Detection of disseminated cancer cells in bone marrow of gastric cancer using real time quantitative reverse transcriptase polymerase chain reaction

Construction of fluorescence logic gates responding to telomerase and miRNA based on DNA-templated silver nanoclusters and the hybridization chain reaction

In this study, we have developed novel fluorescence logic gates for simultaneous analysis of telomerase activity and miRNA. An imperfectly complementary duplex is assembled which can be destroyed by telomerase catalyzed extension or miRNA mediated strand displacement. The released single-stranded DNA further initiates the subsequent hybridization chain reaction. The output response of the OR gate originates from fuel strand-templated silver nanoclusters (AgNCs). On the other hand, a three-way junction is constructed for the AND gate, which can be destroyed in the presence of miRNA and telomerase. The finally released DNA is also applied to trigger the hybridization chain reaction for the generation of a fluorescence response. The constructed logic gates are sensitive and reliable in the analysis of telomerase and miRNA for potential practical applications.

[Micrometastasis in Gastric Cancer]

Although the incidence and mortality rate of gastric cancer have been steadily declining, gastric cancer is still the fourth most common cancer in the world and more than 50% of cases occur in Eastern Asia. In Korea, gastric cancer is the second most common cancer and third cause of cancer related death. The standard surgical procedure for resectable advanced gastric cancer is D2 lymphadenectomy with radical gastrectomy. Even though R0 resection was completed, recurrence is relatively common, and contributes to the limited survival of the patients in gastric cancer. As a clinically relevant factor for detection of the recurrence, the presence of isolating tumor cells has been introduced and it is so called as 'micrometastasis'. Numerous immunohistochemistry and molecular studies have shown that micrometastasis can be demonstrated not only in lymph nodes but also in such body compartments as the bone marrow, peritoneal cavity and blood. Herein, we review the current knowledge and evidence of the prognostic significance of micrometastasis in peritoneal, lymph node, bone marrow. Also, we discuss the current state of research on the circulating tumor cell in peripheral blood.

Circulating micrometastases of esophageal cancer detected by carcinoembryonic antigen mRNA reverse transcriptase-polymerase chain reaction: clinical implications

In some patients without distant metastases according to conventional preoperative investigations, relapse occurs in distant organs within a few years after radical resection of esophageal cancer. Various attempts have been made to detect micrometastases that are not found by conventional techniques. A quantitative real-time reverse-transcriptase polymerase chain reaction was used to detect messenger RNA for carcinoembryonic antigen in 147 blood samples from 49 patients scheduled for radical resection of esophageal cancer at Juntendo University Hospital between September 2003 and June 2004. The number of circulating cancer cells was assessed and the clinical significance of detecting such micrometastases was analyzed. Multivariate analysis showed that positivity of this assay was significantly associated with pT1 or pT2 disease and stage III or stage IV disease. Patients with more than 40-50 carcinoembryonic antigen mRNA copies among 10(4) normal cells on quantitative analysis had a higher recurrence rate. The number of tumor cells circulating in the blood may have more influence on the prognosis of esophageal cancer than the presence of tumor cells.

Clinical significance of cytokeratin positive cells in bone marrow of gastric cancer patients

Bone marrow (BM) is a prognostically relevant indicator organ of micrometastasis; however, the clinical importance of BM micrometastasis in gastric cancer patients is not yet known. In the present study, the BM of 267 consecutive patients with primary gastric cancer was examined for tumor cells using immunocytochemical techniques. Real-time quantitative RT-PCR was used to ensure that the tumor cells were detected properly. Among the 267 cases analyzed, 30 cases (11.2%) had cytokeratin-positive cells in the bone marrow. Positive findings were related to the tumor stage (P<0.05) and to the prominent depth of invasion (P<0.05). All patients with liver metastasis at operation had cytokeratin-positive cells in the BM. Recurrence of the disease was confirmed in 50 cases (18.7%); 4 of 30 (13.3%) in the cytokeratin-positive group and 46 of 237 (19.4%) in the cytokeratin-negative group. There were no significant differences in the 5-year survival rates between the cytokeratin-positive and cytokeratin-negative groups. Our study shows that BM micrometastasis increases according to tumor progression; however, only a subset of cancer cells may survive in the BM and finally evolve to a clinically apparent disease. Therefore it does not accurately predict the prognosis or recurrence of the disease.

Detection of cancer cells disseminated in bone marrow using real-time quantitative RT-PCR of CEA, CK19, and CK20 mRNA in patients with gastric cancer

BACKGROUND

To determine the significance of bone marrow disseminated tumor cells in gastric cancer, we investigated the mRNA expression levels of carcinoembryonic antigen (CEA), cytokeratin 19 (CK19), and cytokeratin 20 (CK20) using the real-time quantitative reverse-transcription polymerase chain reaction (RQ-PCR).

METHODS

Bone marrow samples were aspirated from the sternum at the time of surgery in 65 patients with resectable gastric cancer. Total RNA was extracted from bone marrow; and the expression levels of CEA, CK19, and CK20 mRNA were determined by RQ-PCR using an ABI PRISM 7000 and quantified against the GAPDH mRNA level.

RESULTS

The detection limits of these genes were determined in the gastric cancer cell line MKN-45 and the colon cancer cell line C-1, which had been serially diluted in peripheral blood mononuclear cells (PBMCs). A rate of 1 cancer cell/million PBMCs was obtained by detecting CEA and CK19 mRNA in MKN-45 and by detecting CK20 mRNA in C-1. In the clinical samples, only 1 of the 65 gastric cancer patients (1.5%) who had stage IV disease was positive for CEA, CK19, and CK20 mRNA; none of CEA, CK19, or CK20 mRNA was positive in the remaining 64 patients. No significant correlation was observed between disseminated cancer cells in bone marrow and clinicopathological features, including simultaneous or metachronous hepatic metastasis and patient survival.

CONCLUSION

The incidence of disseminated cancer cells in bone marrow in our study appears low, unlike that in previous reports. The significance of disseminated cancer cells in bone marrow may also be quite low in gastric cancer.

Quantitative real-time RT-PCR detection for CEA, CK20 and CK19 mRNA in peripheral blood of colorectal cancer patients

This study is aimed at establishing a sensitive approach to detect disseminated tumor cells in peripheral blood and evaluate its clinical significance. A total of 198 blood samples including 168 from colorectal carcinoma (CRC) patients and 30 from healthy volunteers were examined by quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR) to evaluate the expression of carcinoembryonic antigen (CEA), cytokeratin 20 (CK20) and cytokeratin 19 (CK19) mRNA. CEA mRNA was detected in 35.8% of patients and 3.3% of controls, CK20 mRNA in 28.3% of patients and 6.7% of controls, and CK19 mRNA in 41.9% of patients and 3.3% of controls. CEA and CK20 mRNA positive ratio increased with the advancing Dukes stages, but there was no significant difference in positive ratio between any two stages (P>0.05). Also, relatively high positive ratio of CEA, CK20 and CK19 mRNA expression was observed in some CRC patients with earlier Dukes stages. A higher positive ratio was obtained when two or three detection markers were combined compared to a single marker. Our study indicates that quantitative real-time RT-PCR detection for CEA, CK20 and CK19 mRNA in peripheral blood is a valuable tool for monitoring early stage dissemination of CRC cells in blood circulation.

Detection of Micrometastatic Disease in Bone Marrow: Is It Ready for Prime Time?

Minimal residual disease (MRD), or isolated tumor cells (ITCs) in bone marrow, may be the source of potentially fatal overt distant metastases in solid tumors even years after primary treatment. MRD can be detected by immunohistochemical methods using antibodies directed against cytokeratins or cell-surface markers or molecular, polymerase chain reaction-based techniques. Among solid tumors, the clinical relevance of MRD has been most extensively studied in breast cancer patients. Recently, the highest level of evidence for the prognostic impact of MRD in primary breast cancer was reached by a pooled analysis comprising more than 4,000 patients, showing poor outcome in patients with MRD at primary therapy. Yet the clinical application of MRD detection is hampered by the lack of a standardized detection assay. Moreover, clinical trial results demonstrating the benefit of a therapeutic intervention determined by bone marrow status are still absent. Recent results suggest that, in addition to its prognostic impact, MRD can be used for therapy monitoring or as a potential therapeutic target after phenotyping of the tumor cells. Persistent MRD after primary treatment may lead to an indication for extended adjuvant therapy. However, until clinically relevant data regarding successful therapy of MRD are available, treatment interventions on the basis of MRD should only be performed within clinical trials.

Disseminated tumor cells in the blood of patients with gastric cancer are an independent predictive marker of poor prognosis

OBJECTIVE

Gastric cancer carries a poor prognosis even after curative resection (R0). Tumor progression in gastric cancer patients has been attributed to the persistence of disseminated tumor cells (DTC) in various body compartments as a sign of minimal residual disease, although the prognostic relevance of DTC is still unclear. In this study the prognostic relevance of DTC in the blood of gastric cancer patients was investigated.

MATERIALS AND METHODS

Venous blood samples of 70 cancer patients were taken intraoperatively before surgical manipulation and examined by reverse transcription-polymerase chain reaction (RT-PCR) for expression of cytokeratin 20 (CK20) as a marker for DTC. Tumor-related survival was analyzed using univariate and multivariate models assessing occurrence of DTC, residual tumor classification, and tumor stage. Median follow-up was 20 months (range 1-57 months).

RESULTS

Twenty-eight of the 70 patients (40%) were CK20 positive. The prevalence of DTC in patients following R0 resection (15/41, 37%) was similar to that in patients with residual tumor (13/29, 45%, NS). Furthermore, expression of CK20 was independent of TNM stage. Univariate analysis of R0-resected patients revealed CK20 to be a marker for significantly shorter tumor-related survival (p = 0.0363). In a multivariate analysis, CK20 was an independent prognostic marker. Detection of CK20 had greatest impact for early tumor stages (T1 and T2, N0; p < 0.0032).

CONCLUSIONS

Detection of DTC in venous blood of gastric cancer patients is an independent predictive marker of poor prognosis and thus could help to define patients for adjuvant therapy with this tumor entity.

Clinical significance of bone marrow micrometastases in esophageal cancer

Using the reverse transcriptase-polymerase chain reaction (RT-PCR), we investigated the clinical significance of bone marrow micrometastases in patients with esophageal cancer. Bone marrow samples from 57 patients with esophageal cancer, who underwent esophagotomy, were investigated by specific RT-PCR for carcinoembryonic antigens (CEA). A total of 40 out of 57 patients (70.1%) were positive for CEA mRNA in the bone marrow. Among curatively resected cases, 34 of 50 patients (68.0%) were positive for CEA. Ten of 13 T1 patients (76.9%) were positive for CEA. Although the CEA-positive rate was high, there was no significant correlation between CEA positivity and any clinical characteristics. Among the 40 CEA-positive patients, 50% have shown recurrence so far. Detection of cancer cells in the bone marrow by RT-PCR may not always correspond to the malignant potential or other characteristics of the tumor. CEA-positive 'micrometastases' might actually represent isolated circulating tumor cells without much biological significance.

Overexpression of dopa decarboxylase in peritoneal dissemination of gastric cancer and its potential as a novel marker for the detection of peritoneal micrometastases with real-time RT-PCR

We previously performed a global analysis of the gene expression of gastric cancer cell lines established from metastases to the peritoneal cavity with the cDNA microarray method, which made it possible to analyse the expression of approximately 21 168 genes for the identification of novel markers for the detection of micrometastases in the peritoneal cavity. One of the upregulated genes is dopa decarboxylase (DDC), which is responsible for the synthesis of the key neurotransmitters dopamine and serotonine. We have examined its potential as a novel marker for the detection of peritoneal micrometastases of gastric cancer.

DDC mRNA in the peritoneal wash from 112 gastric cancer patients was quantified for comparison of carcinoembryonic antigen (CEA) mRNA by means of real-time reverse transcriptase–polymerase chain reaction (RT–PCR) with a fluorescently labelled probe to predict peritoneal recurrence. The quantity of DDC and CEA correlated with wall penetration. Real-time RT–PCR could quantitate 10–10⁶ DDC-expressing gastric cancer cells per 10⁷ mesothelial cells. The cutoff value was set at the upper limit of the quantitative value for noncancer patients, and those above this cutoff value constituted the micrometastasis (MM+) group. Of 15 cases with peritoneal dissemination, 13 were MM+DDC (87% sensitivity), and one of 48 t1 cases was MM+ (98% specificity). DDC levels in peritoneal washes from patients with synchronous peritoneal metastases were more than 50 times higher than in those from patients without metastasis (P<0.01). For 15 cases of peritoneal dissemination (seven cases were cytologically positive), DDC was positive in 13 cases (87% sensitivity), but CEA failed to detect micrometastases in four cases (73% sensitivity), indicating that DDC is in some cases superior to CEA for the detection of peritoneal micrometastases of gastric cancer in terms of sensitivity as well as specificity, especially for poorly differentiated adenocarcinomas. A combination of CEA and DDC improved the accuracy of diagnosis up to 94%.

These results suggest that DDC is potentially a novel marker for peritoneal dissemination of gastric cancer and that quantitative RT–PCR of DDC is reliable and efficient for the selection of patients for adjuvant intraperitoneal chemotherapy to prevent peritoneal recurrence.

Decreased expression of osteopontin is related to tumor aggressiveness and clinical outcome of intrahepatic cholangiocarcinoma

BACKGROUND

Osteopontin (OPN) is known to be a secreted adhesive glycoprotein. Recent studies have reported that the overexpression of OPN is correlated with tumorigenesis, tumor aggressiveness, and poor prognosis in several types of human cancer. The aim of this study was to determine whether the expression of OPN in cases of intrahepatic cholangiocarcinoma (ICC) indicates the clinical outcome.

METHODS

The expression of OPN protein was investigated immunohistochemically in surgically resected specimens from 73 patients, and the level of OPN mRNA was also examined by quantitative real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) in nine samples of ICC. We examined the correlation between the expression of OPN and the clinicopathological factors, including overall survival, in patients with ICC.

RESULTS

We detected the positive expression of OPN protein in 31 of 73 (42.5%) of the primary ICCs. Negative expression of OPN protein was significantly related to lymphatic permeation, perineural invasion, intrahepatic metastasis, and lymph node metastasis (P=0.0029, 0.0072, 0.0134, and 0.0101, respectively). Overall survival was significantly lower among the patients with a negative expression of OPN than it was among those with a positive expression of OPN. The negative expression of OPN protein and the lower levels of OPN mRNA were statistically significant (P=0.0139).

CONCLUSIONS

Decreased expression of OPN is considered to be a reliable indicator of tumor aggressiveness and clinical outcome in patients with ICC.