[Prediction and preventive strategies for recurrence after surgery for hepatocellular carcinoma]

Many advances have been achieved in the clinical and basic studies on metastasis and recurrence of hepatocellular carcinoma (HCC) over the past 20 years. The achievements mainly include the following aspects: (1) a group of molecules related to metastasis and recurrence including osteopontin have been identified, and multi-molecular predictive models for metastasis have been established and optimized; (2) it has been found that the imbalance of immune response in tumor microenvironment is important in promoting metastasis and can be used to predict metastasis and recurrence; (3) it has been found and confirmed that interferon can prevent postoperative recurrence, and patients with a lower miR-26a expression level can achieve greater benefits; (4) the breakthroughs in liquid biopsy and immunotherapy bring a promising future for the prediction, prevention, and treatment of HCC metastasis and recurrence. However, these predictive models still need to be validated by multi-center studies, and the effects of adjuvant transarterial chemoembolization and targeted therapy with sorafenib still need further evaluation.

Value of alpha-fetoprotein and clinical characteristics in patients with liver neoplasm

This article aimed to investigate the value of α-fetoprotein (AFP) for the diagnosis of hepatocellular carcinoma (HCC) and to evaluate the relationship between AFP and various clinical variables of HCC comprehensively. A retrospective study of postoperative patients diagnosed with liver neoplasm from two Chinese centers was enrolled in our study.A total of 3050 patients were included. The best cut-off point of AFP for the diagnosis of HCC was 20ng/ml with ideal sensitivity (69.74%), specificity (91.18%), LR (4.12) and YI (0.61). Non-HBV infection patients showed the highest specificity (94.44%) but lowest sensitivity (60.13%). In HBV infection. Patients, HBsAg, HBeAb, and HBcAb positive patients had the highest sensitivity (79.55%) and specificity (58.49%). AFP levels increased significantly in symptomatic patients (p=0.011). Those patients with tumor sizes ≥10cm had much higher serum AFP level compared with smaller tumors ones (p=0.014). AFP levels increased remarkably in patients with vascular invasion (p=0.015). Stepwise logistic regression showed tumor size (≥10cm) was an independent predictor of elevated AFP (OR=2.743, 95%CI: 1.167-6.447, P=0.021). The best discriminating AFP value for the diagnosis of HCC is 20ng/ml; HBsAg, HBeAb and HBcAb positive patients have the optimal sensitivity and specificity; tumor size ≥ 10cm is an independent predictor of elevated AFP.

Is FCGR2A a susceptibility gene to systemic lupus erythematosus in Chinese?

Recent genome-wide association scans and replication studies reinforce that FCGR2A is a susceptibility gene in systemic lupus erythematosus (SLE) in Caucasians. However, previous case control studies denied such conclusions in Chinese people. Besides genetic heterogeneity among different ethnicities, copy number variation (CNV), non-homogenous phenotypes and insufficient power may be confounders. We performed a case control study with 1066 Chinese (589 SLE patients and 477 healthy controls) and a meta-analysis based on 2328 SLE patients and 2313 healthy controls. FCGR2A CNV and FCGR2A131H/R [rs1801274] were detected by TaqMan assays. No variation of copy numbers of FCGR2A gene was found in Chinese. A further case control study suggested a dose-response character for FCGR2A131H/R and it affected disease activity, severity and prognosis. Finally, meta-analysis indicated FCGR2A that was a susceptibility gene to SLE in Chinese with an odds ratio of 1.094 and population attributable risk proportion of (PARP) 0.031. By an integrative strategy, we validate that FCGR2A bears no population-specific CNV. FCGR2A131H/R contributes to SLE susceptibility in Chinese, and affects disease activity, severity and prognosis. The undetected association in Chinese derives from under-power rather than any methodological obstacle due to CNV or population-specific genetic effect.

Common genetic changes in hereditary and sporadic pituitary adenomas detected by comparative genomic hybridization

Twenty-four pituitary adenomas, both the sporadic type (n = 18) and the type arising in association with either multiple endocrine neoplasia, type 1 (MEN1; n = 2), or Carney complex (CNC, n = 4) were analyzed by comparative genomic hybridization. Twenty-one (88%) tumors displayed chromosomal alterations. The number of chromosomal aberrations in each tumor varied from 2 to greater than 10. Several recurrent chromosomal abnormalities were identified in this study. The most frequently detected losses of chromosomal material involved 1p (14 of 24, 58%), 11p (11 of 24, 46%), 17 (10 of 24, 42%), 16p (9 of 24, 38%), 4 (8 of 24, 33%), 10p (6 of 24, 25%), 12 (6 of 24, 25%), 20 (6 of 24, 25%), 22q (6 of 24, 25%), 13q (5 of 24, 21%), and 9p (4 of 24, 17%). Copy number increases were detected on 4q (7 of 24, 29%), 17 (8 of 24, 33%), 19 (7 of 24, 29%), 1p (6 of 24, 25%), 5 (6 of 24, 25%), 20 (6 of 24, 25%), 6q (5 of 24, 21%), 13q21-qter (5 of 24, 21%), and 16p (5 of 24, 21%). Chromosome 11 loss, which involved 11p in all cases, was the most significant finding and was common to tumors arising sporadically and in association with MEN1 and CNC. In addition, the majority of the tumors (18 of 24, 75% overall and 86% of all tumors with chromosomal abnormalities) showed involvement of chromosome 1. Tumors had either loss (14 of 24, 58%) or gain (6 of 24, 25%) in the 1p32-1pter region. Finally, changes on chromosome 17, either loss or gain, occurred in 71% (17) of all 24 patients. In summary, all the tumors with chromosomal rearrangements (21 of 24, 88%), whether sporadic pituitary adenomas or those associated with MEN1 or CNC, had alteration(s) of 1p32, 11p, or 17.

Metastatic human hepatocellular carcinoma models in nude mice and cell line with metastatic potential

Metastatic human HCC model is needed for the studies on mechanism and interven tion of metastatic recurrence. By using orthotopic implantation of histologically intact tissues of 30 surgical specimens, a patient-like metastatic model of hu man HCC in nude mice (LCI-D20) and a low metastatic model of human HCC in nude mice (LCI-D35) have been established. All mice with transplanted LCI-D20 tumors exhibited extremely high metastatic ability including spontaneous metasta sis to liver, lungs, lymph nodes and peritoneal seeding. Remarkable difference was also found in expression of some of the invasiveness related genes and growth factors between the LCI-D20 and LCI-D35 tumors. PAI-1 increased gradually following tumor progression in LCI-D20 model, and correlated with tumor size and AFP level. Phasic expression of tissue intercellular adhesio nmolecule-1 in this model was also observed. Using corneal micropocket model, it was demonstrated that the vascular response induced by LCI-D20 tumor was stronger than that induced by LCI-D35 tumor. Similar report on metastatic human HCC model in nude mice and human HCC cell line with metastatic potential was rarely found in the literature. This LCI-D20 model has been widely used for the studies on intervention of metastasis, including anti-angiogenesis, antisense approach, metallopro teinase inhibitor, differentiation inducer, etc. It is concluded that the establ ishment of metastatic human HCC model in nude mice and human HCC cell line with metastatic potential will provide important models for the in vivo and in vitro study of HCC invasiveness, angiogenesis as well as intervention of HCC recurrence.

Chromosome 8p deletion is associated with metastasis of human hepatocellular carcinoma when high and low metastatic models are compared

Recently, we found that chromosome 8p deletion might be associated with hepatocellular carcinoma (HCC) metastasis by analyzing the differences in chromosomal alterations between primary tumors and their matched metastatic lesions of HCC with comparative genomic hybridization (CGH) (Qin et al. 1999). To further confirm this interesting finding, the genomic changes of two models bearing human HCC with different metastatic potentials (LCI-D20 and LCI-D35), and the new human HCC cell line with high metastatic potential (MHCC97) were analyzed by CGH. Gains on 1q, 6q, 7p, and 8q, and losses on 13p, 14p, 19p, 21, and 22 were detected in both LCI-D20 and LCI-D35 models. However, high copy number amplification of a minimum region at 1q12-q22 and 12q, and deletions on 1p32-pter, 3p21-pter, 8p, 9p, 10q, 14q, and 15p were detected only in the LCI-D20 model. Gains on 1p21-p32, 2p13-p21, 6p12-pter, 9p, 15q, and 16q11-q21, and losses on 2p23-pter, 4q24-qter, 7q31-qter, 12q, 17p, and 18 were detected only in the LCI-D35 model. The chromosomal aberration patterns in the MHCC97 cell line were similar to its parent LCI-D20 model, except that gains on 19q and losses on 4, 5, 10q, and 13q were found only in the cell line. These results provide some indirect clues to the metastasis-related chromosomal aberrations of HCC and further support the finding that 8p deletion is associated with HCC metastasis. 1q12-22 and 12q might harbor a novel oncogene(s) that contributes to the development and progression of HCC. Amplification on 8q and deletions on 4q and 17p may be not necessary for HCC metastasis.

Experience of 1000 patients who underwent hepatectomy for small hepatocellular carcinoma

BACKGROUND

Recently, the implementation of screening programs using alpha-fetoprotein (AFP) and ultrasonography in high risk populations has identified increasing numbers of patients with small hepatocellular carcinoma (small HCC). The aim of this study was to summarize the authors' experience in patients who underwent hepatectomy for small HCC and the factors that influence or improve long term survival.

METHODS

The study included 1000 patients who underwent hepatectomy for small HCC (< or = 5 cm) and compared them with 1366 patients who underwent hepatectomy for large HCC (> 5 cm) during the same period. A Cox proportional-hazards model was used for multivariate analysis of prognostic factors.

RESULTS

Comparison between patients with small HCC (n = 1000 patients) and patients with large HCC (n = 1366 patients) revealed that those with small HCC had a higher resection rate (93.6% [1000 of 1068 patients] vs. 55.7% [1366 of 2451 patients]; P < 0.01), a higher curative resection rate (80.5% [805 of 1000 patients] vs. 60.7% [829 of 1366 patients]; P < 0.01), a lower operative mortality rate (1.5% [15 of 1000 patients] vs. 3.7% [50 of 1366 patients]; P < 0.01), better differentiation of tumor cells (Edmondson Grade 3-4; 14.9% vs. 20.1%; P < 0.01), a higher incidence of single nodule tumors (82.6% vs. 64.4%; P < 0.01), a higher proportion of well encapsulated tumors (73.3% vs. 46.3%; P < 0.01), a lower incidence of tumor emboli in the portal vein (4.9% vs. 20.8%; P < 0.01), and higher survival rates after undergoing resection (5 years: 62.7% vs. 37.1%; P < 0.01; 10 years: 46.3% vs. 29.2%; P < 0.01). No significant difference was found between survival after undergoing minor resection (n = 949 patients) or lobectomy (n = 51 patients) in patients with small HCC (P > 0.05). Reresection for subclinical recurrence or solitary pulmonary metastasis after small HCC resection was undertaken in 84 patients.

CONCLUSIONS

Resection is still the modality of first choice for the treatment of patients with small HCC. Minor resection instead of lobectomy was the key to increasing resectability and decreasing operative mortality, and reresection for subclinical recurrence or solitary pulmonary metastasis was important approach to prolonging survival further.

Experience of 1000 patients who underwent hepatectomy for small hepatocellular carcinoma

BACKGROUND

Recently, the implementation of screening programs using alpha-fetoprotein (AFP) and ultrasonography in high risk populations has identified increasing numbers of patients with small hepatocellular carcinoma (small HCC). The aim of this study was to summarize the authors' experience in patients who underwent hepatectomy for small HCC and the factors that influence or improve long term survival.

METHODS

The study included 1000 patients who underwent hepatectomy for small HCC (< or = 5 cm) and compared them with 1366 patients who underwent hepatectomy for large HCC (> 5 cm) during the same period. A Cox proportional-hazards model was used for multivariate analysis of prognostic factors.

RESULTS

Comparison between patients with small HCC (n = 1000 patients) and patients with large HCC (n = 1366 patients) revealed that those with small HCC had a higher resection rate (93.6% [1000 of 1068 patients] vs. 55.7% [1366 of 2451 patients]; P < 0.01), a higher curative resection rate (80.5% [805 of 1000 patients] vs. 60.7% [829 of 1366 patients]; P < 0.01), a lower operative mortality rate (1.5% [15 of 1000 patients] vs. 3.7% [50 of 1366 patients]; P < 0.01), better differentiation of tumor cells (Edmondson Grade 3-4; 14.9% vs. 20.1%; P < 0.01), a higher incidence of single nodule tumors (82.6% vs. 64.4%; P < 0.01), a higher proportion of well encapsulated tumors (73.3% vs. 46.3%; P < 0.01), a lower incidence of tumor emboli in the portal vein (4.9% vs. 20.8%; P < 0.01), and higher survival rates after undergoing resection (5 years: 62.7% vs. 37.1%; P < 0.01; 10 years: 46.3% vs. 29.2%; P < 0.01). No significant difference was found between survival after undergoing minor resection (n = 949 patients) or lobectomy (n = 51 patients) in patients with small HCC (P > 0.05). Reresection for subclinical recurrence or solitary pulmonary metastasis after small HCC resection was undertaken in 84 patients.

CONCLUSIONS

Resection is still the modality of first choice for the treatment of patients with small HCC. Minor resection instead of lobectomy was the key to increasing resectability and decreasing operative mortality, and reresection for subclinical recurrence or solitary pulmonary metastasis was important approach to prolonging survival further.

Experience of 1000 patients who underwent hepatectomy for small hepatocellular carcinoma

BACKGROUND

Recently, the implementation of screening programs using alpha-fetoprotein (AFP) and ultrasonography in high risk populations has identified increasing numbers of patients with small hepatocellular carcinoma (small HCC). The aim of this study was to summarize the authors' experience in patients who underwent hepatectomy for small HCC and the factors that influence or improve long term survival.

METHODS

The study included 1000 patients who underwent hepatectomy for small HCC (< or = 5 cm) and compared them with 1366 patients who underwent hepatectomy for large HCC (> 5 cm) during the same period. A Cox proportional-hazards model was used for multivariate analysis of prognostic factors.

RESULTS

Comparison between patients with small HCC (n = 1000 patients) and patients with large HCC (n = 1366 patients) revealed that those with small HCC had a higher resection rate (93.6% [1000 of 1068 patients] vs. 55.7% [1366 of 2451 patients]; P < 0.01), a higher curative resection rate (80.5% [805 of 1000 patients] vs. 60.7% [829 of 1366 patients]; P < 0.01), a lower operative mortality rate (1.5% [15 of 1000 patients] vs. 3.7% [50 of 1366 patients]; P < 0.01), better differentiation of tumor cells (Edmondson Grade 3-4; 14.9% vs. 20.1%; P < 0.01), a higher incidence of single nodule tumors (82.6% vs. 64.4%; P < 0.01), a higher proportion of well encapsulated tumors (73.3% vs. 46.3%; P < 0.01), a lower incidence of tumor emboli in the portal vein (4.9% vs. 20.8%; P < 0.01), and higher survival rates after undergoing resection (5 years: 62.7% vs. 37.1%; P < 0.01; 10 years: 46.3% vs. 29.2%; P < 0.01). No significant difference was found between survival after undergoing minor resection (n = 949 patients) or lobectomy (n = 51 patients) in patients with small HCC (P > 0.05). Reresection for subclinical recurrence or solitary pulmonary metastasis after small HCC resection was undertaken in 84 patients.

CONCLUSIONS

Resection is still the modality of first choice for the treatment of patients with small HCC. Minor resection instead of lobectomy was the key to increasing resectability and decreasing operative mortality, and reresection for subclinical recurrence or solitary pulmonary metastasis was important approach to prolonging survival further.

Phase I clinical trial of oral furtulon and combined hepatic arterial chemoembolization and radiotherapy in unresectable primary liver cancers, including clinicopathologic study

Surgical resection has been accepted as the only curative therapy for primary liver cancer (PLC). Unfortunately, most patients are surgically unresectable when they seek treatment. An alternative therapeutic approach for some of these patients is transcatheter arterial chemoembolization. However, this is not curative by itself, and additional therapy is required to eradicate residual disease. This study investigates the approach of preoperative hepatic arterial chemoembolization followed by the combination of oral Furtulon (5'-deoxy-5-fluorouridine) as a radiosensitizer and external beam radiotherapy (RT). From July 1997 to December 1998, 25 patients with unresectable PLC were treated with hepatic arterial chemoembolization followed by limited-field radiotherapy plus oral Furtulon as a radiosensitizer. Hepatic arterial chemoembolization was performed with 5-fluorouracil 1 g, cisplatin 80 mg (DDP), mitomycin C (MMC) 10 mg, and arterial embolization with iodized oil-10 ml mixed with 10 mg MMC. Hepatic arterial chemoembolization was performed at regular intervals of 6 weeks, and the patients then received limited-field RT. Mean tumor dose was 4,600 cGy (range, 4,100-5,200 cGy) in daily 1.8-Gy fractions, 5 times a week. The toxicity and responses between RT and surgery were assessed. After surgical evaluation, resection was performed. The histopathologic study was also performed in the specimens of both normal and radiation-injured liver tissues from the patients who underwent resection. Seventeen of 25 patients (68%) showed an objective response. One patient with cholangiocarcinoma involving the portal lymph nodes attained a complete response. Eight patients (32%) underwent sequential resection. The most common toxicity was an increase in liver enzymes, which were less than twofold of the upper limit of normal. Follow-up computed tomography studies after treatment showed a low-attenuation area adjacent to the hepatic tumor in the target volume. On pathologic evaluation, the low-attenuation area revealed hyperemia, distended hepatic sinusoids packed with erythrocytes, and hepatic cell loss when examined with microscopy; "new-born" hepatocytes, hepatic cords in the process of forming, and endothelial cells have appeared on electronic microscopic examination. The combination of hepatic arterial chemoembolization and external radiotherapy is efficacious and a safe modality for unresectable primary liver cancers. Furtulon offers the potential for use as a clinical radiosensitizer. Radiation can significantly damage the liver tissue between 41 Gy and 52 Gy, but the new hepatocytes were forming within the radiation-injured liver after RT.

High-dose and long-term therapy with interferon-alfa inhibits tumor growth and recurrence in nude mice bearing human hepatocellular carcinoma xenografts with high metastatic potential

Postoperative recurrence of human hepatocellular carcinoma (HCC) is the major issue that must be addressed to further improve prognosis. This study was undertaken to investigate the effects of interferon-alfa-1b (IFN-alpha-1b) on recurrent tumor and metastasis after curative resection in nude mice bearing an HCC xenograft with high metastatic potential. Tumor tissues from LCI-D20, a metastatic model of HCC in nude mice, were orthotopically implanted in 105 nude mice. Eleven days later, 64 mice underwent curative resection of liver tumors. IFN-alpha at different doses was administered subcutaneously to mice with or without resection. In mice without resection, when comparison was made among control, IFN 7.5 x 10(6) U/kg/day, 1.5 x 10(7) U/kg/day for treated groups, and 3 x 10(7) U/kg/day; tumor volume was 8,475 mm(3) +/- 2,636 mm(3), 7,963 mm(3) +/- 3,214 mm(3), 769 mm(3) +/- 287 mm(3), and 13 mm(3) +/- 9 mm(3); incidence of lung metastasis being 100%, 80%, 40%, and 0%; life span was 45 +/- 4 days, 53 +/- 8 days, 81 +/- 6 days, and 105 +/- 24 days, respectively. In mice with curative resection, when comparison was made among control, IFN 5 x 10(5) U/kg/day, 1 x 10(6) U/kg/day, 4 x 10(6) U/kg/day, 7.5 x 10(6) U/kg/day, 1.5 x 10(7) U/kg/day, and 3 x 10(7) U/kg/day for treated groups; incidence of recurrent tumor was 100%, 100%, 87.5%, 100%, 87.5%, 62.5%, and 12.5%; lung metastasis being 100%, 75%, 87.5%, 50%, 62.5%, 0%, and 0%, respectively. IFN-alpha inhibited neovascularization induced by LCI-D20 tumor specimens implanted into the micropocket of nude mice corneas. In conclusion, high-dose and long-term therapy with IFN-alpha dose-dependently inhibits tumor growth and recurrence after resection of HCC. The effect of IFN-alpha may be attributed to antiangiogenesis in this experiment. These results provide potential clinical implication, particularly for the prevention of recurrence after curative resection of HCC.

Effect of TT virus infection on hepatocellular carcinoma development: results of a Euro-Asian survey

A small percentage of persons with hepatocellular carcinoma (HCC) lack identifiable causes of liver pathology. The single-stranded DNA virus, TT virus (TTV), has been found in persons with acute and chronic liver injury. Nested polymerase chain reaction was used to search for both TTV and parvoviruses in 293 HCC samples from Asia and Europe. TTV was found in >30% of Chinese and Italian samples but in only 13% of French samples. No clinicopathologic differences were found between TTV-positive and -negative populations. A significant association was found between TTV infection and hepatitis B virus (P<.01) and herpesviruses (P<.02) in HCC patients, suggesting that factors promoting these infections are associated with enhanced TTV positivity. Parvovirus B19 and adeno-associated virus were found in only 7.5% of the tumors. Taken together, these data suggest that TTV infection is unlikely to be associated with the induction or acceleration of the hepatocarcinogenic process in humans.

Serum vascular endothelial growth factor is a predictor of invasion and metastasis in hepatocellular carcinoma

Tumor progression is angiogenesis dependent, and vascular endothelial growth factor (VEGF) is a key growth factor in this process. sVEGF concentrations in 44 patients with hepatocellular carcinoma (HCC) and 5 with benign liver lesions were determined with an enzyme-link immunoadsorbent assay system (ELISA). Reverse transcript-polymerase chain reaction (RT-PCR) was carried out on surgical specimens of 51 patients with HCC. The relative levels of VEGF mRNA expression were measured by determining a ratio between PCR products of VEGF and the endogenous internal standard gene b-actin. UEA-1 was histochemically used to count microvascularity in tumor tissue. Elevated sVEGF concentrations were found in patients with HCC (172.84+/-111.75 pg/ml) as compared to individuals with benign liver lesions (95.74+/-36.20 pg/ml, P<.05). Of 44 cases with HCC, sVEGF concentrations in the patients with PV-emboli or with poor-encapsulated tumors were significantly higher than in those without PV-emboli or with well-encapsulated tumors (P<0.05). The expression levels of VEGF mRNA in tumors with PV-emboli and in poor-encapsulated tumors were higher than in those without PV-emboli and in well-encapsulated tumors (P<0.05). Microvascular density in HCC tissues was significantly correlated with the expression levels of VEGF mRNA (P<0.01; r=0.7). Circulating VEGF was derived from HCC tissue. sVEGF concentrations could be a new marker for predicting the angiogenesis, invasion and metastasis of HCC.

The association of chromosome 8p deletion and tumor metastasis in human hepatocellular carcinoma

To understand the genetic mechanisms underlying the progression of hepatocellular carcinoma (HCC) metastasis, differences of genomic alterations between 10 pairs of primary HCC tumors and their matched metastatic lesions were analyzed by comparative genomic hybridization. Several chromosomal alterations including loss of 8p, 4q, 17p, and 19p, gain of 5p and high-level amplification of 1q12-q22 were detected in two or more cases. The most significant finding is the loss of 8p which was detected in 8 metastatic tumors but only in 3 corresponding primary tumors (P = 0.03). This result suggests that the deletion of chromosome 8p might contribute to the development of HCC metastasis. Another interesting result is the detection of a minimum high-level amplification region at 1q12-q22 in HCC. This result provides a candidate amplification region in HCC for further study to identify amplified oncogenes related to the development or progression of HCC. Finally, this study provides a practicable model to detect specific genetic alterations related to the tumor metastasis through comparing the primary tumor and its corresponding metastatic lesion using comparative genomic hybridization technique.

Effect of antiangiogenic agents on experimental animal models of hepatocellular carcinoma

A new therapeutic strategy for treating metastasis in hepatocellular carcinoma (HCC) has entailed the use of antiangiogenic agents such as suramin, BB-94 (Batimastat), TNP-470, and carboxyamido-triazole (CAI, a synthetic inhibitor of non-excitable calcium channels that reversibly inhibits angiogenesis). These agents have been used to treat metastatic model of HCC in nude mouse (LCI-D20 mouse model). The results of these studies are summarized in this paper with emphasis on the inhibitory effects of the drugs on tumour growth, angiogenesis, invasion and metastasis in LCI-D20 mouse models. The results suggest that all of the agents used can significantly inhibit tumour growth, angiogenesis, invasion and metastasis of human HCC in nude mouse models, and may be candidates for the control of recurrence and metastasis after HCC resection.

G2-and early-M-specific expression of the NTCYC1 cyclin gene in Nicotiana tabacum cells

We have previously reported the isolation of a cDNA encoding a mitotic cyclin, NTCYC1, from a tobacco cell suspension library. Here we describe the expression patterns of NTCYC1 and of Ntsuc1, a suc 1 plant homologue, in synchronized tobacco cell suspensions. Furthermore, the expression pattern of this cyclin is compared to that of Ntcdc2-1, a Nicotiana tabacum homologue of cdc2. While no NTCYC1 transcript was detected in cells synchronized in the G1 and S phases, NTCYC1 expression was observed in late G2 and early M phases, disappearing in the G1' of a new cell cycle. On the other hand, Ntsuc1 and Ntcdc2-1 exhibited a constitutive expression during the cell cycle. A functional analysis performed by microinjecting NTCYC1 mRNA into immature Xenopus oocytes, indicates that NTCYC1 could participate in the control of the G2/M transition in plant cells. Subsequently NTCYC1 expression was used to assess the status of mesophyll cells in expanded leaves of N. tabacum. Depending on leaf position along the shoot axis, a large population of mesophyll cells appeared with a 4C DNA content, suggesting a G2 arrest. It was found that leaves with such a population also contained high levels of NTCYC1 transcripts. With respect to these results concerning a naturally occurring G2-arrested cell population, the regulation of NTCYC1 expression in planta is discussed.

Clustered genes within the genome of Arabidopsis thaliana encoding pectin methylesterase-like enzymes

We focused our attention on the isolation and regulation of genes encoding for pectin methylesterase (PME) isoenzymes in Arabidopsis thaliana (At). The present data reports the identification of two PME-like genes, named AtPME1 and AtPME2, that are closely linked in the At genome. These genes possess different structural organisations. While all higher plant PME characterised so far possess an intron at a similar location relative to their coding sequence, AtPME2 shows an additional intron whose presence within other higher plant PME-like genes has not been previously reported. Sequence comparison of the N-terminal region suggests that the secretory pathways of the putative AtPME1 and AtPME2 isoforms are different, and that this region may contribute to specify a biological function to each isoform. Moreover, phylogenetic analysis reflects the possible existence of functional groups of PME isoforms in higher plant species that seem to have been conserved during evolution.

Molecular cloning and characterisation of a putative pectin methylesterase cDNA in Arabidopsis thaliana (L.)

Pectin methylesterase (PME) is a cell wall enzyme that catalyses the de-esterification of pectins leading to fundamental changes which confer new properties to the micro-environment of each cell. In order to elucidate the meaning of PME-mediated changes of pectin in the time course of cell differentiation, we attempted to study the regulation of PME genes in Arabidopsis thaliana. In this report, the first full cDNA sequence showing sequence similarities with other PME genes characterised so far in other plant species has been isolated from an Arabidopsis shoot cDNA library. This ATPMEl cDNA is 1,970 bp long and contains an open reading frame encoding a protein of 64.1 kDa and a basic pI of 8.7 as predicted from the nucleotide sequence. Northern blot analyses denoted changes in the expression level of the ATPMEl mRNA according to plant organs. High mRNA levels were found in young developing organs such as cauline leaves while they were significantly lower in rosette leaves, stems and inflorescences, and almost undetectable in roots. Beside this molecular approach, isoelectrofocusing analyses revealed the occurrence of three PME isoforms in Arabidopsis. Two PME isoforms with pI values of 4.9 and 9.1 were found throughout the plant, but at a higher level in the root, while an other PME isoform with a pI of 5.7 was essentially detected in the inflorescence. The relationship between our observations and the data reported for other plant species is discussed.

Olomoucine, an inhibitor of the cdc2/cdk2 kinases activity, blocks plant cells at the G1 to S and G2 to M cell cycle transitions

The cdc2/cdk2 protein kinases play key roles in the cell cycle at two control points: the G1/S transition and the entry into mitosis. Olomoucine, a specific inhibitor of these kinases, was tested in two plant cell systems: Petunia mesophyll protoplasts induced to divide and Arabidopsis thaliana cell suspension cultures. The cell cycle status was analysed from DNA histograms or through continuous labelling of cells with 5-bromodeoxyuridine (BrdUrd) followed by double staining with bis-benzimide (Hoechst 33258) and propidium iodide (PI). Such analyses resolve cells from several generations according to the extent of their DNA replication. Olomoucine was shown to reversibly arrest differentiated Petunia cells induced to divide at G1 phase and cycling Arabidopsis cells in late G1 and G2. A comparison of the effects of aphidicolin, oryzalin and olomoucine suggests that in the Arabidopsis cell suspension culture, a cdc2/cdk2-like kinase is activated at a restriction point in late G1.

Petunia p34cdc2 protein kinase activity in G2/M cells obtained with a reversible cell cycle inhibitor, mimosine

Protoplasts isolated from petunia leaf mesophyll are non-cycling cells mostly with 2C content. Cells regenerating from protoplast culture enter mitosis after 48 h. This experimental model is used to relate p34cdc2 kinase activity to cell cycle phase. Our results show that the histone H1 phosphorylation, and hence p34cdc2 kinase activity, peaks with G2+early M cell cycle phase. However, a trace kinase activity was already present when most cells were entering S phase. To obtain a maximum of cells in G1+S phases, the protoplast culture was treated with the rare amino acid, mimosine. Mimosine blocked plant cells derived from protoplast culture both at G1 and in early and mid S phase. Despite the increased G1+S level, p34cdc2 kinase activity did not increase. This suggests that the trace activity appearing when the majority of cells are entering S does not correspond to any putative p34cdc2 activation at G1/S transition but to the activation of the minor 4C population initially present in the leaf: the hypothesis remains that p34cdc2 kinase activity is solely related to G2+M phase in petunia.

Studies on monoclonal anti-idiotypic and anti-isotypic antibodies against leukemia and myeloma: III. Analysis of monoclonal antibodies recognizing the antigenic epitopes by use of ELISA additivity test and microcomputer grouping programme

ELISA double antibodies additivity test was employed to identify the epitopes which can be recognized by monoclonal antibodies (McAbs) against IgM of a patient with B chronic lymphocytic leukemia (B-CLL). The computer grouping programme analysis showed that 4 anti-isotype McAbs could be divided into two groups and 10 anti-idiotype McAbs could be divided into four groups. The result was consistent with that of the indirect ELISA, ELISA sandwich as well as ELISA inhibition test. The above findings suggested that there are at least 6 distinct IgM epitopes which can specifically react with 14 McAbs. Our study indicated that the combination of the ELISA additivity test and the computer grouping programme analysis provides a helpful tool for researchers into the relationship between the structure and function of antigens.