[A case of effective chemoradiotherapy using docetaxel and nedaplatin for recurrent anal canal squamous cell carcinoma].

69-year-old woman underwent resection of a tumor diagnosed as squamous cell carcinoma of the anal canal. After 4 years and 5 months, computed tomography(CT)showed abdominal and pelvic lymph node swelling. Chemotherapy consisting of biweekly docetaxel(35mg/m2)+nedaplatin(35mg/m2)achieved a partial response. After 20 cycles of chemotherapy, the patient was treated with radiotherapy because of a pelvic lymph node recurrence. Since then, no recurrence has occurred for 16 months. The adverse event was Grade 2 in leucopenia and neutropenia. This case suggested that chemoradiotherapy consisting of docetaxel +nedaplatin may be effective and safe for treating anal canal squamous cell carcinoma.

Tumorigenesis of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), but not enhancing effects of concomitant high-fat diet, on lung carcinogenesis in female A/J mice.

It has been reported that 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) induces liver tumors and to a lesser extent lung lesions, lymphomas and leukemias in CDF(1) mice. Since a number of case control studies have pointed to a positive association between fat consumption and lung cancer, we examined the lung carcinogenic potential of MeIQx treatment concomitant with a high-fat diet using female A/J mice. Groups 1 and 2 were fed a diet supplemented with MeIQx at a concentration of 600 ppm. Groups 1 and 3 received a diet containing 20% corn oil and group 4 was fed the basal diet alone. After 1 week, 10 mice in each group were sacrificed for measurement of cytochrome P450 (CYP)1A2 mRNA in the liver and lung. The remaining mice were maintained on their respective diets until termination, 32 weeks after the initial MeIQx treatment, when lung proliferative lesions were analyzed. The incidences and multiplicities of hyperplasias and adenomas in MeIQx-treated groups (groups 1 and 2) were significantly higher than in the groups without MeIQx treatment, with a significant increase in the incidences and multiplicities of adenomas + carcinomas, as well as hyperplasia + adenomas + carcinomas (lung proliferative lesions). Lung carcinomas were observed in 1 mouse in each of the MeIQx-treated groups. However, the high-fat diet (groups 1 and 3) did not affect the incidences or multiplicities of lung proliferative lesions. Expression levels of CYP1A2 mRNA after MeIQx treatment significantly increased >3-fold in livers, but no significant change was noted in the lungs, where levels were very low at 1/210 and 1/923 the values for livers. In conclusion, following a 32-week period, we confirmed the lung tumorigenic potential of MeIQx which possibly occurs due to proximate carcinogens activated by CYP1A2 in the liver. However, we failed to detect any influence of a high-fat diet.

8-Methoxypsoralen, a potent human CYP2A6 inhibitor, inhibits lung adenocarcinoma development induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in female A/J mice.

Previously, we demonstrated that 8-methoxypsoralen (methoxsalen), a potent human cytochrome P450 2A6 (CYP2A6) inhibitor, strongly suppresses lung adenoma induction by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in female A/J mice. In the present study, we examined the inhibitory effects of methoxsalen on the development of lung adenocarcinomas, as well as on adenomas and alveolar hyperplasia. Female A/J mice were treated with methoxsalen at doses of 12.5 or 1.25 mg/kg body weight, administered by stomach tube once daily for 3 days. One hour after the final treatment, NNK was injected i.p. at a dose of 2 mg/mouse. The experiments were terminated 52 weeks after the first methoxsalen treatment, and lung adenomas and adenocarcinomas were analyzed histopathologically. Pretreatment with methoxsalen significantly reduced the incidence of adenocarcinomas from 94.7 to 46.7% (12.5 mg/kg) and 44.4% (1.25 mg/kg), and their tumor multiplicity from 4.68 to 0.87 (12.5 mg/kg) and 0.61 (1.25 mg/kg) tumors/mouse. The tumor multiplicity of adenomas and adenocarcinomas in the methoxsalen-treated groups was significantly reduced from 12.47 to 5.67 (12.5 mg/kg) and 4.28 (1.25 mg/kg) tumors/mouse. Approximately 60% of the adenocarcinomas arose within adenomas. In comparing the methoxsalen + NNK and NNK alone groups, there was no significant difference in the frequency of such compound lesions, indicating that pretreatment with methoxsalen did not suppress the eventual progression of adenomas to adenocarcinomas. These results clearly demonstrate that methoxsalen, a potent human CYP2A6 inhibitor, inhibits not only lung adenoma but also adenocarcinoma development.

Enhancing effects of a high fat diet on 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline-induced lung tumorigenesis in female A/J mice.

Both heterocyclic amines and a high fat diet are associated with an increased risk of cancer in many organs. Female A/J mice were fed a diet supplemented with 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and a high fat diet to test for the development of lung tumors. In experiment 1, the mice were divided into 6 groups. Groups 1, 2, 3 and 4 were fed a diet supplemented with MeIQx at a concentration of 600?ppm for 0-12 weeks. A high fat diet containing 20% corn oil was given to Groups 1 and 5 for 0-32 weeks, Group?2 for 12-32 weeks and Group 3 for 0-12 weeks. Group 6 was fed a basal diet without supplements. MeIQx-treated groups (Groups?1, 2, 3 and 4) showed a significant increase in macroscopic and microscopic lung nodules compared with the control (Group 6). Areas of adenomas were increased dependent on the duration of exposure to the high fat diet. In experiment 2, Group 1 mice were fed MeIQx and a high fat diet, Group?2 a MeIQx alone diet, Group 3 a high fat alone diet, and Group?4 a basal diet without supplements. CYP1A2 mRNA in the liver was significantly decreased by a high fat diet (Group?3). The MeIQx alone group (Group 2) showed a tendency towards increased CYP1A2 expression, which was partially reduced in the MeIQx + high fat-treated group (Group 1). In the lungs, CYP1A2 mRNA expression was at an extremely low level, with no intergroup differences. In conclusion, MeIQx exerts tumorigenic potential in the lungs, and a high fat diet increases the size of induced lesions. The expression level of CYP1A2 in relation to MeIQx and a high fat diet may be associated with lung carcinogenesis.

Establishment of a bioassay model for lung cancer chemoprevention initiated with 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in female A/J mice.

AIMS: In order to prevent lung cancer development in people at high risk, identification of chemopreventive agents may be important. The present study was conducted to establish a bioassay model for this purpose. In particular, the time course of 4-(methylnitrosamno)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumor development was examined to determine the most appropriate shortest period to assess effects of test agents, with 8-methoxypsoralen (8-MOP) as a typical example. METHODS: A total of 124 mice were separated into two groups (Group A: 60 mice, Group B: 64 mice), pretreated with 100ppm 8-MOP (Group A) or basal diet (Group B) for 3 days before receiving single doses of NNK (2mg/0.1ml saline/mouse i.p.) on days 0 and 7. Subgroups of 15 mice of each group were then sacrificed after 8, 10, 12, and 16 weeks. RESULTS: Microscopically, the earliest time point when significant differences in data for hyperplasia, adenoma and hyperplasia and adenoma could be detected was 12 weeks. A trend was noted for 8-MOP to reduce adenomas to a greater extent than hyperplasia. DISCUSSION: In conclusion, the results of this study showed that the double i.p. treatment with NNK and 12 weeks duration are effective for detection of lung cancer chemoprevention in our A/J mouse lung tumorigenesis model.

Induction of multiple granulomas in the liver with severe hepatocyte damage by montan wax, a natural food additive, in a 90-day toxicity study in F344 rats.

Montan wax is a mineral wax extracted from lignite type coal. It has been registered as a food additive in Japan though there have been no reports of toxicological evaluation, mainly due to the fact that it is considered a natural product. As part of a general safety assessment of montan wax, we have performed a 90-day toxicity study in Fisher 344 (F344) rats. Groups of 10 males and 10 females were given the material at dose levels of 0 (Group 1), 0.56 (Group 2), 1.67 (Group 3), or 5% (Group 4) in the diet for 90 days. During the experiment, there were no remarkable changes in general conditions and no deaths occurred in any group. On hematological examination, Hb, Ht, MCV and MCH were significantly decreased and WBC was significantly increased in all treated rats. On serum biochemical examination, AST and ALT were found to be elevated more than four fold in all treated groups as compared to the respective control group values in both sexes. Furthermore, relative organ weights for the liver, spleen, lung and kidneys were increased in all treated groups of both sexes. Histopathological examination revealed diffuse multiple granulomas in the livers with severe hepatocyte damage and lymphocytic infiltration. Granulomatous lesions were also apparent in the mesenteric lymph nodes in all treated males and females. These findings clearly demonstrate that montan wax, at doses of more than 0.56% in the diet, induces multiple granulomas with severe inflammation in the liver. Because pathological, hematological and serum biochemical changes were observed in the lowest dose group, a no-observed-adverse-effect level (NOAEL) could not be determined in the present study.

Post-initiation chemopreventive effects of dietary bovine lactoferrin on 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced lung tumorigenesis in female A/J mice.

We investigated the effects of bovine LF (bLF) on different phases of NNK-induced lung tumorigenesis in A/J mice. Mice were orally administered 0.02, 0.2 and 2% bLF during the initiation phase, and 2% bLF during the whole tumorigenesis phase or post-initiation phase. Administered bLF during the post-initiation phase showed significant reduction of macroscopical lung nodules, and immunohistochemically decreased expression levels of cell proliferation marker and increased expression levels of apoptosis marker in lung proliferative lesions. bLF might inhibit NNK-induced mouse lung tumorigenesis, only when given limited to the post-initiation phase, through modification of cell proliferation and/or apoptosis.

Bioassay by intratracheal instillation for detection of lung toxicity due to fine particles in F344 male rats.

We have established and documented an in vivo bioassay for detection of hazards with intratracheally instilled fine particles, which can be used for risk assessment of toxicity of materials inhaled into deep lung tissue of humans (Yokohira et al. Establishment of a bioassay system for detection of lung toxicity due to fine particle instillation: sequential histopathological changes with acute and subacute lung damage due to intratracheal instillation of quartz in F344 male rats. J Toxicol Pathol 2005;18:13-8). For validation we here examined toxicity of fine particles from quartz, hydrotalcite, potassium octatitanate, palladium oxide and carbon black with this bioassay. A total of 108, 10-week-old F344/DuCrj male rats were randomly divided into 8 groups. Groups 1 to 5 underwent intratracheal instillation of the 5 test particles (4 mg/rat) suspended in 0.2 ml vehicle (saline or 10% propylene glycol and 1% sodium carboxymethyl cellulose in saline: PG-CMC) with a specially designed aerolizer, and subgroups of 7 rats were killed on Days 1 and 28 thereafter. Groups 6 and 7 similarly were exposed to saline and PG-CMC, respectively, as vehicle controls, while group 8 was maintained untreated. Using histopathological changes and immunohistochemically assessed bromodeoxyuridine (BrdU) labeling indices, inducible nitric oxide synthase (iNOS) and matrix metalloproteinase-3 (MMP-3) levels as end points, the quartz treated group exhibited high toxicity, while the values for the other particle-treated groups pointed to only slight effects. Although additional efforts are needed to establish advantages and disadvantages with our bioassay, models featuring intratracheal instillation clearly can be useful for detection of acute or subacute lung toxicity due to inhaled fine particles by using histopathological scoring and markers like BrdU and iNOS for screening purposes in short-term studies.

Dose dependent inhibitory effects of dietary 8-methoxypsoralen on NNK-induced lung tumorigenesis in female A/J mice.

We have reported that pretreatment by stomach tube with 8-methoxypsoralen (methoxsalen; 8-MOP), a potent human CYP2A6 inhibitor, strongly suppresses lung tumorigenesis by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in female A/J mice (Cancer Res. 2003). Here, we examined inhibitory effects with administration in the diet. When the mice were 7 weeks of age, they received dietary supplementation with 8-MOP at concentrations of 1, 10 or 100 ppm for 3 days prior to a single dose of NNK (2mg/0.1 ml saline/mouse, i.p.) or an equal volume of saline (vehicle control). The experiment was terminated 16 weeks after the first 8-MOP treatment and lung proliferative lesions were analyzed. The incidences and multiplicities in the 8-MOP 100 ppm-treated group were significantly reduced as compared with values for the NNK alone group (P<0.001). Multiplicities of NNK-induced lung proliferative lesions were also reduced in a dose dependent manner (Spearman rank correlation coefficient; rho=-0.806, correction P<0.0001). Mouse CYP2A4 and CYP2A5 differ from each other only 11 amino acids, and are closely related to the human CYP2A6. One hour after the last of three daily doses of 8-MOP (0.5, 5 or 50mg/kg body weight in 0.2 ml corn oil, given by stomach tube) or an equal volume of corn oil (vehicle control), given to the mice at 7 weeks of age, isolation of lung and liver RNAs demonstrated no effects on CYP2A4 and CYP2A5 mRNA levels with 8-MOP. In conclusion, the results of this study showed that clear dose response inhibitory effects of 8-MOP on NNK-induced lung tumorigenesis in female A/J mice fed diets containing 8-MOP, due to inhibition of enzyme activity of CYP2A4 and CYP2A5, rather than their gene expression.

Epithelioid malignant peripheral nerve sheath tumor. Report of a case with inflammatory infiltration.

The epithelioid malignant peripheral nerve sheath tumor (EMPNST) is a rare sarcoma originating from the supportive non-neuronal components of peripheral nerves. Our patient was a 75-year-old Japanese man who presented with complaints about pain and a mass in the left thigh. Characteristic histopathological features were large epithelioid-like cells closely resembling a malignant melanoma or another type of soft tissue tumor. Notable infiltration of neutrophils in the tumor was seen. Immunohistochemically, the tumor cells proved positive for S-100, NSE, GFAP, MBP, chromogranin A and synaptophysin, and negative for CEA, keratin, HMB-45, G-CSF, and GM-CSF. Tumor-related inflammatory infiltration may be caused by an autonomous production of some cytokines. However, these tumor cells were negative for G-CSF and GM-CSF so that the mechanism triggering inflammatory infiltration is unclear. Electron microscopy revealed the presence of an extracellular basal lamina, intermediate cell junctions, and numerous dense-cored granules in the cytoplasm. These findings suggested a schwannian derivation, consistent with the diagnosis of EMPNST. There have been reports on S-100 positivity and HMB-45 negativity of this tumor type, but to the best of our knowledge, this is the first description of an EMPNST positive for MBP, chromogranin A, and synaptophisin. Where unequivocal features are lacking, these markers might be useful for differential diagnosis.

Mechanisms of chemopreventive effects of 8-methoxypsoralen against 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced mouse lung adenomas.

Recently we reported that the occurrence of lung adenoma caused by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was completely prevented by pretreatment of female A/J mice with 8-methoxypsoralen, a potent inhibitor of cytochrome P450 (P450 or CYP) 2A [Takeuchi et al. (2003) Cancer Res., 63, 7581-7583]. Thus, the aim of this study was to confirm that 8-methoxypsoralen exhibits chemopreventive effects by inhibiting CYP2A in the mouse lung. The involvement of CYP2A in the metabolic activation of NNK in the lung was first evidenced by the fact that the mutagenic activation of NNK by mouse lung microsomes was inhibited by 8-methoxypsoralen, coumarin and antibodies to rat CYP2A1. Supporting this, the mutagenic activation of NNK was efficiently catalyzed by mouse CYP2A4 and CYP2A5 co-expressed with NADPH-P450 reductase in a genetically engineered Salmonella typhimurium YG7108. The expression of mRNA for CYP2A5, but not for CYP2A4 or CYP2A12, in the mouse lung was proven by reverse transcriptase-polymerase chain reaction, probably indicating that CYP2A5 present in the mouse lung was involved in the metabolic activation of NNK. In accordance with these in vitro data, treatment of gpt delta transgenic mice with 8-methoxypsoralen prior to NNK completely inhibited the mutation of the gpt delta gene. The in vivo chemopreventive effects of 8-methoxypsoralen towards NNK-induced adenoma was seen only when the agent was given to female A/J mice prior to, but not posterior to, NNK, lending support to the idea that NNK is activated by CYP2A5 in the mouse lung as an initial step to cause adenoma. The inhibition by 8-methoxypsoralen of NNK-induced adenoma was seen in a dose-dependent manner: the dose to show apparent 50% suppression was calculated to be 1.0 mg/kg. To our surprise, CYP2A protein(s) was expressed in the lesion of NNK-induced lung adenomas, probably suggesting that 8-methoxypsoralen could inhibit the possible occurrence of further mutation of the adenoma cells induced by NNK. Based on these lines of evidence, we propose that 8-methoxypsoralen inhibits the CYP2A5-mediated metabolic activation of NNK in the mouse lung, leading to the prevention of NNK-induced adenoma.

Lack of significant modifying effect of arctiin on prostate carcinogenesis in probasin/SV40 T antigen transgenic rats.

Arctiin, a plant lignan that can be extracted from the Arctium lappa (burdock) seeds, is a possible environmental endocrine disruptor compounds and have been shown to influence sex hormone metabolism as well as protein synthesis, steroid biosynthesis. Modifying effects of arctiin on prostate carcinogenesis in probasin/SV 40 T antigen (Tag) transgenic (TG) rats were examined. A total of 64 male TG rats, 6 weeks old, were randomly divided to three experimental groups (soybean free Oriental MF diet with 0.1, 0.02, or 0.004% arctiin) and a control group (soybean free Oriental MF diet). Animals were killed at the end of week 18. Histopathological evaluation of prostate revealed that all the rats in any group developed adenocarcinoma in dorsolateral lobe of prostate, except two rats in 0.1% arctiin treated and one rat in 0.002% arctiin treated groups without prostate adenocarcinoma development. However, there were no definite treatment-related changes with statistical significance in all parameters for prostate carcinomas measured in this experiment. These results indicated that arctiin might not exert significant modifying effect on prostate carcinogenesis in SV 40 Tag TG rats at least under the present experiment.

Inhibition of prostate carcinogenesis in probasin/SV40 T antigen transgenic rats by raloxifene, an antiestrogen with anti-androgen action, but not nimesulide, a selective cyclooxygenase-2 inhibitor.

The chemopreventive efficacies of raloxifene and nimesulide, an anti-estrogen but with anti-androgen action and a cyclooxygenase-2 (COX-2) selective inhibitor, respectively, were evaluated in probasin/SV40 T antigen (Tag) transgenic (TG) rats. The treatment groups were placebo, nimesulide (400 p.p.m. in basal diet p.o.), raloxifene (slow-release pellets implanted s.c., 5 mg/kg/day), raloxifene (5 mg/kg/day) plus nimesulide (400 p.p.m.), and raloxifene (10 mg/kg/day) plus nimesulide (400 p.p.m.). Animals were killed at 17 weeks of age, and prostate tissues were harvested and weighed by lobes. Tissues were evaluated by histology, immunohistochemistry, and western blot analyses and blood was collected to measure the testosterone levels. All the animals in the placebo group had tumors in each lobe compared with only 43% each in the dorsolateral (DLP) and anterior prostate (AP) of the animals treated with raloxifene (10 mg/kg/day) plus nimesulide. The total prostate weights and adenocarcinoma portions were significantly reduced in the three raloxifene-treated groups, whereas atrophic glands were increased. There were no significant differences between the nimesulide alone and placebo groups or between the raloxifene (5 mg/kg/day) alone and raloxifene (5 mg/kg/day) plus nimesulide group, suggesting a lack of cancer preventive effects of the COX-2 inhibitor in this animal model. PCNA positive rates in ventral prostate (VP) and DLP, and androgen receptor (AR) levels in VP were significantly reduced in the three raloxifene-treated groups. Furthermore, circulating testosterone was decreased after raloxifene (10 mg/kg/day) plus nimesulide treatment. These results demonstrate that raloxifene, but not nimesulide, inhibits prostate carcinogenesis in SV40 Tag TG rats associated with a decline in circulating testosterone levels and a loss of AR expression, as well as an inhibition of cell proliferation.

Pretreatment with 8-methoxypsoralen, a potent human CYP2A6 inhibitor, strongly inhibits lung tumorigenesis induced by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in female A/J mice.

Human CYP2A6 has been recognized as being involved in the mutagenic activation of promutagens such as the tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Methoxsalen (8-methoxypsoralen) was reported to inhibit CYP2A6. In the present study, the inhibitory effects of methoxsalen on NNK-induced lung tumorigenesis in female A/J mice were examined. Female A/J mice were treated with methoxsalen at doses of 50 or 12.5 mg/kg body weight, given by stomach tube, daily for 3 days. One h after the final treatment, NNK was injected i.p. at a dose of 2 mg/mouse. The experiments were terminated 16 weeks after the first methoxsalen treatment, and lung adenomas were analyzed. Pretreatment of methoxsalen significantly reduced tumor incidence from 93.8% to 16.7% (50 mg/kg) and 20.0% (12.5 mg/kg), and tumor multiplicity from 5.97 to 0.23 (50 mg/kg) and 0.25 (12.5 mg/kg) tumors/mouse. These results clearly demonstrated that methoxsalen, a potent human CYP2A6 inhibitor, is a strong chemopreventive agent against NNK-induction of lung tumorigenesis.

Loss of p57KIP2 is associated with colorectal carcinogenesis.

The expression and significance of p57KIP2, an important inhibitor of the cell cycle, remain unclear during carcinogenesis and during late metastasis to lymph nodes of tumors. To detail changes of p57KIP2 during colorectal carcinogenesis and during late metastasis to lymph nodes, p57KIP2, cyclin A, cyclin B1, cyclin E, CDK2, and Ki67 were immunohistochemically investigated in 22 specimens of normal mucosa, 62 of adenomas, 17 of carcinomas in adenomas, 189 of primary carcinomas, and 23 of lymph node metastases. Situated in nuclei, p57KIP2 expression increased significantly from normal mucosa to adenomas (p=0.0068), from mild through moderate to severe dysplasia in adenomas (p=0.0132). It significantly decreased from adenomas to unpaired primary carcinomas (p=0.0112) and from peripheral adenomas to paired central carcinomas (p=0.0018), but remained unchanged when primary carcinomas metastasized to lymph nodes (p=0.3401). p57KIP2 expression was not correlated with clinicopathological indices, but the patients having tumors without p57KIP2 tended to show a poor prognosis (p=0.0674). High p57KIP2 was significantly correlated with increased cyclin A (p=0.0007), elevated cyclin B1 (p=0.0007), reduced CDK2 (p=0.0021), and increased Ki67 (p=0.0013) in adenomas. Thus, loss of p57KIP2 expression appears associated with colorectal carcinogenesis.

Cyclin B1, unlike cyclin G1, increases significantly during colorectal carcinogenesis and during later metastasis to lymph nodes.

In collaboration with p53, cyclins B1 and G1 regulate the G2/M transition, a key checkpoint in the active cell cycle, which can be monitored by Ki67. However, the cyclin B1 expression remains unclear during colorectal carcinogenesis and during later metastasis to lymph nodes, and cyclin G1 expression is not clear in colorectal tumors. To clarify the variations of the two cyclins in colorectal tumors, cyclin B1, cyclin G1, p53, and Ki67 were immunohistochemically stained in 22 normal mucosa, 62 adenomas, 17 carcinomas in adenomas, 194 primary carcinomas, and 21 lymph node metastases; and the two cyclins were examined by Western blot in other 10 pairs of normal mucosa and primary carcinomas. Located in cytoplasms, nuclei or both, cyclin B1 expression increased significantly from normal mucosa through adenomas to primary carcinomas, from adenomas with mild dysplasia through those with moderate to those with severe, from peripheral adenomas to their central carcinomas, and from primary to metastatic foci. These increased expressions were confirmed by Western blot. Cyclin B1 expression, however, declined significantly in primary carcinomas showing large size, mucinous type, deep invasion, or short postoperative-patient-survival time. High cyclin B1 was linked to high p53 in adenomas, and to high Ki67 in adenomas and primary carcinomas. In contrast, found limited to nuclei, cyclin G1 expression did not vary significantly from normal mucosa through to metastatic carcinomas, and was not associated with clinicopathological parameters, p53 or Ki67. The unchanged expressions were confirmed by Western blot. Thus, increased cyclin B1, but not cyclin G1, may promote colorectal carcinogenesis and later metastasis to lymph nodes.