Genetic analysis of p73 localized at chromosome 1p36.3 in primary neuroblastomas.

BACKGROUND: Human p73, a novel homolog of p53, has recently been cloned and mapped at chromosome 1p36.3, the locus for putative tumor suppressor gene(s) of neuroblastoma (NBL) and other cancers. p73, like p53, inhibits growth and induces apoptosis in neuroblastoma and osteosarcoma cell lines. PROCEDURE: To test the hypothesis that p73 is a NBL suppressor gene, we examined expression, allelo-typing, and mutation of the p73 gene in primary human neuroblastomas. Loss of heterozygosity (LOH) for p73 was performed in 272 primary NBLs using a CT repeat polymorphic marker, which we found in intron 9 of the p73 gene. RESULTS: p73 LOH was observed in 28 out of 151 (19%) informative cases. The high frequency of p73 LOH was significantly associated with sporadic neuroblastomas (P< 0.001), MYCN amplification (P< 0.001), and advanced stages (P< 0.05). Mutational analyses by PCR-SSCP (single strand conformation polymorphism) revealed two mis-sense mutations in 140 NBLs, one somatic and one germline. CONCLUSION: Thus, the present results have shown that mutation of p73 is infrequent in NBLs, although the p73 locus is frequently lost in advanced stage tumors. These suggest that p73 may not be a tumor suppressor in the classic Knudson manner.

The p73 gene is not mutated in oligodendrogliomas which frequently have a deleted region at chromosome 1p36.3.

An allelic loss of the chromosome 1p36 region is frequently found in oligodendrogliomas, which suggests the presence of putative tumor suppressor gene(s) in the region. Since the p73 gene, which encodes a protein with significant homology with p53, is mapped to the 1p36.33 region, we examined genetic alterations of the p73 gene in oligodendrogliomas. We screened 10 specimens for mutation throughout the p73 coding regions by polymerase chain reaction (PCR)-single strand conformation polymorphism analysis and by sequencing aberrantly migrated PCR products. We found several polymorphic nucleotide changes, but no somatic mutations that caused an amino acid change. The p73 gene is thus unlikely to be a tumor suppressor gene for oligodendrogliomas.

[Turcot syndrome].

Turcot syndrome is the association of colorectal polyposis with primary neuroepithelial tumors of the central nervous system such as glioblastoma and medulloblastoma. Including putative patients, more than 150 familial or sporadic cases of the syndrome have been reported in literature. Since early reports, there is considerable controversy regarding the modality of genetic transmission and the distinction from other syndromes like familial adenomatous polyposis(FAP). Recent molecular evidence suggests that Turcot syndrome could be divided into the following two entities based on the distinct genetic backgrounds. (1) True Turcot syndrome(autosomal recessive): Intestinal polyps are less in number(< 100), large in size and apt to transform to the malignant tumor. Brain tumor is mainly diagnosed as glioblastoma or astrocytoma and mismatch repair genes might be involved. (2) FAP-associated type(autosomal dominant): Predisposing to medulloblastoma.

[A case of acute theophylline intoxication with repeated status convulsivus].

We report a 6-month-old female infant with status convulsivus which appeared during intravenous drip infusion of aminophylline. She had an extremely high serum theophylline concentration (79 micrograms/ml), which was effectively reduced by plasmapheresis and dialysis. Three days later, she developed status convulsivus again, though her serum theophylline was undetectable at that time. A CT on 14th day of illness revealed mild widening of frontal sulci and Sylvian fissure. The patient apparently recovered her healthy condition, but psychomotor developmental delay, especially in speech and social behavior, was noted at the age of 2 years 6 months (DQ = 55). A delay of myelination was observed on brain MRI at 4 year 1 months, suggesting an irreversible brain injury caused by theophylline intoxication.

Mutational analysis of p51A/TAp63gamma, a p53 homolog, in non-small cell lung cancer and breast cancer.

p51, a novel family member of human p53, is a recently identified candidate tumor suppressor gene mapped at chromosome 3q28. Like p53, p51 was found to activate p21Waf1/Cip1 and to induce apoptosis. Since the DNA loss at 3q is reported in several cancers including non-small cell lung cancer (NSCLC), we screened for mutations in p51A (TAp63gamma), an isoform of p51 with short C-terminal region, in 80 NSCLCs as well as 85 breast cancers by RT-PCR single strand conformation polymorphism (SSCP) analysis and DNA sequencing. In NSCLCs, p51 was expressed in most tumors at variable levels and we found three missense and one silent mutations: Gln31His (transactivation domain) in two tumors, Ala148Pro (DNA-binding domain) and Leu248Leu (DNA-binding domain). In the tumor with Ala148Pro or the silent mutation, only the mutant gene appeared to be expressed. The modified FASAY method to test the ability of yeast expressing p51A cDNA to grow in medium lacking histidine has revealed that Ala148Pro results in a loss of function, while Gln31His does not. In contrast to NSCLC, no mutation was observed in all 85 breast cancers by the similar method. Our results suggest that, because of infrequent mutation, p51 may not be a Knudson type tumor suppressor in most NSCLCs and breast cancers. Nevertheless, in at least a part of NSCLC, p51 may play a certain role in carcinogenesis in a tissue-specific manner.

p73 at chromosome 1p36.3 is lost in advanced stage neuroblastoma but its mutation is infrequent.

p73, a novel p53 family member, is a recently identified candidate neuroblastoma (NBL) suppressor gene mapped at chromosome 1p36.33 and was found to inhibit growth and induce apoptosis in cell lines. To test the hypothesis that p73 is a NBL suppressor gene, we analysed the p73 gene in primary human NBLs. Loss of heterozygosity (LOH) for p73 was observed in 19% (28/151) of informative cases which included 92 mass-screening (MS) tumors. The high frequency of p73 LOH was significantly associated with sporadic NBLs (9% vs 34%, P<0.001), N-myc amplification (10% vs 71%, P<0.001), and advanced stage (14% vs 28%, P<0.05). Both p73alpha and p73beta transcripts were detectable in only 46 of 134 (34%) NBLs at low levels by RT-PCR methods, while they were easily detectable in most breast cancers and colorectal cancers under the same conditions. They found no correlation between p73 LOH and its expression levels (P>0.1). We found two mutations out of 140 NBLs, one somatic and one germline, which result in amino acid substitutions in the C-terminal region of p73 which may affect transactivation functions, though, in the same tumor samples, no mutation of the p53 gene was observed as reported previously. These results suggest that allelic loss of the p73 gene may be a later event in NBL tumorigenesis. However, p73 is infrequently mutated in primary NBLs and may hardly function as a tumor suppressor in a classic Knudson's manner.

Mutational analysis of the p73 gene localized at chromosome 1p36.3 in colorectal carcinomas.

Genetic alteration of p53, which monitors DNA damage and operates cellular checkpoints, is a major factor in the development of human colorectal carcinoma (CRC). Recently, p73, a novel family member of p53, has been identified and found, like p53, to activate p21Waf1/Cip1 and to induce apoptosis. The p73 gene was mapped at chromosome 1p36.3 which is a region frequently deleted in CRCs and other cancers including neuroblastoma. To assess whether or not p73 is a tumor suppressor gene of CRC, we performed mutational analysis of p73 in 82 colorectal tumor tissues paired with constitutional DNA. Using a microsatellite marker for p73, the loss of heterozygosity (LOH) study was performed and allelic loss of p73 was found in 17% of the CRCs. RT-PCR single strand conformation polymorphism analysis showed no mutation except three polymorphisms in the p73 coding region. In addition, p73 was expressed at higher levels in the CRC tissues than in the normal mucosa or neuroblastoma tissues, though the transcripts were detectable only by the RT-PCR method. Our results suggest that, in CRCs, p73 may not play a role as a tumor suppressor, at least not in a classic Knudson manner.

Dramatic effect of ethosuximide on epileptic negative myoclonus: implications for the neurophysiological mechanism.

Epileptic negative myoclonus (ENM) is a recently defined epileptic seizure type seen in various epileptic syndromes. Although the long-term prognosis appears to be favorable, the treatment of localization-related epilepsy (LRE) with ENM in childhood is sometimes difficult due to the apparently pharmaco-resistant nature of ENM. We evaluated the effects of antiepileptic drugs (AEDs) in 10 patients with ENM. Carbamazepine was administered to eight patients, none of whom improved. Responses to clonazepam and valproic acid were unpredictable, whereas ethosuximide (ESM) achieved complete control of ENM in all six cases treated with this drug as adjunctive therapy. The pharmacological responses of ENM to CBZ and ESM were quite similar to those of absence seizures. According to the SPECT and ictal EEG findings in addition to the pharmacological responses from this study, we favor to postulate that ENM is produced by a direct inhibitory action on the motor cortex resulting in the interruption of voluntary muscle contraction as generated by sharp-slow wave complexes, compatible with the mechanism considered to underlie absence seizures. ENM are refractory to treatment and persisting if the wrong AEDs, such as PHT or CBZ, are selected at the diagnosis of LRE. We recommended a trial of ESM when ENM develops during the clinical course of LRE regardless of etiology.

[A case of hepatocellular carcinoma treated by intra-arterial infusion chemotherapy using THP-adriamycin].

A 46-year-old male with unresectable hepatocellular carcinoma (HCC) comprised of severe liver dysfunction was treated by intra-arterial infusion chemotherapy through an implantable reservoir. During 39 months, a total amount of THP-ADR 420 mg, ADR 70 mg and CDDP 350 mg was infused. Through the therapy, the tumor size on the lateral segment was well controlled, and serum AFP and PIVKA-II levels were also lowered. No severe side effect was observed. The patient was treated on an outpatient basis, and a good quality of life during therapy was maintained. This case suggests that THP-ADR may play an important role in a combined intraarterial chemotherapy for advanced HCC.