Intestinal epithelial culture under an air-liquid interface: a tool for studying human and mouse esophagi.

This study investigated whether an intestinal epithelial culture method can be applied to mouse and human esophageal cultures. The esophagi harvested from 1-day-old mice and adult humans were maintained in collagen gels. A commercially available culture medium for human embryonic stem cells was used for the human esophageal culture. We discovered that the intestinal epithelial culture method can be successfully applied to both mouse and human esophageal cultures. The long-term cultured esophageal organoids were rod-like luminal structures lined with myofibroblasts. We discovered that regeneration of the esophageal mucosal surface can be almost completely achieved in vitro, and the advantage of this method is that organoid cultures may be generated using host-derived fibroblasts as a niche. This method is a promising tool for mouse and human research in intestinal biology, carcinogenesis, and regenerative medicine.

Identification of a bona fide microRNA biomarker in serum exosomes that predicts hepatocellular carcinoma recurrence after liver transplantation.

BACKGROUND: Predictive biomarkers for the recurrence of hepatocellular carcinoma (HCC) have great benefit in the selection of treatment options, including liver transplantation (LT), for HCC. The purpose of this study was to identify specific microRNAs (miRs) in exosomes from the serum of patients with recurrent HCC and to validate these molecules as novel biomarkers for HCC recurrence. METHODS: We employed microarray-based expression profiling of miRs derived from exosomes in the serum of HCC patients to identify a biomarker that distinguishes between patients with and without HCC recurrence after LT. This was followed by the validation in a separate cohort of 59 HCC patients who underwent living related LT. The functions and potential gene targets of the recurrence-specific miRs were analysed using a database, clinical samples and HCC cell lines. RESULTS: We found that miR-718 showed significantly different expression in the serum exosomes of HCC cases with recurrence after LT compared with those without recurrence. Decreased expression of miR-718 was associated with HCC tumour aggressiveness in the validated cohort series. We identified HOXB8 as a potential target gene of miR-718, and its upregulation was associated with poor prognosis. CONCLUSION: Circulating miRs in serum exosomes have potential as novel biomarkers for predicting HCC recurrence.

Circulating tumour cell-derived plastin3 is a novel marker for predicting long-term prognosis in patients with breast cancer.

BACKGROUND: Identification of promising biomarkers that predict the prognosis of patients with breast cancer is needed. In this study, we hypothesised that the expression of the epithelial-mesenchymal transition-related biomarker plastin3 (PLS3) in peripheral blood could be a prognostic factor in breast cancer. METHODS: We examined PLS3 expression in breast cancer cell lines with epithelial and mesenchymal traits and in circulating tumour cells (CTCs) obtained from the peripheral blood of breast cancer patients. We investigated PLS3 expression in the peripheral blood of 594 patients with breast cancer to evaluate the clinical significance of PLS3 expression. RESULTS: Robust PLS3 expression was observed in different breast cancer cell lines (Hs578t, MCF-7, MDA-MB-468, and MDA-MB-231) as well as in a bone marrow derived cancer cell line (BC-M1). In both the training (n=298) and validation (n=296) sets, PLS3 expression was observed in CTCs of patients with breast cancer. PLS3-positive patients showed significantly poorer overall and disease-free survival than PLS3-negative patients (P=0.0001 and 0.003, respectively). Subset analysis revealed that this prognostic biomarker was relevant in patients with stage I-III cancer, particularly in patients with luminal-type and triple-negative-type tumours. CONCLUSIONS: These data demonstrated that PLS3 was expressed in CTCs undergoing the epithelial-mesenchymal transition in patients with breast cancer. Furthermore, PLS3 may be an excellent biomarker for identifying groups at risk of recurrence or with a poor prognosis.

Exosomal microRNA in serum is a novel biomarker of recurrence in human colorectal cancer.

BACKGROUND: Functional microRNAs (miRNAs) in exosomes have been recognised as potential stable biomarkers in cancers. The aim of this study is to identify specific miRNAs in exosome as serum biomarkers for the early detection of recurrence in human colorectal cancer (CRC). METHODS: Serum samples were sequentially obtained from six patients with and without recurrent CRC. The miRNAs were purified from exosomes, and miRNA microarray analysis was performed. The miRNA expression profiles and copy number aberrations were explored using microarray and array CGH analyses in 124 CRC tissues. Then, we validated exosomal miRNAs in 2 serum sample sets (90 and 209 CRC patients) by quantitative real-time RT-PCR. RESULTS: Exosomal miR-17-92a cluster expression level in serum was correlated with the recurrence of CRC. Exosomal miR-19a expression levels in serum were significantly increased in patients with CRC as compared with healthy individuals with gene amplification. The CRC patients with high exosomal miR-19a expression showed poorer prognoses than the low expression group (P<0.001). CONCLUSIONS: Abundant expression of exosomal miR-19a in serum was identified as a prognostic biomarker for recurrence in CRC patients.

The AURKA/TPX2 axis drives colon tumorigenesis cooperatively with MYC.

BACKGROUND: The MYC oncogene has long been established as a central driver in many types of human cancers including colorectal cancer. However, the realization of MYC-targeting therapies remains elusive; as a result, synthetic lethal therapeutic approaches are alternatively being explored. A synthetic lethal therapeutic approach aims to kill MYC-driven tumors by targeting a certain co-regulator on the MYC pathway. PATIENTS AND METHODS: We analyzed copy number and expression profiles from 130 colorectal cancer tumors together with publicly available datasets to identify co-regulators on the MYC pathway. Candidates were functionally tested by in vitro assays using colorectal cancer and normal fibroblast cell lines. Additionally, survival analyses were carried out on another 159 colorectal cancer patients and public datasets. RESULTS: Our in silico screening identified two MYC co-regulator candidates, AURKA and TPX2, which are interacting mitotic regulators located on chromosome 20q. We found the two candidates showed frequent co-amplification with the MYC locus while expression levels of MYC and the two genes were positively correlated with those of MYC downstream target genes across multiple cancer types. In vitro, the aberrant expression of MYC, AURKA and TPX2 resulted in more aggressive anchorage-independent growth in normal fibroblast cells. Furthermore, knockdown of AURKA or TPX2, or treatment with an AURKA-specific inhibitor effectively suppressed the proliferation of MYC-expressing colorectal cancer cells. Additionally, combined high expression of MYC, AURKA and TPX2 proved to be a poor prognostic indicator of colorectal cancer patient survival. CONCLUSIONS: Through bioinformatic analyses and experiments, we proposed TPX2 and AURKA as novel co-regulators on the MYC pathway. Inhibiting the AURKA/TPX2 axis would be a novel synthetic lethal therapeutic approach for MYC-driven cancers.

Amplification of PVT-1 is involved in poor prognosis via apoptosis inhibition in colorectal cancers.

BACKGROUND: We previously conducted gene expression microarray analyses to identify novel indicators for colorectal cancer (CRC) metastasis and prognosis from which we identified PVT-1 as a candidate gene. PVT-1, which encodes a long noncoding RNA, mapped to chromosome 8q24 whose copy-number amplification is one of the most frequent events in a wide variety of malignant diseases. However, PVT-1 molecular mechanism of action remains unclear. METHODS: We conducted cell proliferation and invasion assays using colorectal cancer cell lines transfected with PVT-1siRNA or negative control siRNA. Gene expression microarray analyses on these cell lines were also carried out to investigate the molecular function of PVT-1. Further, we investigated the impact of PVT-1 expression on the prognosis of 164 colorectal cancer patients by qRT-PCR. RESULTS: CRC cells transfected with PVT-1 siRNA exhibited significant loss of their proliferation and invasion capabilities. In these cells, the TGF-ß signalling pathway and apoptotic signals were significantly activated. In addition, univariate and multivariate analysis revealed that PVT-1 expression level was an independent risk factor for overall survival of colorectal cancer patients. CONCLUSION: PVT-1, which maps to 8q24, generates antiapoptotic activity in CRC, and abnormal expression of PVT-1 was a prognostic indicator for CRC patients.

PICT1 regulates TP53 via RPL11 and is involved in gastric cancer progression.

BACKGROUND: The TP53 pathway is frequently inactivated in human cancers. PICT1 (also known as GLTSCR2) is a novel regulator of the MDM2-TP53 pathway via its interaction with the ribosomal protein RPL11 in the nucleolus. However, the clinical significance of PICT1 in gastric cancer remains unknown. METHODS: To evaluate PICT1 function, we used shRNA to inhibit PICT1 expression in gastric cancer cells that expressed wild-type TP53. PICT1 expression and TP53 mutation status were quantified in 110 cases of primary gastric cancer to explore the impact of PICT1 expression levels on gastric cancer. RESULTS: Deficiency of PICT1 significantly impaired cell proliferation and colony formation via TP53-mediated cell cycle arrest. Following induction of PICT1 deficiency, RPL11 translocated out of the nucleolus. Of the 110 gastric cancer samples tested, 70 (63.6%) and 40 (36.4%) tumours expressed wild-type and mutant TP53, respectively. In gastric cancer patients with wild-type TP53 tumours, patients with relatively low PICT1 expression levels had a better prognosis compared with high expression level patients (P=0.046). CONCLUSION: The findings suggest that PICT1 has a crucial role in gastric cancer progression by regulating the MDM2-TP53 pathway through RPL11. Clinically, PICT1 expression is a novel prognostic parameter in gastric cancer patients with wild-type TP53 tumours.

Paired related homoeobox 1, a new EMT inducer, is involved in metastasis and poor prognosis in colorectal cancer.

BACKGROUND: Paired related homoeobox 1 (PRRX1) has been identified as a new epithelial-mesenchymal transition (EMT) inducer in breast cancer. However, the function of PRRX1 in colorectal cancer (CRC) has not been elucidated. METHODS: We utilised ectopic PRRX1-expressing cell lines to analyse the function of PRRX1 in CRC. The clinical significance of PRRX1 was also examined on three independent CRC case sets. RESULTS: PRRX1 induced EMT and the stem-like phenotype in CRC cells. In contrast to studies of breast cancer, abundant expression of PRRX1 was significantly associated with metastasis and poor prognosis in CRC. CONCLUSION: PRRX1 is an indicator of metastasis and poor prognosis in CRC cases. Further investigation is required to uncover the signalling network regulating PRRX1.

Sequential pancreaticoduodenectomy after living donor liver transplantation for cholangiocarcinoma.

Liver transplantation (LT) for patients with primary sclerosing cholangitis (PSC) is often contraindicated due to concomitant occurrence of cholangiocarcinoma (CC). Cases of simultaneous pancreaticoduodenectomy (PD) with LT have been sporadically reported; however, the applicability of such an invasive procedure to patients with CC has not been validated. We report here a case of sequential PD performed 44 days after a successful living donor liver transplantation (LDLT) using a left lobe graft. Although a clear pancreatic juice leakage through the drain persisted for days after surgery, the patient recovered from the complication and was discharged 32 days after the procedure. Currently, 1 year after LDLT, the patient is doing well with no evidence of recurrence. In conclusion, a sequential PD following LDLT is a safe and feasible option to treat CC complicating PSC. Long-term follow-up and accumulation of cases are necessary to evaluate the effectiveness of this procedure for this complicated disease.

Characterization of adipose tissue-derived cells isolated with the Celution system.

BACKGROUND: The therapeutic potential of using stem cells is tremendous. Mesenchymal stromal cells (MSC) have now been isolated in various tissues including bone marrow (BM), muscle, skin and adipose tissue. Among them, adipose tissue could be one of the most suitable cell sources for cell therapy, because of its easy accessibility, minimal morbidity and abundance of stem cells. The large numbers of stem cells in adipose tissue means that clinically relevant stem cell numbers could be extracted from the tissue, potentially eliminating the need for in vitro expansion. To utilize these characteristics of adipose tissue fully, Cytori Therapeutics Inc. has developed a closed system called Celution to isolate and concentrate stem cells and regenerative cells automatically from adipose tissue. METHODS: Adipose tissue-derived cells were isolated using the Celution system. The output from the Celution was characterized using multicolor FACS analysis with CD31, CD34, CD45, CD90, CD105 and CD146. The multidifferentiation potential of the cells was analyzed using adipogenic and osteogenic media. RESULTS: Our results showed that cells from the Celution are composed of heterogeneous cell populations including adipose-derived stem cells (ASC) (CD31- CD34+ CD45- CD90+ CD105- CD146-), endothelial (progenitor) cells (CD31+ CD34+ CD45- CD90+ CD105- CD146+) and vascular smooth muscle cells (CD31- CD34+ CD45- CD90+ CD105- CD146+). We also confirmed the output contains cells able to differentiate into adipogenic and osteogenic phenotypes. Our results show that cells isolated with the Celution and manually are equivalent. DISCUSSION: Cells from adipose tissue can be processed by Celution within the time frame of a single surgical procedure. This system could provide a 'real-time' treatment setting that is cost-effective and safe.

Biologic significance of angiopoietin-2 expression in human hepatocellular carcinoma.

Human hepatocellular carcinoma (HCC) is generally a highly vascular tumor, but the mechanisms of neovascularization that permit rapid growth have not been defined. Angiopoietins (Ang) recently have been identified as ligands for vascular endothelial-specific Tie2 receptor tyrosine kinase and may be important growth factors in the generation of new blood vessels. We investigated Ang expression in 23 samples of HCC and paired adjacent uninvolved liver samples to determine if these genes have a potential role in the growth and spread of this disease. The full coding sequence of a variant angiopoietin-2 (Ang2) cDNA was obtained from HCC specimens, and the biologic consequences of overexpression on tumor formation and hemorrhage were determined in an animal model system. Angiopoietin-1 (Ang1) was equally expressed in HCC and adjacent noncarcinomatous liver tissue. Surprisingly, Ang2 was found to be highly expressed only in tumor tissue. In addition, Ang2 was expressed in 10 of 12 hypervascular HCC, but only in 2 of 11 hypovascular HCC. Ectopic expression of Ang2 in nonexpressing HCC cells promotes the rapid development of human hepatomas and produces hemorrhage within tumors in nude mice. These results suggest a role for Ang2 in the neovascularization of HCC. This enhanced gene expression may contribute to the clinical hypervascular phenotype, as well as tumor formation and progression.

A novel variant of human Grb7 is associated with invasive esophageal carcinoma.

The cDNAs of a putative growth factor-bound (Grb) 7 signal transduction molecule and Grb7V novel splice variant were isolated from an invasive human esophageal carcinoma. Although both Grb7 isoforms share homology with the Mig-10 cell migration gene, the Grb7V isoform lacks 88 base pairs in the C terminus; the resultant frame shift leads to substitution of an SH2 domain with a short hydrophobic sequence. The wild-type Grb7 protein, but not the Grb7V isoform, is rapidly tyrosyl phosphorylated in response to EGF stimulation in esophageal carcinoma cells. Analysis of human esophageal tumor tissues and regional lymph nodes with metastases revealed that Grb7V was expressed in 40% of Grb7-positive esophageal carcinomas. More importantly, Grb7V expression was enhanced after metastatic spread to lymph nodes as compared to the original tumor tissues. Finally, transfection of an antisense Grb7 RNA expression construct lowered endogenous Grb7 protein levels and suppressed the invasive phenotype exhibited by esophageal carcinoma cells. These findings suggest that Grb7 isoforms are involved in cell invasion and metastatic progression of human esophageal carcinomas.

Expression and differential intracellular localization of two major forms of human 8-oxoguanine DNA glycosylase encoded by alternatively spliced OGG1 mRNAs.

We identified seven alternatively spliced forms of human 8-oxoguanine DNA glycosylase (OGG1) mRNAs, classified into two types based on their last exons (type 1 with exon 7: 1a and 1b; type 2 with exon 8: 2a to 2e). Types 1a and 2a mRNAs are major in human tissues. Seven mRNAs are expected to encode different polypeptides (OGG1-1a to 2e) that share their N terminus with the common mitochondrial targeting signal, and each possesses a unique C terminus. A 36-kDa polypeptide, corresponding to OGG1-1a recognized only by antibodies against the region containing helix-hairpin-helix-PVD motif, was copurified from the nuclear extract with an activity introducing a nick into DNA containing 8-oxoguanine. A 40-kDa polypeptide corresponding to a processed form of OGG1-2a was detected in their mitochondria using antibodies against its C terminus. Electron microscopic immunocytochemistry and subfractionation of the mitochondria revealed that OGG1-2a locates on the inner membrane of mitochondria. Deletion mutant analyses revealed that the unique C terminus of OGG1-2a and its mitochondrial targeting signal are essential for mitochondrial localization and that nuclear localization of OGG1-1a depends on the NLS at its C terminus.

Increased hyperthermic response with prostaglandin E1 in VX2 liver carcinoma in rabbits.

Most studies examining the potential of vasoactive drugs to selectively reduce the blood flow in a tumor and to enhance the thermal response to hyperthermia have used tumors growing in muscle tissues. We investigated the effect of prostaglandin E1 on a VX2 liver carcinoma in 95 female Japanese white rabbits. During continuous 20-minute intravenous infusions of prostaglandin E1 at doses of 1, 3, and 5 micrograms/kg per minute in rabbits with this liver tumor, the mean arterial blood pressure decreased to 81%, 74%, and 51% of initial levels, respectively. In the tumor, regional blood flow was 86%, 70%, and 56% of initial levels, respectively; in the adjacent liver tissue, it was 149%, 110%, and 86% of initial levels, respectively. The tumor and adjacent liver tissues were heated by a microwave generator, and the liver tissue was kept at 42.0 degrees C. The average temperature at the center of the tumor, which was 43.0 degrees C in the absence of prostaglandin E1, increased to 44.3 degrees C, 44.3 degrees C, and 44.2 degrees C when doses of 1, 3, and 5 micrograms/kg per minute were given, respectively. The therapeutic effect was determined on the basis of the tumor growth ratio (geometric tumor volume 7 days after treatment/volume at start of treatment). Hyperthermia alone resulted in a small reduction in the tumor growth ratio--from the control value of 11.82 to a value of 9.03. Hyperthermia combined with prostaglandin E1 led to an augmented reduction in tumor growth ratio (4.28, 4.70, and 4.79 during 1, 3, and 5 micrograms/kg per minute, respectively), compared with findings with hyperthermia alone. These results indicate that prostaglandin E1 reduces tumor blood flow, elevates tumor temperature during hyperthermia, and retards tumor growth after local heat treatment. For these reasons, prostaglandin E1 may be an effective adjuvant drug in clinical studies of hyperthermia in liver tumor.

Enhancement of esophageal carcinogenesis induced in rats by N-amyl-N-methylnitrosamine in the presence of 12-O-tetradecanoylphorbol-13-acetate.

The effects of 12-O-tetradecanoylphorbol-13-acetate (TPA), a tumor-promoting phorbol diester, were determined with regard to the induction of esophageal cancer in Wistar rats following a low-dose initial administration of the esophageal carcinogen N-amyl-N-methylnitrosamine [(AMN) CAS: 13256-07-0]. The induction of esophageal cancer was enhanced by TPA given in drinking water after AMN administration; i.e., the incidence of developing esophageal cancers and the multiplicity (number of esophageal cancers per rat) were significantly higher in groups given TPA solution orally after an oral administration of AMN than in those given the AMN solution alone. The enhancement of carcinogenesis with TPA was not affected by the interval between the administration of AMN and the administration of TPA. However, pretreatment with TPA before AMN administration did not enhance the induction of esophageal cancer. Neoplasms were not detected in groups given only TPA or tap water. Because this approach is similar to the phenomenon of two-stage carcinogenesis in the skin, it should provide a meaningful experimental model for studying two-stage carcinogenesis in the esophagus.

Immunohistochemical evidence of urokinase-type plasminogen activator in primary and metastatic tumors of pulmonary adenocarcinoma.

The urokinase-type plasminogen activator (u-PA) was used to study 96 cases of lung adenocarcinoma and 49 cases of lymph node metastatic adenocarcinoma. We made use of the immunohistochemistry of paraffinized samples. u-PA was detected in the cytoplasm of tumor cells, and the number of positive cells was higher in patients with T2 or T3 than in those with T1 disease (P less than 0.01). These u-PA-positive tumor cells were more frequent in patients with N2 than in those with N1 disease (P less than 0.01). Such cells were also detected in patients with N1 rather than N0 disease (P less than 0.01). When we compared the frequency of u-PA-positive tumor cells in metastatic lesions with that in primary ones, the former tended to be higher. On the other hand, the frequency of u-PA-positive cells in primary tumors of patients with a recurrence was higher than in those with no recurrence. Thus, u-PA is an important prognostic indicator associated with tumor growth and lymph node spread. If u-PA is detected in a tumor, a recurrence can be expected.

Hyperthermia, tissue microcirculation, and temporarily increased thermosensitivity in VX2 carcinoma in rabbit liver.

The role of microcirculatory factors within and around liver tumors after heat treatment was investigated in a rabbit model of liver cancer (VX2 carcinoma). As a physiological factor of the microenvironment, regional blood flow (RBF) was measured by the hydrogen clearance method, and a histopathological study was done. Local hyperthermia was administered directly to the liver tumor via a 915-MHz microwave. Hyperthermia produced a temporary reduction of RBF in both the tumor and the surrounding normal liver tissues, and the histopathology revealed congestion, petechiae, and thrombosis. After hyperthermia at 43.0 degrees C for 20 min, RBF in the tumor rapidly decreased to a minimum of 40% of the control level during 0-12 h after the treatment and increased gradually to the pretreatment level at 2 days. RBF in the normal liver also decreased rapidly after hyperthermia, to a minimum of 30% of the pretreatment level, 1-12 h after treatment. In the case of treatment at 42.5 degrees C for 20 min, RBF in the tumor also rapidly decreased to a minimum of 40% of the control level, at 4 h after the treatment, and recovery was within 2 days. However, RBF in the surrounding normal liver decreased to 80% of the control level, at 2 h after the treatment, and then increased more rapidly to reach levels seen in the controls. Thus, the latter condition of heat treatment was considered to be favorable for therapeutic gain. Based on the results of these sequential microcirculatory changes, the effects of continuous and intermittent hyperthermia were studied in groups given various treatments. In a group treated with intermittent hyperthermia at 4-h intervals, the antitumor effects determined by tumor growth retardation were significantly greater, as compared with findings in the group given treatment without an interval and that given at a 24-h interval (P less than 0.001). In the tumor at 4 h after hyperthermia, the increased thermosensitivity was considered to surpass the developing thermotolerance. Thus, the antitumor effect of hyperthermia in vivo greatly depends on the microcirculation. The most efficacious mode for application of hyperthermia must be vigorously examined if a clinical relevance is to be gained.

Cathepsin B expression and laminin degradation as factors influencing prognosis of surgically treated patients with lung adenocarcinoma.

We examined, immunohistochemically, tissues from primary lung adenocarcinomas. In 142 tumors, the mean overall labeling percentage of cathepsin B was 26.5 +/- 22.3 (SD). The mean labeling percentage of cathepsin B in cases with stage I disease was lower than that in cases with stages IIIA, IIIB, or IV disease (P < 0.05). Of the 115 tumors examined for laminin-positive basement membranes, 54 (47%) had a continuous pattern and 61 (53%) had a discontinuous pattern. The mean labeling percentage of cathepsin B was 35.0 +/- 24.2 in tumors with a discontinuous pattern, compared with the 21.9 +/- 16.9 in those with a continuous pattern (P < 0.01). The overall 5-year survival rates of patients with high and low cathepsin B expressions were 26% and 77%, respectively (P < 0.01), including 45% and 94% for patients with stage I disease, respectively (P < 0.01), and 15% and 60% for those with stage IIIB disease, respectively (P < 0.05). Multivariate analysis using the Cox life table regression model showed cathepsin B to be a significantly independent factor associated with death due to the disease. We conclude from this study that tumors with a discontinuous pattern of laminin have a higher percentage of cathepsin B, and the survival rate was poor for patients with a high expression of cathepsin B. Thus, cathepsin B may be useful in assessing prognosis in lung adenocarcinoma.

Proliferating cell nuclear antigen expression and argyrophilic nucleolar organizer regions as factors influencing prognosis of surgically treated lung cancer patients.

Cell proliferation in 211 primary non-small cell lung carcinomas was assessed by using an immunostaining of proliferating cell nuclear antigen (PCNA) and a silver staining of argyrophilic nucleolar organizer region (Ag-NOR). More than 5% PCNA positive cells was designated PCNA(+), and less than 5% was PCNA(-). A mean number or more of the Ag-NOR was a high Ag-NOR count, and less than the mean number was a low Ag-NOR count. The proportion of the tumors with PCNA(+) and high Ag-NOR counts showed an increase in patients in an advanced stage of the disease (P < 0.05). In 125 patients with stage I disease, the 5-year survival rate was 20% in patients with PCNA(+) and high Ag-NOR counts, compared with 47% in those with either PCNA(+) or high Ag-NOR counts and 76% in those with PCNA(-) and low Ag-NOR counts (P < 0.05). Our data suggest that the tumors with PCNA(+) and high Ag-NOR counts have a high proliferative activity. The combination analysis of PCNA and Ag-NOR may be useful in assessing prognosis in lung cancer, even in stage I disease.