Expanding Roles of the E2F-RB-p53 Pathway in Tumor Suppression

The transcription factor E2F links the RB pathway to the p53 pathway upon loss of function of pRB, thereby playing a pivotal role in the suppression of tumorigenesis. E2F fulfills a major role in cell proliferation by controlling a variety of growth-associated genes. The activity of E2F is controlled by the tumor suppressor pRB, which binds to E2F and actively suppresses target gene expression, thereby restraining cell proliferation. Signaling pathways originating from growth stimulative and growth suppressive signals converge on pRB (the RB pathway) to regulate E2F activity. In most cancers, the function of pRB is compromised by oncogenic mutations, and E2F activity is enhanced, thereby facilitating cell proliferation to promote tumorigenesis. Upon such events, E2F activates the Arf tumor suppressor gene, leading to activation of the tumor suppressor p53 to protect cells from tumorigenesis. ARF inactivates MDM2, which facilitates degradation of p53 through proteasome by ubiquitination (the p53 pathway). P53 suppresses tumorigenesis by inducing cellular senescence or apoptosis. Hence, in almost all cancers, the p53 pathway is also disabled. Here we will introduce the canonical functions of the RB-E2F-p53 pathway first and then the non-classical functions of each component, which may be relevant to cancer biology.

Targeting cis-regulatory elements of FOXO family is a novel therapeutic strategy for induction of leukemia cell differentiation

Differentiation therapy has been proposed as a promising therapeutic strategy for acute myeloid leukemia (AML); thus, the development of more versatile methodologies that are applicable to a wide range of AML subtypes is desired. Although the FOXOs transcription factor represents a promising drug target for differentiation therapy, the efficacy of FOXO inhibitors is limited in vivo. Here, we show that pharmacological inhibition of a common cis-regulatory element of forkhead box O (FOXO) family members successfully induced cell differentiation in various AML cell lines. Through gene expression profiling and differentiation marker-based CRISPR/Cas9 screening, we identified TRIB1, a complement of the COP1 ubiquitin ligase complex, as a functional FOXO downstream gene maintaining an undifferentiated status. TRIB1 is direct target of FOXO3 and the FOXO-binding cis-regulatory element in the TRIB1 promoter, referred to as the FOXO-responsive element in the TRIB1 promoter (FRE-T), played a critical role in differentiation blockade. Thus, we designed a DNA-binding pharmacological inhibitor of the FOXO-FRE-T interface using pyrrole-imidazole polyamides (PIPs) that specifically bind to FRE-T (FRE-PIPs). The FRE-PIPs conjugated to chlorambucil (FRE-chb) inhibited transcription of TRIB1, causing differentiation in various AML cell lines. FRE-chb suppressed the formation of colonies derived from AML cell lines but not from normal counterparts. Administration of FRE-chb inhibited tumor progression in vivo without remarkable adverse effects. In conclusion, targeting cis-regulatory elements of the FOXO family is a promising therapeutic strategy that induces AML cell differentiation.

RHEB is a potential therapeutic target in T cell acute lymphoblastic leukemia

T cell acute lymphoblastic leukemia (T-ALL) is an aggressive malignancy of immature T lymphocytes. Although various therapeutic approaches have been developed, refractoriness of chemotherapy and relapse cause a poor prognosis of the disease and further therapeutic strategies are required. Here, we report that Ras homolog enriched in brain (RHEB), a critical regulator of mTOR complex 1 activity, is a potential target for T-ALL therapy. In this study, we established an sgRNA library that comprehensively targeted mTOR upstream and downstream pathways, including autophagy. CRISPR/Cas9 dropout screening revealed critical roles of mTOR-related molecules in T-ALL cell survival. Among the regulators, we focused on RHEB because we previously found that it is dispensable for normal hematopoiesis in mice. Transcriptome and metabolic analyses revealed that RHEB deficiency suppressed de novo nucleotide biosynthesis, leading to human T-ALL cell death. Importantly, RHEB deficiency suppressed tumor growth in both mouse and xenograft models. Our data provide a potential strategy for efficient therapy of T-ALL by RHEB-specific inhibition.

Therapeutic advantage of targeting lysosomal membrane integrity supported by lysophagy in malignant glioma

Lysosomes function as the digestive system of a cell and are involved in macromolecular recycling, vesicle trafficking, metabolic reprogramming, and progrowth signaling. Although quality control of lysosome biogenesis is thought to be a potential target for cancer therapy, practical strategies have not been established. Here, we show that lysosomal membrane integrity supported by lysophagy, a selective autophagy for damaged lysosomes, is a promising therapeutic target for glioblastoma (GBM). In this study, we found that ifenprodil, an FDA‐approved drug with neuromodulatory activities, efficiently inhibited spheroid formation of patient‐derived GBM cells in a combination with autophagy inhibition. Ifenprodil increased intracellular Ca²⁺ level, resulting in mitochondrial reactive oxygen species–mediated cytotoxicity. The ifenprodil‐induced Ca²⁺ elevation was due to Ca²⁺ release from lysosomes, but not endoplasmic reticulum, associated with galectin‐3 punctation as an indicator of lysosomal membrane damage. As the Ca²⁺ release was enhanced by ATG5 deficiency, autophagy protected against lysosomal membrane damage. By comparative analysis of 765 FDA‐approved compounds, we identified another clinically available drug for central nervous system (CNS) diseases, amoxapine, in addition to ifenprodil. Both compounds promoted degradation of lysosomal membrane proteins, indicating a critical role of lysophagy in quality control of lysosomal membrane integrity. Importantly, a synergistic inhibitory effect of ifenprodil and chloroquine, a clinically available autophagy inhibitor, on spheroid formation was remarkable in GBM cells, but not in nontransformed neural progenitor cells. Finally, chloroquine dramatically enhanced effects of the compounds inducing lysosomal membrane damage in a patient‐derived xenograft model. These data demonstrate a therapeutic advantage of targeting lysosomal membrane integrity in GBM.

Pillar[6]arene acts as a biosensor for quantitative detection of a vitamin metabolite in crude biological samples

Metabolic syndrome is associated with obesity, hypertension, and dyslipidemia, and increased cardiovascular risk. Therefore, quick and accurate measurements of specific metabolites are critical for diagnosis; however, detection methods are limited. Here we describe the synthesis of pillar[n]arenes to target 1-methylnicotinamide (1-MNA), which is one metabolite of vitamin B3 (nicotinamide) produced by the cancer-associated nicotinamide N-methyltransferase (NNMT). We found that water-soluble pillar[5]arene (P5A) forms host-guest complexes with both 1-MNA and nicotinamide, and water-soluble pillar[6]arene (P6A) selectively binds to 1-MNA at the micromolar level. P6A can be used as a "turn-off sensor" by photoinduced electron transfer (detection limit is 4.38 × 10^-6 M). In our cell-free reaction, P6A is used to quantitatively monitor the activity of NNMT. Moreover, studies using NNMT-deficient mice reveal that P6A exclusively binds to 1-MNA in crude urinary samples. Our findings demonstrate that P6A can be used as a biosensor to quantify 1-MNA in crude biological samples.

Ectopic expression of the CDK inhibitor p21Cip1 enhances deregulated E2F activity and increases cancer cell-specific cytotoxic gene expression mediated by the ARF tumor suppressor promoter

In cancer treatment, specifically targeting cancer cells is important for optimal therapeutic efficacy. One strategy is to utilize a cancer specific promoter to express a cytotoxic gene or a viral gene required for replication. In this approach, the therapeutic window is dependent on the relative promoter activity in cancer cells versus normal cells. Therefore, a promoter with optimal cancer cell-specificity should be used. The tumor suppressor ARF promoter, which specifically responds to deregulated E2F activity, is a potent candidate. Defects in the RB pathway resulting in deregulated E2F activity are observed in almost all cancers. Furthermore, the ARF promoter exhibits greater cancer cell specificity than the E2F1 promoter and consequently, adenovirus expressing HSV-TK under the control of the ARF promoter (Ad-ARF-TK) has more selective cytotoxicity in cancer cells than the analogous E2F1 construct. Ideally, cancer specific gene expression driven by the ARF promoter could be enhanced for optimal therapeutic efficacy, with minimal side effects. We show here that ectopic expression of the CDK inhibitor p21^Cip1 enhanced deregulated E2F activity and pro-apoptotic E2F target gene expression in cancer cells. Moreover, ectopic expression of p21^Cip1 augmented cancer specific cytotoxicity of Ad-ARF-TK, and apoptosis induced by p21^Cip1 was dependent on deregulated E2F activity. These results suggest that p21^Cip1 specifically enhances deregulated E2F activity and that a combination of the CDK inhibitor with Ad-ARF-TK could be effectively employed for cancer therapy.

The phosphatidyl inositol 3 kinase pathway does not suppress activation of the ARF and BIM genes by deregulated E2F1 activity

The transcription factor E2F plays crucial roles in tumor suppression by activating pro-apoptotic genes such as the tumor suppressor ARF. The regulation of the ARF gene is distinct from that of growth-related E2F targets, in that it is specifically activated by deregulated E2F activity, induced by over-expression of E2F or forced inactivation of pRB, but not by physiological E2F activity induced by growth stimulation. The phosphatidyl inositol 3 kinase (PI3K) pathway was reported to suppress expression of some atypical pro-apoptotic genes by over-expressed E2F1. However, the effects of the PI3K pathway on the distinct regulation of typical pro-apoptotic E2F targets have not been elucidated. We examined whether the PI3K pathway suppressed activation of the typical pro-apoptotic E2F targets ARF and BIM. Activation of the PI3K pathway by growth stimulation or introduction of a constitutively active Akt/PKB did not reduce induction of ARF or BIM gene expression or activation of their promoters by over-expressed E2F1. These results suggest that the PI3K pathway does not suppress induction of typical pro-apoptotic genes that are selectively activated by deregulated E2F1.

Abstract LB-148: DDX5 promotes ARF gene expression and apoptosis induced by deregulated E2F1

The transcription factor E2F, the main target of the tumor suppressor pRB, plays central roles not only in cell proliferation but also in tumor suppression. E2F promotes cell proliferation by activating growth-related genes in response to normal growth stimulation. On the other hand, E2F contributes to tumor suppression by activating pro-apoptotic and growth-suppressive genes such as ARF and TAp73 when deregulated from pRB upon dysfunction of pRB, a major oncogenic change. ARF is an upstream activator of the tumor suppressor p53, one of the two major tumor suppressors in addition to pRB. TAp73 is a member of the p53 family and activates p53-responsive genes. Importantly, physiological E2F activity induced by growth stimulation does not activate the latter genes, underscoring importance of deregulated E2F activity in tumor suppression upon oncogenic changes. However, the regulatory mechanism of deregulated E2F activity is not known in detail.

We found that deletion of N-terminal domain of E2F1 dramatically reduced its ability to activate ARF and TAp73 promoter, suggesting that E2F1 interacts with a factor(s) through its N-terminal domain to activate the tumor suppressor genes. Hence we explored novel E2F1-interacting factors using co-immunoprecipitation and LC/MS. Among the candidates, we found DEAD box 5 (DDX5) that functions not only RNA helicase but also transcriptional coactivator. DDX5 is reported to function as a coactivator for p53. Furthermore, E2F1 activity is regulated in similar manners as p53 such as by Chk1 and PRMT5. These observations suggest that DDX5 enhances not only p53 activity but also deregulated E2F1 activity. We thus examined effect of DDX5 on deregulated E2F1 activity induced by overexpression of E2F1.

DDX5 enhanced E2F1 activation of ARF promoter depending on the integrity of N-terminal domain of E2F1. DDX5 mutant lacking RNA helicase activity retained the ability to enhance E2F1 activation of ARF promoter, indicating that the enhancement is independent of helicase activity. Furthermore, DDX5 enhanced endogenous ARF gene expression and apoptosis induced by E2F1 without affecting E2F1 expression level. Finally, knock down of DDX5 reduced E2F1-mediated activation of ARF promoter and ARF gene expression. These results suggest that DDX5 upregulates deregulated E2F1 activity and contributes to E2F1-induced apoptosis to protect cells from tumorigenesis.

Citation Format: Kenta Kurayoshi, Kiyoshi Ohtani. DDX5 promotes ARF gene expression and apoptosis induced by deregulated E2F1. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-148.

Identification of novel target genes specifically activated by deregulated E2F in human normal fibroblasts

The transcription factor E2F is the principal target of the tumor suppressor pRB. E2F plays crucial roles not only in cell proliferation by activating growth-related genes but also in tumor suppression by activating pro-apoptotic and growth-suppressive genes. We previously reported that, in human normal fibroblasts, the tumor suppressor genes ARF, p27(Kip1) and TAp73 are activated by deregulated E2F activity induced by forced inactivation of pRB, but not by physiological E2F activity induced by growth stimulation. In contrast, growth-related E2F targets are activated by both E2F activities, underscoring the roles of deregulated E2F in tumor suppression in the context of dysfunctional pRB. In this study, to further understand the roles of deregulated E2F, we explored new targets that are specifically activated by deregulated E2F using DNA microarray. The analysis identified nine novel targets (BIM, RASSF1, PPP1R13B, JMY, MOAP1, RBM38, ABTB1, RBBP4 and RBBP7), many of which are involved in the p53 and RB tumor suppressor pathways. Among these genes, the BIM gene was shown to be activated via atypical E2F-responsive promoter elements and to contribute to E2F1-mediated apoptosis. Our results underscore crucial roles of deregulated E2F in growth suppression to counteract loss of pRB function.

Cancer cell specific cytotoxic gene expression mediated by ARF tumor suppressor promoter constructs

In current cancer treatment protocols, such as radiation and chemotherapy, side effects on normal cells are major obstacles to radical therapy. To avoid these side effects, a cancer cell-specific approach is needed. One way to specifically target cancer cells is to utilize a cancer specific promoter to express a cytotoxic gene (suicide gene therapy) or a viral gene required for viral replication (oncolytic virotherapy). For this purpose, the selected promoter should have minimal activity in normal cells to avoid side effects, and high activity in a wide variety of cancers to obtain optimal therapeutic efficacy. In contrast to the AFP, CEA and PSA promoters, which have high activity only in a limited spectrum of tumors, the E2F1 promoter exhibits high activity in wide variety of cancers. This is based on the mechanism of carcinogenesis. Defects in the RB pathway and activation of the transcription factor E2F, the main target of the RB pathway, are observed in almost all cancers. Consequently, the E2F1 promoter, which is mainly regulated by E2F, has high activity in wide variety of cancers. However, E2F is also activated by growth stimulation in normal growing cells, suggesting that the E2F1 promoter may also be highly active in normal growing cells. In contrast, we found that the tumor suppressor ARF promoter is activated by deregulated E2F activity, induced by forced inactivation of pRB, but does not respond to physiological E2F activity induced by growth stimulation. We also found that the deregulated E2F activity, which activates the ARF promoter, is detected only in cancer cell lines. These observations suggest that ARF promoter is activated by E2F only in cancer cells and therefore may be more cancer cell-specific than E2F1 promoter to drive gene expression. We show here that the ARF promoter has lower activity in normal growing fibroblasts and shows higher cancer cell-specificity compared to the E2F1 promoter. We also demonstrate that adenovirus expressing HSV-TK under the control of the ARF promoter shows lower cytotoxicity than that of the E2F1 promoter, in normal growing fibroblasts but has equivalent cytotoxicity in cancer cell lines. These results suggest that the ARF promoter, which is specifically activated by deregulated E2F activity, is an excellent candidate to drive therapeutic cytotoxic gene expression, specifically in cancer cells.

Comparative study between daily and 5-days-a-week administration of oral 5-fluorouracil chemotherapy in mice: determining the superior regimen

BACKGROUND

Oral administration of derivatives of 5-fluorouracil (5-FU) is currently used to treat colorectal cancer in the United States. Oral chemotherapy possesses certain advantages: it is simple, easy to administer, and has few side effects. We compared conventional daily oral administration of 5-FU (daily schedule) with administration on 5 consecutive days followed by 2 drug-free days (5-days-a-week schedule) in a mouse tumor model.

METHODS

The maximal tolerated dose (MTD) in the 5-days-a-week schedule and in the daily schedule were determined in 6-week-old non-tumor-bearing CDF1 male mice. In antitumor experiments, CDF1 mice were inoculated subcutaneously with Colon26 cells (1x10(6) per mouse). Antitumor efficacy was evaluated in terms of the ratio of tumor size in treated to control mice (T/C ratio).

RESULTS

The MTD of 5-FU in the 5-days-a-week schedule was 42 mg/kg, and in the daily schedule was 29 mg/kg. In the 5-days-a-week schedule dose escalation nearly 1.4 times that in the daily schedule was possible, although the total dose over 7 days was similar between the two schedules (203 mg/kg and 210 mg/kg, respectively). When the doses of 5-FU were compared under the condition of no body weight loss, the 5-days-a-week schedule produced a comparative dose escalation of 2.1 times per day (from 20 to 42 mg/kg), and 1.5 times per total weekly amount (from 140 to 210 mg/kg) compared to the daily schedule. With regard to the antitumor effect as indicated by the T/C ratio, the 5-days-a-week schedule produced over 70% tumor suppression, whereas the daily schedule produced only 50% suppression at the MTD. Therapeutic efficacy was calculated in terms of the ratio of body weight change to antitumor effect (T/C ratio), and revealed that the MTD of 42 mg/kg 5-FU in the 5-days-a-week schedule produced a therapeutic efficacy almost three times that of the MTD of 29 mg/kg 5-FU in the daily schedule (P<0.001).

CONCLUSIONS

Using oral administration of 5-FU, we confirmed that the 5-days-a-week schedule allowed dose intensity escalation and was superior to the daily schedule in both enhancement of antitumor effect and protection against adverse effects.

p53 as an indicator of lymph node metastases in invasive early colorectal cancer

We examined whether overexpression of p53 can be used as a new genetic marker to predict the presence of lymph node metastases of early invasive colorectal cancer. Forty-nine patients with primary colorectal adenocarcinomas invading to the submucosa (sm-CRC) were analyzed and 7 patients were found to have lymph node metastases. Immunostaining was used to detect the p53 overexpression; 43% of sm-CRC stained positive for p53 and all the cancer cells metastasized to lymph nodes were p53 positive. Both lymph node involvement and tumor budding were significantly more frequent in p53 positive than p53 negative tumors (p < 0.05, respectively), and multivariate analysis showed that p53 overexpression constituted a higher relative lisk for lymph node metastases of sm-CRC than either histologic type, level of sm invasion, macroscopic type, tumor budding or vascular invasion, although the difference was not significant (p = 0.086). We concluded that p53 overexpression is a useful biological marker of lymph node metastases of sm-CRC, and that p53 negative status may be an indicator for limited surgery, such as local excision of sm-CRC.

[Enhanced induction of apoptosis of human colorectal cancer cells after preoperative treatment with 5-fluorouracil its relationship to DNA ploidy pattern]

We examined the relationship between apoptosis induced by 5-fluorouracil (5-FU) that was given preoperatively to colorectal cancer patients and DNA ploidy pattern, and investigated the cell cycle changes, and the expression of Ki-67. Twenty-nine patients with advanced colorectal cancer were divided into four groups, 3 days, 5 days, 7 days, and 10 days. Groups received continuous intravenous 5-FU at 500 mg/body/day preoperatively. Then, patients were divided into two groups by DNA ploidy pattern, diploid(D) and aneuploid(A). Apoptotic cells were stained by the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) method. The expression of Ki-67 was examined by immunohistochemical staining. We used flow cytometry (FCM) for analysis of cell cycle distribution. Apoptosis of cancer cells was mostly increased in 7 days 5-FU administration in both D and A groups. The expression of Ki-67 was reduced according to the prolongation of the term of 5-FU administration in both D and A groups. We assessed S-phase fraction (SPF) to evaluate the cell cycle changes by 5-FU. Tumor samples of all patients after injection of 5-FU showed S-phase accumulation. The ratio of SPF (after 5-FU/before 5-FU) was the highest in the 5-day 5-FU administration group in both D and A groups. We concluded that apoptosis and S-phase accumulation were increased, and proliferative activity was decreased by preoperative 5-FU administration in colorectal cancer patients. However, there was no clear correlation between DNA ploidy pattern and these changes.

[DNA index as a significant prognostic indicator of colorectal cancer]

To investigate the prognostic significance of DNA ploidy pattern and DNA index (DI), DNA contents were measured by flow cytometer in 412 patients with colorectal cancer and correlation between their prognoses and DNA contents were analyzed on the same clinical stage. There were significant differences in the survival rate and the incidence of tumor recurrence between diploid and aneuploid tumors, especially the poor survival rate and frequent tumor recurrence in the aneuploid tumor with DI above 1.5. Cox's multiple regression proportional hazard model was used to investigate the prognostic value of DNA ploidy pattern, DI and clinicopathological findings. From these analyses, DI 1.5 was found to be the most significant prognostic factor. These results suggest that flow cytometrically evaluated DI values have a relevant independent power for predicting the clinical outcome of colorectal cancer patients.

[Flow cytometric measurement of p53 protein and DNA content in colorectal carcinomas with liver metastasis]

To investigate the possible relation between p53 protein, DNA content and liver metastasis of colorectal cancer, overexpression of p53 and DNA content were measured by flowcytometer in 113 primary lesions, which included 34 cases with simultaneous liver metastasis and 79 cases with curative resection, and 25 metastatic lesions of the liver. Overexpression of p53 and DNA aneuploidy were found in 44 (38.9%) and 77 (68.1%) of 113 primary lesions, respectively. However, p53 protein and DNA aneuploidy were unrelated to the clinicopathological findings, such as liver metastasis, venous invasion and lymph node metastasis. Comparing the overexpression of p53 protein between primary and metastatic lesions, p53 protein was recognized in 18 (72.0%) of 25 metastatic lesions of the liver. Incidence of p53 protein was significantly higher in metastatic lesions of the liver than in primary lesions (p < 0.01). On the other hand, p53 protein was found in 27 (60.0%) of 45 diploid lesions and in 35 (37.6%) of 93 aneuploid lesions. There was a significant difference in p53 protein between diploid and aneuploid tumors (p < 0.05). These results suggest that p53 protein may not correlate with the occurrence of liver metastasis and might be produced in the metastatic lesion of the liver after metastasis.

Relationship between the cell-proliferative activity of gastric cancers and that of the normal epithelium

Samples of gastric carcinomas and of normal gastric mucosa adjacent to tumors from 104 patients with primary mucosal gastric cancer were analysed by flow-cytometry. These patients were divided into two groups according to the histologic type of their tumors (differentiated group and undifferentiated group). The pattern of DNA ploidy and the sizes of the S- and G2M-phase fractions (percentages of cells at each respective phase) were compared between these two groups. DNA aneuploidy was encountered in 25.4% of the cases in the differentiated group and in 21.2% of the cases in the undifferentiated group. The mean sizes of S- and G2M-phase fractions of carcinomas in the differentiated group were 8.85% and 3.75% and they were significantly higher than the mean sizes of S- and G2M-phase fractions of carcinomas in the undifferentiated group (6.97% and 2.92%). Moreover, the S-phase fraction of normal gastric mucosa adjacent to the differentiated adenocarcinoma was 5.75% and this value was significantly higher than that of normal gastric mucosa adjacent to undifferentiated adenocarcinoma (4.80%). These results suggest that the proliferative activity of mucosal gastric cancer cells, as described by flow-cytometry, is higher in cases of differentiated adenocarcinoma than in cases of undifferentiated adenocarcinoma, and that the proliferative activity of normal cells in the gastric mucosa close to where adenocarcinoma develops is higher in cases of differentiated adenocarcinoma than in cases of undifferentiated adenocarcinoma. Thus, differentiated adenocarcinoma seems to develop from gastric mucosa with high proliferative activity.

Prophylactic portal infusion chemotherapy as adjuvant therapy for the prevention of metachronous liver metastasis in colorectal cancer

The DNA ploidy and DNA indices (DI) of 414 patients with colorectal cancer were analyzed, and the incidence of patients with metachronous liver metastasis was found to be significantly higher in those with aneuploid tumors and a DI above 1.5 than in those with aneuploid tumors and a DI below 1.4, or in those with diploid tumors and a DI equal to 1.0. Next, to confirm the effectiveness of administering prophylactic portal infusion chemotherapy (PPIC) as adjuvant therapy for the prevention of metachronous liver metastasis in colorectal cancer, a randomized controlled trial of PPIC was performed on 110 consecutive patients with primary colorectal cancer who had undergone curative resection. Although the incidence of patients with metachronous liver metastasis in the two study groups was not significantly different at 3.3% in the PPIC group and 10.3% in the control group, the incidence in the patients with aneuploidy and a DI above 1.5 was significantly lower in the PPIC group than in the control group. These findings suggest that colorectal cancer with aneuploidy and a DI above 1.5 may have a strong tendency to metastasize to the liver, and that prophylactic portal infusion chemotherapy may be effective for preventing metachronous liver metastasis in such patients.

[A case of Gardner's syndrome associated with thyroid carcinoma]

We report a 22-year-old female who was diagnosed as familial adenomatous polyposis (FAP) associated with thyroid carcinoma. Total thyroidectomy and bilateral neck lymph nodes dissection were performed. Gardner's syndrome was pointed out after an investigation of her family. Total colectomy and ileo-rectal anastomosis were carried out. Colon cancer was not found pathologically. We reviewed 10 cases of FAP with thyroid carcinoma in Japan. Ten out of 11 cases including this patient were female. Thus it is important to pay careful attention to the presence of thyroid carcinoma in the case of FAP or Gardner's syndrome.

[Relation between nuclear DNA content and lymph node metastasis in submucosal early gastric cancer]

To investigate a possible relation between the nuclear DNA content and lymph node metastasis of submucosal early gastric cancer, DNA content was analyzed for 46 patients with lymph node metastasis and 67 patients without nodal metastasis. DNA aneuploidy was found in 20 (43.5%) of 46 patients with lymph node metastasis and in 31 (46.3%) of 67 patients without it. There was no statistical difference in the incidence of aneuploidy between the 2 groups. Among the cases with DNA diploidy, the mean value of S phase fraction was 6.82% in patients with lymph node metastasis and 5.65% in those without metastasis. The mean value of S phase fraction was significantly higher in patients with nodal involvement (p < 0.05). Furthermore, among the cases with DNA aneuploidy, the mean value of G2/M phase fraction was 11.03% in patients with lymph node metastasis and 7.54% in patients without metastasis. The mean value of G2/M phase fraction was significantly higher in patients with nodal involvement (p < 0.05). These findings suggest the significant value of the S and G2/M phase fraction for the prediction of lymph node metastasis in patients with submucosal early gastric cancer.