Gene replacement with the human BRCA1 locus: tissue specific expression and rescue of embryonic lethality in mice

We have generated transgenic mice that harbor a 140 kb genomic fragment of the human BRCA1 locus (TgN x BRCA1GEN). We find that the transgene directs appropriate expression of human BRCA1 transcripts in multiple mouse tissues, and that human BRCA1 protein is expressed and stabilized following exposure to DNA damage. Such mice are completely normal, with no overt signs of BRCA1 toxicity commonly observed when BRCA1 is expressed from heterologous promoters. Most importantly, however, the transgene rescues the otherwise lethal phenotype associated with the targeted hypomorphic allele (Brca1DeltaexllSA). Brca1-/-; TgN x BRCA1GEN bigenic animals develop normally and can be maintained as a distinct line. These results show that a 140 kb fragment of chromosome 17 contains all elements necessary for the correct expression, localization, and function of the BRCA1 protein. Further, the model provides evidence that function and regulation of the human BRCA1 gene can be studied and manipulated in a genetically tractable mammalian system. Oncogene (2000) 19, 4085 - 4090

Characterization of acute promyelocytic leukemia cases lacking the classic t(15;17): results of the European Working Party. Groupe Français de Cytogénétique Hématologique, Groupe de Français d'Hematologie Cellulaire, UK Cancer Cytogenetics Group and BIOMED 1 European Community-Concerted Action "Molecular Cytogenetic Diagnosis in Haematological Malignancies"

Acute promyelocytic leukemia (APL) is typified by the t(15;17), generating the PML-RAR alpha fusion and predicting a beneficial response to retinoids. However, a sizeable minority of APL cases lack the classic t(15;17), prompting the establishment of the European Working Party to further characterize this group. Such cases were referred to a workshop held in Monza, Italy and subjected to morphologic, cytogenetic, and molecular review, yielding 60 evaluable patients. In the majority (42 of 60), molecular analyses revealed underlying PML/RAR alpha rearrangements due to insertions (28 of 42) or more complex mechanisms, including 3-way and simple variant translocations (14 of 42). Metaphase fluorescence in situ hybridization (FISH) demonstrated that insertions most commonly led to formation of the PML-RAR alpha fusion gene on 15q. In 11 of 60 workshop patients, PLZF/RAR alpha rearrangements were identified, including 2 patients lacking the t(11;17)(q23;q21). In one case with a normal karyotype, FISH analysis revealed insertion of RAR alpha into 11q23, and PLZF-RAR alpha was the sole fusion gene formed. Two patients were found to have t(5;17), one with a diffuse nuclear NPM staining pattern and with NPM-RAR alpha and RAR alpha-NPM transcripts detected. In the other with an unbalanced der(5)t(5;17)(q13;q21) and a nucleolar NPM localization pattern, an NPM/RAR alpha rearrangement was excluded, and FISH revealed deletion of one RAR alpha allele. In the remaining 5 workshop patients, no evidence was found for a rearrangement of RAR alpha, indicating that in rare instances, alternative mechanisms could mediate the differentiation block that typifies this disease. This study highlights the importance of combining morphologic, cytogenetic, and molecular analyses for optimal management of APL patients and better understanding of the pathogenesis of the disease. (Blood. 2000;96:1297-1308)

Bacteremic and nonbacteremic pneumococcal pneumonia. A prospective study

We prospectively identified cases of pneumococcal pneumonia and used stringent criteria to stratify them into bacteremic and nonbacteremic cases. Although patients were distributed among racial groups in proportion to all patients seen at this medical center, the proportion of African-Americans with bacteremic disease was significantly increased. All patients had at least 1 underlying condition predisposing to pneumococcal infection, and most had several. Although the mean number of predisposing factors was greater among bacteremic patients than nonbacteremic patients, only alcohol ingestion was significantly more common. Nearly one-third of patients had substantial anemia (hemoglobin < or = 10 g/dL) on admission, which may have predisposed to infection. In the case of other laboratory abnormalities, such as albumin, creatinine, and bilirubin, it was difficult to determine which abnormality might have predisposed to pneumococcal infection and which might have resulted from it. The radiologic appearance was varied. Airspace consolidation and air bronchogram on chest X-ray were highly associated with bacteremic disease, as was the presence of pleural effusion. Although the Pneumonia Patient Outcomes Research Team (PORT) risk score was a predictor of mortality, it did not help to predict the presence of bacteremia in an individual case. Most patients who died in the first week in hospital were bacteremic, and a high PORT risk score with bacteremia reliably predicted a high likelihood of a fatal outcome. Eleven patients had extrapulmonary disease with meningitis, empyema, and septic arthritis predominating; all of these patients were bacteremic. The antibiotic susceptibility of our strains correlated well with those that have been reported in the United States during the years of this study. The use of numerous antibiotics of different classes in many patients, especially those who were the most ill, precluded analysis of outcome based on antibiotic therapy. Only 17 patients had been vaccinated. Since nearly all patients had conditions for which pneumococcal vaccine is recommended and more than one-third had been hospitalized in the preceding 6 months, the low rate of vaccination can be regarded as a missed opportunity to administer a potentially beneficial vaccine.

Screening for mutations of Bcl10 in leukaemia

The Bcl10 gene was identified through characterization of the t(1;14)(p22;q32) associated with mucosa-associated lymphoid tissue (MALT) lymphoma. Bcl10 is implicated in the regulation of apoptosis and has been reported to be mutated in other subtypes of non-Hodgkin's B-cell lymphoma (B-NHL) and leukaemic cell lines, raising the possibility that its deregulation could be implicated in other forms of haematological malignancy. We screened 226 cases, including 123 acute myeloid leukaemia (AML), 50 acute lymphoblastic leukaemia (ALL), 20 chronic myeloid leukaemia (CML), 10 chronic lymphocytic leukaemia-prolymphocytic leukaemia (CLL/PLL) and 23 cases with 1p abnormalities, for Bcl10 mutations by reverse transcription polymerase chain reaction-single-stranded conformation polymorphism (RT-PCR/SSCP). Three known polymorphisms and two common splice variants were identified; however, no mutations were detected. One splice variant led to a 33-bp in frame deletion, whereas the other caused a 16-bp deletion predicting C-terminal truncation of Bcl10. However, both splice variants were also detected in normal bone marrow, suggesting that they are unlikely to be of pathogenetic significance. Furthermore, Southern blot analysis revealed no rearrangements of Bcl10 among 16 ALL and 11 cases of haematological malignancy with 1p abnormalities. Our results suggest that mutation of the Bcl10 gene as a mechanism of tumorigenesis is not associated with leukaemia.

Identification of germline missense mutations and rare allelic variants in the ATM gene in early-onset breast cancer

Epidemiological studies have shown an increased risk of breast cancer in obligate ataxia telangiectasia (A-T) heterozygotes. We analyzed 100 samples from young breast cancer patients for mutations in ataxia-telangiectasia mutated (ATM), the gene responsible for the autosomal recessive condition, A-T, to determine whether A-T heterozygosity predisposes such individuals to develop breast cancer. These patients were selected from families with a moderate or absent family history of breast cancer and included a subset of 16 radiosensitive patients. Forty-four germline sequence variants were detected by fluorescent chemical cleavage of mismatch of RT-PCR products. These included seven rare variants found in nine patients (three described for the first time), but no truncating mutations. Although three variants were detected in the radiosensitive subset, this was not statistically significant compared to the nonradiosensitive group. One variant, G2765S, is likely to be a missense mutation, but the other six variants probably represent rare polymorphisms. However, five of the seven rare germline variants detected showed loss of heterozygosity of the wild-type ATM allele for one or more markers close to the ATM locus in matched tumor DNA. This high rate of somatic inactivation of ATM may indicate either that these rare variants play a role in breast cancer development or alternatively that a neighboring tumor suppressor gene is important for tumorigenesis. We found germline truncating ATM mutations to be rare in these young breast cancer patients and therefore they are unlikely to play a role in the etiology of their disease. Genes Chromosomes Cancer 26:286-294, 1999.

Presenting white blood cell count and kinetics of molecular remission predict prognosis in acute promyelocytic leukemia treated with all-trans retinoic acid: result of the Randomized MRC Trial

All-trans retinoic acid (ATRA) is an essential component of the treatment of acute promyelocytic leukemia (APL), but the optimal timing and duration remain to be determined. Molecular characterization of this disease can refine the diagnosis and could be potentially useful in monitoring response to treatment. Patients defined morphologically to have APL were randomized to receive a 5-day course of ATRA before commencing chemotherapy or to receive daily ATRA commencing with chemotherapy and continuing until complete remission (CR). The chemotherapy was that used in current MRC Leukaemia Trials. Outcome comparisons were by intention to treat with additional analysis for relevant risk factors. Patients were characterized by molecular techniques for the fusion products of the t(15;17) and monitored by reverse transcriptase-polymerase chain reaction (RT-PCR) during and after treatment. Two hundred thirty-nine patients were randomized. Treatment with extended ATRA resulted in a superior remission rate (87% v 70%, P <.001), due to fewer early and induction deaths (12% v 23%, P =.02), and less resistant disease (2% v 7%, P =.03), which was associated with a significantly more rapid recovery of neutrophils and platelets. Extended ATRA reduced relapse risk (20% v 36% at 4 years, P =.04) and resulted in superior survival (71% v 52% at 4 years, P =.005). Presenting white blood cell count (WBC) was a key determinant of outcome. The 70% of patients who presented with a WBC less than 10 x 10(9)/L had a better CR (85% v 62%, P =.0001) and reduced relapse risk (22% v 42%, P =.002) and superior survival (69% v 43%, P <. 0001). Within the low count group, extended ATRA resulted in a better CR (94% v 76%, P =.001), reduced relapse risk (13% v 35%, P =. 04), and improved survival (80% v 57%, P =.0009). There was no evidence of benefit in patients presenting with a higher WBC (>10 x 10(9)/L). Molecular monitoring after the third chemotherapy course had a correlation with risk of relapse. The relapse risk was 57% if the RT-PCR was positive versus 27% if the RT-PCR was negative (P =. 006). APL patients who present with a low WBC derive substantial benefit from combining ATRA with induction chemotherapy until remission is achieved, whereas patients with a higher WBC did not benefit. Molecular characterization of disease can improve diagnostic precision and a positive RT-PCR after consolidation identifies patients at a higher risk of relapse.

Risk factors for detecting germline BRCA1 and BRCA2 founder mutations in Ashkenazi Jewish women with breast or ovarian cancer

We ascertained 184 Ashkenazi Jewish women with breast/ovarian cancer (171 breast and 13 ovarian cancers, two of the former also had ovarian cancer) in a self-referral study. They were tested for germline founder mutations in BRCA1 (185delAG, 5382insC, 188del11) and BRCA2 (6174delT). Personal/family histories were correlated with mutation status. Logistic regression was used to develop a model to predict those breast cancer cases likely to be germline BRCA1/BRCA2 mutation carriers in this population. The most important factors were age at diagnosis, personal/family history of ovarian cancer, or breast cancer diagnosed before 60 years in a first degree relative. A total of 15.8% of breast cancer cases, one of 13 ovarian cancer cases (7.7%), and both cases with ovarian and breast cancer carried one of the founder mutations. Age at diagnosis in carriers (44.6 years) was significantly lower than in non-carriers (52.1 years) (p<0.001), and was slightly lower in BRCA1 than BRCA2 carriers. Thirty three percent of carriers had no family history of breast or ovarian cancer in first or second degree relatives. Conversely, 12% of non-mutation carriers had strong family histories, with both a first and a second degree relative diagnosed with breast or ovarian cancer. The predicted values from the logistic model can be used to define criteria for identifying Ashkenazi Jewish women with breast cancer who are at high risk of carrying BRCA1 and BRCA2 mutations. The following criteria would identify those at approximately 10% risk: (1) breast cancer <50 years, (2) breast cancer <60 years with a first degree relative with breast cancer <60 years, or (3) breast cancer <70 years and a first or second degree relative with ovarian cancer.

Rapid and efficient ATM mutation detection by fluorescent chemical cleavage of mismatch: identification of four novel mutations

Mutations in the Ataxia Telangiectasia Mutated (ATM) gene are responsible for the autosomal recessive disease Ataxia Telangiectasia (A-T). A wide variety of mutations scattered across the entire coding region (9168bp) of ATM have been found, which presents a challenge in developing an efficient mutation screening strategy for detecting unknown mutations. Fluorescent chemical cleavage of mismatch (FCCM) is an ideal mutation screening method, offering a non-radioactive alternative to other techniques such as restriction endonuclease fingerprinting (REF). Using FCCM, we have developed an efficient, accurate and sensitive mutation detection method for screening RT-PCR products for ATM mutations. We have identified seven ATM mutations in five A-T families, four of which are previously unknown. We quantified ATM protein expression in four of the families and found variable ATM protein expression (0-6.4%), further evidence for mutant ATM protein expression in both classic and variant A-T patients. We conclude that FCCM offers a robust ATM mutation detection method and can be used to screen for ATM mutations in cancer-prone populations.

Identification of the t(15;17) in AML FAB types other than M3: evaluation of the role of molecular screening for the PML/RARalpha rearrangement in newly diagnosed AML. The Medical Research Council (MRC) Adult Leukaemia Working Party

Acute promyelocytic leukaemia (APL) is characterized by the t(15;17) leading to the formation of PML-RARalpha and RARalpha-PML fusion genes; this rearrangement has been considered both diagnostic for, and restricted to, this subtype of acute myeloid leukaemia (AML FAB M3). We describe two cases of AML with the t(15;17) associated with a PML/RARalpha rearrangement which lacked typical APL morphology, classified as FAB M1 and M2 respectively. In both cases morphological review revealed small populations of cells which exhibited some features associated with APL. In the case classified as M1, PML immunofluorescence studies revealed the classic microparticulate nuclear staining pattern as observed in typical cases of APL with the t(15;17). Similarly, blasts from this case were found to be sensitive to ATRA in vitro as determined by NBT reduction test and by normalization of the PML nuclear body staining pattern. To determine the frequency of PML/RARalpha rearrangements in FAB subtypes other than M3, 530 patients from the MRC AML trials were screened using nested RT-PCR. Only one individual, initially classified as M5 with a normal karyotype, was found to have a PML/RARalpha rearrangement. The diagnosis was revised to M3 variant on subsequent morphological review. In conclusion, this study demonstrates that, in rare cases, the t(15;17) is not restricted to patients with M3 morphology as defined by current FAB criteria. Therefore, although we consider cytogenetic analysis of newly diagnosed cases of AML to be mandatory, our data suggests that routine molecular screening for PML/RARalpha rearrangements is not justified and should be reserved for those cases displaying features which may be suspicious of APL even if such cells comprise only a minority of the total population.

Methylation of the BRCA1 promoter region in sporadic breast and ovarian cancer: correlation with disease characteristics

Reduced expression of BRCA1 has been reported in sporadic breast cancer, although the mechanisms underlying this phenomenon remain unclear. Abnormal methylation leading to silencing of tumour suppressor genes has been implicated in tumorigenesis in a wide range of sporadic cancers. Therefore, we sought to determine the frequency of methylation within the BRCA1 promoter region in a large group of sporadic invasive breast (n =96) and ovarian (n = 43) carcinomas using Southern analyses. Overall, methylation was detected in 11% of breast cancer cases and in 5% of ovarian tumours. Methylation of the BRCA1 promoter region was strongly correlated with lack of estrogen and progesterone receptor expression. It is clear from the frequency of abnormal methylation of the BRCA1 promoter region, that this cannot be the sole mechanism mediating the reduced expression of BRCA1 that has previously been reported to occur in the majority of invasive sporadic breast tumours. Nevertheless this study suggests that abnormal methylation of the BRCA1 promoter may be important in tumorigenesis in a subset of sporadic breast and ovarian cancers.

SUMO-1 modification of the acute promyelocytic leukaemia protein PML: implications for nuclear localisation

PML is a nuclear phosphoprotein that was first identified as part of a translocated chromosomal fusion product associated with acute promyelocytic leukaemia (APL). PML localises to distinct nuclear multi-protein complexes termed ND10, Kr bodies, PML nuclear bodies and PML oncogenic domains (PODs), which are disrupted in APL and are the targets for immediate early viral proteins, although little is known about their function. In a yeast two-hybrid screen, we first identified a ubiquitin-like protein named PIC1 (now known as SUMO-1), which interacts and co-localises with PML in vivo. More recent studies have now shown that SUMO-1 covalently modifies a number of target proteins including PML, RanGAP1 and IkappaBalpha and is proposed to play a role in either targeting modified proteins and/or inhibiting their degradation. The precise molecular role for the SUMO-1 modification of PML is unclear, and the specific lysine residues within PML that are targeted for modification and the PML sub-domains necessary for mediating the modification in vivo are unknown. Here we show that SUMO-1 covalently modifies PML both in vivo and in vitro and that the modification is mediated either directly or indirectly by the interaction of UBC9 with PML through the RING finger domain. Using site-specific mutagenesis, we have identified the primary PML-SUMO-1 modification site as being part of the nuclear localisation signal (Lys487 or Lys490). However SUMO-1 modification is not essential for PML nuclear localisation as only nuclear PML is modified. The sequence of the modification site fits into a consensus sequence for SUMO-1 modification and we have identified several other nuclear proteins which could also be targets for SUMO-1. We show that SUMO-1 modification appears to be dependant on the correct subcellular compartmentalisation of target proteins. We also find that the APL-associated fusion protein PML-RARA is efficiently modified in vitro, resulting in a specific and SUMO-1-dependent degradation of PML-RARA. Our results provide significant insights into the role of SUMO-1 modification of PML in both normal cells and the APL disease state.

Identification of a C/G polymorphism in the promoter region of the BRCA1 gene and its use as a marker for rapid detection of promoter deletions

Reduced expression of BRCA1 has been implicated in sporadic breast cancer, although the mechanisms underlying this phenomenon remain unclear. To determine whether regulatory mutations could account for the reduced expression, we screened the promoter region by sequencing in 20 patients with sporadic disease. No mutations were detected; however, a new polymorphism consisting of a C-to-G base change within the beta-promoter was identified, with the frequency of the G allele being 0.34. Close to complete linkage disequilibrium was found between this marker and the Pro871 Leu polymorphism, situated in exon 11, which has previously been shown not to be associated with breast or ovarian cancer. This indicates that the C/G polymorphism is also unlikely to play a role in either disease. However, the strength of linkage disequilibrium between these markers permitted their use for rapid screening for genomic deletions within BRCA1. A series of 214 cases with familial breast cancer were analysed using this approach; 88/214 were heterozygous for the promoter polymorphism, thereby excluding a deletion in this region. Among the remaining patients, one hemizygous case reflecting a promoter deletion was successfully identified. Therefore, this study indicates that deletions within the beta-promoter region of BRCA1 are an uncommon event in familial breast cancer. Furthermore, it suggests that mutations within the BRCA1 promoter are unlikely to account for the reported decreased expression of BRCA1 in sporadic disease.

Truncated TSG101 transcripts are present in peripheral blood from both familial breast cancer patients and controls

TSG101 is a recently identified putative tumour suppressor gene which has been implicated in human breast cancer. To address whether germline disruption of TSG101 predisposes individuals to this disease, we analysed genomic DNA and mRNA isolated from peripheral blood from 20 familial breast cancer cases. No evidence of large intragenic insertions/deletions or point mutations in TSG101 was found by Southern blot analysis and sequence analysis of the entire coding region. However, in 11 of 20 samples, 'aberrant' transcripts were detected. Sequence analysis suggested that these variants were generated by the use of different cryptic splicing sites. Such alternative/aberrant splicing events were not restricted to cancer patients, but were also detected in peripheral blood of non-cancer patients and in normal tissues.

Identification of missense and truncating mutations in the BRCA1 gene in sporadic and familial breast and ovarian cancer

The cloning of the breast and ovarian cancer susceptibility gene, BRCA1, allows direct estimation of the proportion of these cancers in the general population which can be attributed to germline mutations in this gene. We have used a combination of SSCP, heteroduplex analysis, and chemical cleavage of mismatch to screen the BRCA1 gene for mutations in the germline of 42 patients with breast or ovarian cancer who either have a moderate family history of these cancers, or have no family history of malignancy but a very early onset of the disease. A total of 30 sequence variants were observed, eight of which have not been described previously. Three sequence changes detected by chemical cleavage or heteroduplex analysis were missed by SSCP. The variants included 13 missense mutations, which were assessed for their pathogenic implications. Two of these (M18T and A1708E) are nonconservative substitutions which are located in evolutionarily conserved regions of the gene: M18T lies just upstream of the RING finger motif, and A1708E abolishes the transcriptional transactivation activity of the carboxy-terminal region of BRCA1. Mutations were observed in eight patients overall (19.0%), and protein-truncating mutations occurred in five of 27 (18.5%) families with 1-3 cases of breast or ovarian cancer. The data suggest that a significant proportion of patients with a modest or no family history of these cancers may carry germline mutations in BRCA1.

The ubiquitin-homology gene PIC1: characterization of mouse (Pic1) and human (UBL1) genes and pseudogenes

The human ubiquitin-homology domain protein PIC1 interacts with the acute promyelocytic leukemia protein PML, and both proteins form part of the large, nuclear, multiprotein complexes known as PML nuclear bodies. The normal punctate immunohistochemical staining pattern of these complexes is disrupted by viral infection or interferon treatment and in blast cells from patients with acute promyelocytic leukemia. We have characterized the murine homologue of PIC1 and have found that the predicted amino acid sequences of the mouse and human proteins are identical. High levels of Pic1 mRNA were detected in a range of mouse tissues. Pic1 genomic clones were isolated, and the organization of the gene was determined. Two processed Pic1 pseudogenes were also isolated and characterized. Through FISH, the chromosomal localizations of the mouse Pic1 gene and the two pseudogenes were determined. Human PIC1 (HGMW-approved symbol UBL1)-related sequences were isolated from human genomic DNA and were shown to represent processed pseudogenes. The role of PIC1 in a variety of cellular processes is discussed.

Characterization of cryptic rearrangements and variant translocations in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is typified by the reciprocal translocation, t(15; 17)(q22; q21), leading to the formation of PML-RARalpha and RARalpha-PML fusion genes. We have characterized 7 cases of morphologic APL found to lack the t(15; 17) on conventional cytogenetic assessment. In 6 of 7 cases, cryptic PML-RARalpha rearrangements were identified by reverse transcriptase-polymerase chain reaction and fluorescent in situ hybridization (FISH); whereas, in the remaining patient, APL was associated with the variant translocation, t(11; 17)(q23; q12-21), leading to the formation of PLZF-RARalpha and RARalpha-PLZF fusion genes. In each of the cases with cryptic PML-RARalpha rearrangements, PML-RARalpha transcripts were detected in the absence of RARalpha-PML, consistent with the concept that PML-RARalpha is the critical oncogenic fusion protein. In 4 of these cases with evaluable metaphase spreads, the occurrence of a nonreciprocal translocation was confirmed by FISH with sole formation of the PML-RARalpha fusion gene; in 3 cases with morphologically normal chromosomes 15 and 17, RARalpha was inserted into PML on 15q, whereas in the remaining patient the PML-RARalpha fusion arose due to insertion of 15q-derived material including PML into RARalpha on 17q. Immunofluorescence studies were performed using antibodies raised against PML and PIC 1, a ubiquitin-homology domain protein previously identified as an interaction partner of PML. In acute myeloid leukemia (AML) of subtypes other than M3, PIC 1 was localized to the nuclear membrane and colocalized with PML within discrete nuclear bodies. In APL cases with cryptic PML-RARalpha rearrangements, the characteristic microparticulate pattern of PML staining was detected with partial colocalization with PIC 1, indicative of disruption of the nuclear bodies; whereas in t(11; 17)-associated APL, PML and PIC 1 remained colocalized within discrete nuclear bodies, as observed in non-APL cases. Although deregulation of the putative growth suppressor PML and delocalization of other nuclear body constituents have been advocated to play a key role in the development of t(15; 17)-associated APL, the present study shows that disruption of PML nuclear bodies per se is not a prerequisite for the pathogenesis of APL.

Intrathecal fentanyl with small-dose dilute bupivacaine: better anesthesia without prolonging recovery

Recent concern regarding lidocaine neurotoxicity has prompted efforts to find alternatives to lidocaine spinal anesthesia. Small-dose dilute bupivacaine spinal anesthesia yields a comparably rapid recovery profile but may provide insufficient anesthesia. By exploiting the synergism between intrathecal opioids and local anesthetics, it may be possible to augment the spinal anesthesia without prolonging recovery. Fifty patients undergoing ambulatory surgical arthroscopy were randomized into two groups receiving spinal anesthesia with 3 ml 0.17% bupivacaine in 2.66% dextrose without (Group I) or with (Group II) the addition of 10 microg fentanyl. Median block levels reached T7 and T8, respectively (P = not significant [NS]). Mean times to two-segment regression, S2 regression, time out of bed, time to urination, and time to discharge were 53 vs 67 min (P < 0.01), 120 vs 146 min (P < 0.05), 146 vs 163 min (P = NS), 169 vs 177 min (P = NS), and 187 vs 195 min (P = NS) respectively. Motor blockade was similar between groups, but sensory blockade was significantly more intense in Group II (P < 0.01). Six of 25 blocks failed in Group I, whereas none failed in Group II. The addition of 10 microg fentanyl to spinal anesthesia with dilute small-dose bupivacaine intensifies and increases the duration of sensory blockade without increasing the intensity of motor blockade or prolonging recovery to micturition or street fitness.

IMPLICATIONS

Concerns about the neurotoxicity of lidocaine have prompted efforts to find alternatives to lidocaine spinal anesthesia. We studied 50 patients undergoing ambulatory surgical arthroscopy and found that although small-dose bupivacaine alone is inadequate for this procedure, the addition of fentanyl makes it reliable.

Complex regulation of the BRCA1 gene

We have analyzed the promoter region of the human BRCA1 gene in detail and demonstrate that the expression of the BRCA1 gene is under complex regulation. First, its transcription is under the control of two promoters generating two distinct transcripts alpha and beta, and second, promoter alpha is shared with the adjacent NBR2 gene and is bi-directional. Both promoter alpha and promoter beta are responsive to estrogen stimulation. We also discerned that there are striking differences in both the genomic organization and immediate cis-control elements of the BRCA1 gene between humans and mice.

Isolation and characterisation of the NBR2 gene which lies head to head with the human BRCA1 gene

To study the regulation of BRCA1 gene expression and the potential importance of dysregulation of this gene in breast and ovarian cancer, we have examined the 5' region of the human BRCA1 gene in detail. We have identified a new gene, NBR2, which is partially related to the NBR1 gene (formerly known as 1A1-3B and mapping directly adjacent to the pseudo-BRCA1 gene) and which lies head to head with the BRCA1 gene. The physical distance between the transcription start sites of the NBR2 and BRCA1 genes is 218 bp, suggesting that regulation of the expression of both genes may be co-ordinated through a bi-directional promoter. The NBR2 gene contains five exons spanning a genomic region of approximately 30 kb between the BRCA1 and pseudo-BRCA1 genes. Northern analysis showed that the NBR2 gene is expressed in all the tissues examined. The NBR2 cDNA contains an open reading frame of 112 amino acids and is predicted to encode a protein of approximately 12 kDa. Single-strand conformation polymorphism (SSCP) analysis of the NBR2 gene failed to identify any mutations in either breast or ovarian cancer, suggesting that if the NBR2 gene is involved in the development of these cancers, other mechanisms for tumorigenesis may exist. Hybridisation of NBR2 probes to zoo blots showed that the NBR2 gene is present in human and other primates. No hybridisation to DNA from other species was observed, suggesting that genomic elements controlling BRCA1 expression may differ between species.

Studies on inherited cancers: outcomes and challenges of 25 years

Research on the dominantly inherited cancer-susceptibility syndromes over the past 25 years has defined the genetic basis of most of these diseases, usually through linkage analysis on families carrying the disease, and identification and analysis of the genes responsible. At present, almost all of these genes have been cloned and, in most cases, the findings have lent full support to Knudson's original hypothesis: germline carriers of mutations in cancer susceptibility genes are predisposed to developing cancer, the resultant tumours contain aberrations in the remaining copy of that gene, and these genes often play a pivotal role in the genesis of the equivalent sporadic cancers, whereby two somatic events result in the disruption of both copies of the gene. This perspective highlight some of the issues that have been raised by these studies, and points to a few of the areas of future research that might help to resolve them.

Clinical and molecular features of the hereditary mixed polyposis syndrome

BACKGROUND & AIMS

Various inherited syndromes predispose to the development of colonic juvenile polyps and colorectal cancer, with potential importance for sporadic tumorigenesis. This study describes features of a possibly new syndrome of atypical juvenile polyps and other colonic tumors and compares these features with those of known gastrointestinal tumor syndromes.

METHODS

A large family, St. Mark's family 96, with a tendency to develop colonic polyps of mixed histological types is described. Genetic linkage to known polyposis syndromes has been tested.

RESULTS

Adenomatous and hyperplastic polyps occur in affected members of the family, although the characteristic lesion is an atypical juvenile polyp. Some affected individuals have developed polyps of more than one type, and individual polyps may contain features of more than one histological type. Polyps can undergo malignant change. Typically, fewer than 15 polyps are found at colonoscopy and there is no extracolonic disease associated with the development of polyps. The family's polyps seem to be inherited in an autosomal-dominant fashion, but the disease is probably unlinked to candidate loci with importance in colorectal tumorigenesis, such as APC, hMSH2, and hMLH1.

CONCLUSIONS

We term this family's disease hereditary mixed polyposis syndrome (HMPS). Although mutations in the putative HMPS gene may be responsible for syndromes such as juvenile and Peutz-Jeghers polyposes, HMPS may also be a distinct disease.

Mutations and alternative splicing of the BRCA1 gene in UK breast/ovarian cancer families

BRCA1 is a tumour suppressor gene located on chromosome band 17q21. It is estimated that mutations in the BRCA1 gene account for approximately 45% of the breast cancer families and almost all of the breast/ovarian cancer families. We have used single strand conformation polymorphism analysis, direct sequencing, allele specific oligonucleotide hybridisation, and reverse transcription polymerase chain reaction (RT-PCR) to look for mutations in the BRCA1 gene in 49 breast or breast/ovarian cancer families. Five distinct mutations, three novel and two previously observed, were detected in seven families. Each novel mutation was identified in one family: 3896delT in exon 11, a splicing mutation in the intron 9-exon 10 junction, and an inferred regulatory mutation. The 185delAG in exon 2 was found in three families sharing the same haplotype, but this haplotype is different from that shared by the Ashkenazi Jewish families, suggesting that the 185delAG in our families may have arisen independently. Another previously reported mutation, the 3875del4 in exon 11, was identified in one family. Of the 49 families examined, linkage analyses for both the BRCA1 and the BRCA2 regions were performed on 33 families, and mutations in the BRCA1 gene were identified in all but one family that have a lod score above 0.8 for BRCA1. All of the mutations cause either a truncated BRCA1, or loss of a BRCA1 transcript, thus are likely to be functionally disruptive. In addition, we found that alternative splicing is a common phenomenon in the processing of the BRCA1 gene. Seven variant BRCA1 transcripts were identified by RT-PCR; all but one maintained the BRCA1 open reading frame. We believe that alternative splicing may play a significant role in modulating the physiological function of BRCA1.

Characterisation of the PML/RAR alpha rearrangement associated with t(15;17) acute promyelocytic leukaemia

The vast majority of cases of APL are associated with t(15; 17) leading to the formation of PML-RAR alpha, RAR alpha-PML and aberrant PML fusion products. PML-RAR alpha is invariably transcribed and is believed to mediate leukaemogenesis. PML was initially considered to be a transcription factor. However, characterisation of other RING finger containing proteins shows no direct evidence for DNA binding. The RING, B-box, and coiled-coil domains are more likely to represent sites of protein-protein interaction and may be critical for the stability of the multiprotein nuclear domains of which PML is an integral part. In APL the nuclear bodies become disrupted, presumably as a consequence of the presence of PML-RAR alpha and aberrant PML proteins that might render the structure unstable. PML-RAR alpha is capable of binding RXR and sequestering it into the disrupted nuclear domains. Sequestration of RXR would be expected to limit high affinity binding of VDR, TR and residual RARs to DNA response elements and might account for the block in myeloid differentiation at the promyelocyte stage that characterizes APL. Recently PML has been found to have growth suppressor/anti-oncogenic activity. It is unclear whether this is a property of PML itself or reflects a nonspecific function of the PML-associated nuclear domains. Hence the PML/RAR alpha rearrangement alone may be sufficient to cause APL. Abnormal PML function may prevent its growth-suppressor activity, leading to leukaemic transformation; concomitant disruption of retinoid pathways due to sequestration of RXR and/or an abnormal repertoire and character of response element activation mediated by the fusion protein, causing the block in myeloid differentiation (Fig. 3). Disruption of RAR alpha would be expected to account for the similar leukaemic phenotype associated with the t(5;17) and t(11;17) APL cytogenetic variants. Further characterisation of NPM and PLZF at the structural and functional level will determine whether PML and other proteins disrupted in APL associated translocations play an active or purely permissive role in leukaemogenesis and will help dissect the events leading to transformation from those causing blockade of myeloid differentiation and mediating the response to ATRA.