The M1 subunit of ribonucleotide reductase refines mapping of genetic rearrangements at chromosome 11p15

Ribonucleotide reductase is an effective target to overcome gemcitabine resistance in gemcitabine-resistant pancreatic cancer cells with dual resistant factors

Gemcitabine is widely used for pancreatic, lung, and bladder cancer. However, drug resistance against gemcitabine is a large obstacle to effective chemotherapy. Nucleoside transporters, nucleoside and nucleotide metabolic enzymes, and efflux transporters have been reported to be involved in gemcitabine resistance. Although most of the resistant factors are supposed to be related to each other, it is unclear how one factor can affect the other one. In this study, we established gemcitabine-resistant pancreatic cancer cell lines. Gemcitabine resistance in these cells is caused by two major processes: a decrease in gemcitabine uptake and overexpression of ribonucleotide reductase large subunit (RRM1). Knockdown of RRM1, but not the overexpression of concentrative nucleoside transporter 1 (CNT1), could completely overcome the gemcitabine resistance. RRM1 knockdown in gemcitabine-resistant cells could increase the intracellular accumulation of gemcitabine by increasing the nucleoside transporter expression. Furthermore, a synergistic effect was observed between hydroxyurea, a ribonucleotide reductase (RR) inhibitor, and gemcitabine on the gemcitabine-resistant cells. Here we indicate that RR is one of the most promising targets to overcome gemcitabine resistance in gemcitabine-resistant cells with dual resistant factors.

Expression of a high molecular weight form of insulin-like growth factor II in a Beckwith-Wiedemann syndrome associated adrenocortical adenoma

Beckwith-Wiedemann syndrome is a rare condition (1/13,700 live births) occurring in both inherited and sporadic forms in the population. It is manifest as a fetal overgrowth syndrome, in which hypertrophy dominates the clinical picture. An additional complication is that these children are predisposed to a specific subset of childhood neoplasms, amongst which are Wilms' tumour and adrenocortical carcinoma. We report here the synthesis by an associated adrenal tumour of large quantities of a high molecular weight form of insulin-like growth factor II (IGF-II), associated with profound suppression of circulating IGFs in the patient's serum. As with other tumours of this type, the tumours showed loss of material on chromosome 11p.

Homozygous intragenic deletion in the WT1 gene in a sporadic Wilms' tumour associated with high levels of expression of a truncated transcript

We have examined a panel of 21 sporadic Wilms' tumours for rearrangements in the Wilms' tumour suppressor gene, WT1. In one tumour with specific allele loss in chromosome 11p13, a homozygous deletion in the 3' end of the gene, encompassing exon 10 and the 3' untranslated region, was identified. High levels of a truncated WT1 transcript, predicted to encode a polypeptide missing the fourth zinc finger were expressed in this tumour. All other samples showed normal patterns of digestion on Southern blots. This observation confirms previous findings that large deletions in the gene occur infrequently in sporadic Wilms' tumours and that the zinc-finger region of the encoded polypeptide is critical for correct functioning of the gene.

Correlation of loss of heterozygosity at 11p with tumour progression and survival in non-small cell lung cancer

Loss of heterozygosity (LOH) affecting loci at 11p13 and 11p15 occurs in childhood and adult carcinomas, including non-small cell lung cancer (NSCLC). In NSCLC, the highest reported frequency of LOH was 72% at the 11p13 catalase (CAT) locus. As this locus is centromeric to the Wilms' tumour (WT1) locus, possible involvement of WT1 in the pathogenesis of NSCLC was considered. We thus examined 101 cases of NSCLC for LOH at the WT1 and five other polymorphic loci along 11p. At 11p13, the frequencies of LOH were 20% (9/46) at the FSHB locus, 9% (5/53) at the WT1 locus, and 15% (6/41) at the CAT locus. The shortest region of overlap (SRO) at 11p13 was mapped centromeric to, but excluding, the WT1 locus. Only adenocarcinomas showed LOH in this region. At 11p15, LOH affected 23% (18/77) of informative cases, with the highest frequency of 36% at the insulin (INS) locus. The SRO at 11p15 was mapped telomeric to the RRM1 locus. A third region, at 11p13-15 between WT1 and RRM1, was also affected by LOH. LOH at 11p correlated significantly with advanced T stage and nodal involvement in NSCLC tumours. In the squamous cell carcinoma subtype, LOH along 11p also correlated with nodal involvement. Furthermore, squamous tumours with LOH involving 11p13 loci had significantly worse survival than those without LOH. These data suggest that tumor suppressor gene(s) on 11p affect the progression of NSCLC, particularly squamous cell carcinomas.

Three non-overlapping regions of chromosome arm 11p allele loss identified in infantile tumors of adrenal and liver

Tumor and constitutional chromosome arm 11p genotypes were compared in 6 hepatoblastoma (HB) patients and 2 adrenal adenoma (AA) patients, with one HB patient and both AA patients displaying clinical features associated with the Beckwith-Wiedemann syndrome (BWS). Using up to 14 chromosome 11 polymorphic markers, loss of constitutional heterozygosity (LOH) was demonstrated in both AA patients and in 4 of 6 HB patients. This identified three distinct and non-overlapping regions of 11p within which LOH occurred, which were defined as lying distal to the gamma-globin locus (11p15.5), proximal to the gamma-globin locus but distal to 11p13 (LOH being detected at 11p15.1), and restricted to the 11p13 region. Specific LOH within each 11p15 region was observed in HB, and this represents the first demonstration by a single study of LOH clearly affecting separate regions of chromosome band 11p15 in a particular tumor type. One AA showed LOH restricted to 11p13 loci, implicating the involvement of the WT1 gene. The second AA patient presented with genitourinary abnormalities and we therefore examined sequences coding for 3 zinc finger domains of WT1 in both AAs. No point mutations were identified in sequence from either patient. Nonetheless our results indicate that 3 separate 11p loci may be significant in the development of tumors which arise in association with BWS.

Beckwith-Wiedemann syndrome, tumourigenesis and imprinting

The concurrent development of cytogenetic, clinical, genetic and molecular studies has led to the recognition that the different hereditary and non-hereditary forms of the Beckwith-Wiedemann syndrome and associated tumours result from an imbalance between maternal and paternal alleles. The most exciting development in the past year was the discovery of uniparental paternal disomy and the increased understanding, arising from studies in the mouse and in hereditary cases, of the role possibly played by imprinting and somatic mosaicism in partial and complete expression of this complex syndrome.