19, CK-20, mucin 1, and GA733.2. Limiting the quantity of mononuclear cell total RNA analyzed to < or = 0.8 microg eliminated detection of GC-C and other tissue-specific transcripts in blood of healthy volunteers. However, under the same conditions, GC-C mRNA was detected in mononuclear cells from all 24 patients with metastatic colorectal cancer. Using 0.5 microg of total RNA and GC-C-specific primers, nested RT-PCR detected a single human colon carcinoma cell (approximately 20 to 200 GC-C transcripts/cell) in 10(6) to 10(7) mononuclear blood cells.

CONCLUSION

These data suggest that GC-C may be useful for detecting circulating colorectal cancer cells. They also demonstrate that CD34+ cells are a source of ectopically expressed epithelial cell-specific markers and that CD34+ cells may contribute to the high false-positive rate generally observed when those markers are used to detect rare circulating metastatic cancer cells by RT-PCR.

Molecular detection of tumor cells at diagnosis invading the bone marrow and peripheral blood of patients with aggressive or indolent lymphomas

We studied tumor cell invasions of bone marrow and peripheral blood in patients with various types of advanced non-Hodgkin's lymphoma by amplifying complementarity determining region III using the polymerase chain reaction (PCR) method and developing patient-specific probes. After molecular engineering, we could detect tumor cells in bone marrow from seven of 11 cases and in peripheral blood from six of 11 cases, despite negative results in four cases studied morphologically. Indolent cases were more likely to yield positive results than aggressive cases. The reason may be different biological behaviors among the histological types.

Lack of prognostic influence of circulating tumor cells in peripheral blood of patients with colorectal cancer

BACKGROUND AND AIMS

Circulating tumor cells in peripheral blood may be detected using high-sensitivity molecular techniques in several types of solid neoplasms, but their significance in colorectal cancer is controversial. The aim of this study was to assess the prognostic value of carcinoembryonic antigen (CEA) messenger RNA (mRNA) detection in peripheral blood samples from patients with colorectal cancer.

METHODS

Peripheral vein blood samples from 95 consecutive patients with histologically confirmed colorectal carcinoma were obtained immediately before surgery to determine the presence of circulating tumor cells by use of a reverse-transcription polymerase chain reaction targeting CEA mRNA. Endpoints of the study were disease-free and overall survival. Results are referred to the whole series and, more importantly, to the 68 patients who underwent surgery for cure.

RESULTS

After a median follow-up of 42 months, 19 of 68 patients (28%) operated on for cure had tumor relapse. In addition, 50 of 68 patients (73%) were alive. The probability of disease-free and overall survival was dependent on lymph node metastases and degree of differentiation, but not on the presence of circulating tumor cells (disease-free survival: relative risk, 1.00; 95% confidence interval [CI], 0.39-2.22, P = 0.99; overall survival: relative risk, 0.91, 95% CI, 0.34-2.43; P = 0.84). Similar results were obtained when all 95 patients with colorectal cancer were analyzed (disease-free survival: relative risk, 1.11; 95% CI, 0.63-1.95; P = 0.71; overall survival: relative risk, 1.21; 95% CI, 0.63-2.30, P = 0.55).

CONCLUSIONS

Preoperative detection of blood circulating tumor cells by means of reverse-transcription polymerase chain reaction of CEA does not have prognostic significance in patients with colorectal cancer.

The expression of the growth hormone secretagogue receptor ligand ghrelin in normal and abnormal human pituitary and other neuroendocrine tumors

Ghrelin is a recently identified endogenous ligand of the GH secretagogue (GHS) receptor. It was originally isolated from the stomach, but has also been shown to be present in the rat hypothalamus. It is a 28-amino acid peptide with an unusual octanoylated serine 3 at the N-terminal end of the molecule, which is crucial for its biological activity. Synthetic GHSs stimulate GH release via both the hypothalamus and the pituitary, and the GHS receptor (GHS-R) has been shown by us and others to be present in the pituitary. We investigated whether ghrelin messenger ribonucleic acid (mRNA) and peptide are present in the normal human hypothalamus and in normal and adenomatous human pituitary. RNA was extracted from pituitary tissue removed at autopsy and transsphenoidal surgery (n = 62), and ghrelin and GHS-R type 1a and 1b mRNA levels were investigated using real-time RT-PCR. Both ghrelin and GHS-R mRNA were detected in all samples. Corticotroph tumors showed significantly less expression of ghrelin mRNA, whereas GHS-R mRNA levels were similar to those in normal pituitary tissue. Gonadotroph tumors showed a particularly low level of expression of GHS-R mRNA. Immunohistochemistry, using a polyclonal antibody against the C-terminal end of the ghrelin molecule, revealed positive staining in the homolog of the arcuate nucleus in the human hypothalamus and in both normal and abnormal human pituitary. Pituitary tumor ghrelin peptide content was demonstrated using two separate RIA reactions for the N-terminal and C-terminal ends of the molecule. Both forms were present in normal and abnormal pituitaries, with 5 +/- 2.5% octanoylated (active) ghrelin (mean +/- SD) present as a percentage of the total. We suggest that the presence of ghrelin mRNA and peptide in the pituitary implies that the locally synthesized hormone may have an autocrine/paracrine modulatory effect on pituitary hormone release.

Molecular quantification and mapping of lymph-node micrometastases in cervical cancer

BACKGROUND

A proportion of patients with cancer and lymph nodes negative on histology will develop recurrence. Reverse-transcriptase PCR (RT-PCR) is a highly sensitive method for detection of lymph-node micrometastases, but accurate quantitative assessment has been difficult.

METHODS

We studied primary tumours and 156 lymph nodes from 32 patients with cervical cancer (stage IA2, IB1, and IB2) and 32 lymph nodes from nine patients with benign disease. A fully quantitative, real-time RT-PCR assay was used to document absolute copy numbers of the epithelial marker cytokeratin 19. Primers and probe were designed not to amplify either of the two cytokeratin 19 pseudogenes.

FINDINGS

All primary tumours and histologically involved lymph nodes (six) had more than 106 copies of cytokeratin 19 mRNA per microg total RNA. Expression of cytokeratin 19 (up to 1.1 x 10(5) copies per microg RNA) was detected in 66 (44%) of 150 histologically uninvolved lymph nodes, and in nodes from 16 of 32 patients with cervical cancer. 15 of these 16 patients with evidence of micrometastases had the highest cytokeratin 19 transcription level in a first lymph-node drainage station (three obturator, six internal, and six external iliac node). Transcription of cytokeratin 19 was found at a low level in just one of 32 lymph nodes obtained from nine patients with benign disease. Median copy number of cytokeratin 19 transcription was significantly higher (>10(3) copies) in association with adverse prognostic features.

INTERPRETATION

The results suggest that about 50% of early-stage cervical cancers shed tumour cells to the pelvic lymph nodes. The amount of cytokeratin 19 expression was related to clinicopathological features. Further studies are required to document the clinical implications of molecular micrometastases.

Elevated levels of RanBP7 mRNA in colorectal carcinoma are associated with increased proliferation and are similar to the transcription pattern of the proto-oncogene c-myc

We have used suppression subtractive hybridisation, "in silico" cloning and reverse Northern dot blot analysis to identify significant up-regulation of RanBP7 transcription in a human colorectal carcinoma. Quantitative RT-PCR analyses using the Taqman system demonstrated that RanBP7 mRNA levels were elevated in 47/75 colorectal tumours. There was no significant difference in 17 matched normal and tumour pairs and reduced levels in 11. Since RanBP7 specifies a key member of nuclear transport receptors responsible for the nuclear import of histone H1 and ribosomal proteins, we investigated whether this up-regulation might be proliferation-associated. RanBP7 mRNA copy numbers were significantly correlated with those of proliferating cell nuclear antigen in both normal and cancer tissue. Interestingly, the transcription pattern of the proto-oncogene c-myc showed a similar correlation with PCNA mRNA. Our results highlight the need for the careful interpretation of quantitative data that compare mRNA levels in normal and cancer tissue.

Circulating bronchoepithelial cells expressing mRNA for surfactant protein A in patients with pulmonary fibrosis

There are several unsolved clinical findings in patients with idiopathic pulmonary fibrosis (IPF); (i) predominance of fibrosis in the lower lung fields, (ii) digital clubbing, and (iii) patchy distribution of pulmonary fibrosis. To explain these unsolved problems, we hypothesized that regenerated or premature bronchoepithelial cells may circulate in the blood in patients with IPF. To prove this, we performed the reverse transcriptase-polymerase chain reaction (RT-PCR) for cytokeratin 19 (CK19) and pulmonary surfactant protein A (SPA) in peripheral blood in patients with IPF and pulmonary fibrosis associated with collagen vascular disorders. In addition, 20 patients with chronic pulmonary emphysema as a disease control and 19 normal volunteers were also evaluated for the existence of circulating bronchoepithelial cells. RT-PCR analysis showed that CK19 was expressed in 12 of 38 blood samples (31.6%) of IPF and pulmonary fibrosis associated with collagen vascular disorders, seven of 20 (35.0%) blood samples of chronic pulmonary emphysema, and four of 19 (21.1%) blood samples of normal volunteers. mRNA for SPA was positive in eight of 38 (21.1%) blood samples of IPF. In contrast, SPA expressing cells were not detected in any blood samples obtained from patients with chronic pulmonary emphysema or normal volunteers. This evidence suggests that there were some circulating bronchoepithelial cells expressing mRNA for SPA in peripheral blood of patients with IPF and pulmonary fibrosis associated with collagen vascular disorders.

Transcription of the inositol polyphosphate 1-phosphatase gene (INPP1) is upregulated in human colorectal cancer

We have used suppression subtractive hybridization to demonstrate significant overexpression of the inositol polyphosphate 1-phosphatase gene (INPP1) in colorectal cancer compared with matched normal colon epithelium. Its gene product catalyses the hydrolysis of inositol 1,3,4-trisphosphate and inositol 1, 4-bisphosphate, a key molecule in the phosphoinositide metabolic and signaling pathways. Following confirmation of the differential expression by reverse Northern dot blot analysis, fully quantitative Taqman reverse transcriptase-polymerase chain reaction assays showed that its transcription was upregulated in 42/49 colorectal tumors. There was no significant difference in four tumors and reduced transcription was observed in three. This is the first study to report the upregulation of the INPP1 gene in a human cancer and should facilitate further studies looking at the role of phosphatidylinositol signaling reactions in human colorectal cancer.