Comprehensive screening for constitutional RB1 mutations by DHPLC and QMPSF

Constitutional mutations of the RB1 gene are associated with a predisposition to retinoblastoma. It is essential to identify these mutations to provide appropriate genetic counseling in retinoblastoma patients, but this represents an extremely challenging task, as the vast majority of mutations are unique and spread over the entire coding sequence. Since 2001, we have implemented RB1 testing on a routine basis as part of the clinical management of retinoblastoma. As most screening techniques do not meet the requirements for efficient RB1 testing, we have devised a semi-automated denaturing high-performance liquid chromatography (DHPLC) method for point mutation detection combined with a quantitative multiplex PCR of short fluorescent fragments (QMPSF) approach to screen for gene rearrangements. We report the results of this comprehensive screening of all exons and promoter of RB1 in 192 unrelated patients, mostly of French origin. Among 102 bilateral and/or familial cases and 90 unilateral sporadic probands, mutations were identified in 83 (81.5%) and 5 (5.5%) cases, respectively. A total of 43 mutations have not been previously reported. The mutational spectrum was found to be significantly different from previous published series, displaying a surprising amount of splice mutations and large deletions. This study demonstrates the reliability of DHPLC for RB1 analysis, but also illustrates the need for a deletion scanning approach. Finally, considering the benefits to retinoblastoma patients, RB1 testing should be widely implemented in routine healthcare because our study clearly illustrates its feasibility.

Quality assessment of genetic markers used for therapy stratification

PURPOSE

Therapy stratification based on genetic markers is becoming increasingly important, which makes commitment to the highest possible reliability of the involved markers mandatory. In neuroblastic tumors, amplification of the MYCN gene is an unequivocal marker that indicates aggressive tumor behavior and is consequently used for therapy stratification. To guarantee reliable and standardized quality of genetic features, a quality-assessment study was initiated by the European Neuroblastoma Quality Assessment (ENQUA; connected to International Society of Pediatric Oncology) Group.

MATERIALS AND METHODS

One hundred thirty-seven coded specimens from 17 tumors were analyzed in 11 European national/regional reference laboratories using molecular techniques, in situ hybridization, and flow and image cytometry. Tumor samples with divergent results were re-evaluated.

RESULTS

Three hundred fifty-two investigations were performed, which resulted in 23 divergent findings, 17 of which were judged as errors after re-evaluation. MYCN analyses determined by Southern blot and in situ hybridization led to 3.7% and 4% of errors, respectively. Tumor cell content was not indicated in 32% of the samples, and 11% of seemingly correct MYCN results were based on the investigation of normal cells (eg, Schwann cells). Thirty-eight investigations were considered nonassessable.

CONCLUSION

This study demonstrated the importance of revealing the difficulties and limitations for each technique and problems in interpreting results, which are crucial for therapeutic decisions. Moreover, it led to the formulation of guidelines that are applicable to all kinds of tumors and that contain the standardization of techniques, including the exact determination of the tumor cell content. Finally, the group has developed a common terminology for molecular-genetic results.

Agreement between chromogenic in situ hybridisation (CISH) and FISH in the determination of HER2 status in breast cancer

Determination of the HER2/neu (HER2) status in breast carcinoma has become necessary for the selection of breast cancer patients for trastuzumab therapy. Amplification of the gene analysed by fluorescence in situ hybridisation (FISH) or overexpression of the protein determined by immunohistochemistry (IHC) are the two major methods to establish this status. A strong correlation has been previously demonstrated between these two methods. However, FISH is not always feasible in routine practice and weakly positive IHC tumours (2+) do not always correspond to a gene amplification. Our study was performed in order to evaluate the contribution of chromogenic in situ hybridisation (CISH), which enables detection of the gene copies through an immunoperoxidase reaction. CISH was performed in 79 breast carcinomas for which the HER2 status was previously determined by IHC and FISH. The results of IHC, FISH and CISH were compared for each tumour. CISH procedures were successful in 95% of our cases. Whatever the IHC results, we found a very good concordance (96%) between CISH and FISH. Our study confirms that CISH may be an alternative to FISH for the determination of the gene amplification status in 2+ tumours. Our results allow us to think that, in many laboratories, CISH may also be an excellent method to calibrate the IHC procedures or, as a quality control test, to check regularly that the IHC signal is in agreement with the gene status.

Calibration of immunohistochemistry for assessment of HER2 in breast cancer: results of the French multicentre GEFPICS study

AIMS

HER2 protein is over-expressed in 15-30% of breast carcinomas. Immunohistochemistry (IHC) is a common and inexpensive method able to specifically detect HER2 protein. However, lack of standardization of IHC has been considered responsible for discrepancies in HER2 status assessment performed by IHC and fluorescence in-situ hybridization (FISH). This prompted us to perform a multicentric IHC calibration test to achieve a maximum accuracy of HER2-IHC compared with HER2-FISH taken as the reference method.

METHODS AND RESULTS

Twelve French laboratories participated in this study, including 119 cases of invasive breast carcinomas for which both fixed and frozen tissues were available. HER2 expression was determined in fixed tissues by individual in-house IHC techniques, using either CB11 (Novocastra, Newcastle, UK) or A0485 (Dako, Glostrup, Denmark) anti-HER2 antibodies. Two cut-off values were used: 10% and 60% of immunostained cells. In 116 of the 119 cases, HER2 gene status could also be determined by FISH on frozen sections, performed in a single laboratory. Results were centralized and compared. When suboptimal concordance between IHC and FISH was observed, IHC was calibrated and a second run was performed. The specificity, sensitivity and accuracy of IHC compared with FISH were noted before and after calibration. Forty-four out of 116 (38%) tumours showed HER2 gene amplification. Accuracy of IHC was complete in the first run for 6/12 laboratories. Calibration, necessary for the six others, relied mainly on the combination of a heat-induced epitope retrieval step with an increase of dilution of the primary antibody. In the second run, HER2 over-expression was found in 46 (40%) and 44 (38%) of the 116 cases, using 10% or 60% of stained cells as cut-offs, respectively. The corresponding accuracy rates were 93% and 95%.

CONCLUSIONS

This study showed that a high accuracy of IHC could be obtained for the determination of HER2 status in all laboratories using their in-house IHC technique, provided that a calibration process was performed. Antigen retrieval procedure, high dilutions of anti-HER2 antibody and the use of specific controls were crucial for HER2-IHC calibration. A 95% accuracy rate of IHC, using FISH as gold standard, was obtained by considering immunolabelling HER2-IHC results as a continuous variable, and taking 60% invasive stained cells as the cut-off for HER2 over-expression.

Steroid-induced mania in an adolescent: risk factors and management

Few studies have clearly defined the risk factors and management of steroid-induced mania, particularly in children and adolescents. The case study of a 15-year-old woman with steroid-induced mania is examined to delineate risk factors and management. Genetic predisposition to mood disorders, previous exposure to steroids and the concomitant use of clarithromycin are potential risk factors. Mood stabilizers such as lithium and/or valproic acid may be useful in the acute and prophylactic treatment of steroid-induced mania.

Bilateral renal oncocytosis with renal failure

Oncocytosis is a term recently used to describe diffuse renal involvement by numerous oncocytic nodules. We report herein a case of a 53-year-old man with end-stage renal disease requiring hemodialysis. His kidneys were involved by numerous tumors. Histologic examination revealed more than 100 oncocytomas and an associated papillary renal cell carcinoma in the right kidney.

Strong correlation between results of fluorescent in situ hybridization and immunohistochemistry for the assessment of the ERBB2 (HER-2/neu) gene status in breast carcinoma

ERBB2 (HER-2/neu) amplification and/or overexpression are associated with poor prognosis in node-positive breast carcinoma. Its prognostic value in node-negative cases and its predictive value for response to chemotherapy remain controversial. This may be related to the use of molecular methods, which are sensitive to dilution of tumor material by normal cells, or the use of nonstandardized immunohistochemistry (IHC) procedures, for the determination of the ERBB2 gene status. In addition, new therapeutic approaches that target the cells overexpressing ERBB2 are under development. These perspectives necessitate a reliable evaluation of the status of ERBB2 in individual tumors before the application of specific therapeutic strategies. Fluorescent in situ hybridization (FISH) and IHC allow the evaluation of the ERBB2 status specifically in tumor cells on archival material. We have analyzed a series of 100 invasive ductal breast carcinomas without lymph node invasion both by IHC, using the CB11 monoclonal antibody and a sensitive Auidin Biotin Complex (ABC) immunodetection system, and by FISH, using the Oncor Inform HER-21neu (ERBB2) gene amplification detection system as reference technique. Complete concordance between the results of FISH and IHC was seen in 98% of the cases. ERBB2 amplification (more than four signals per nucleus) was observed in 12 of the 100 cases, and all but one showed an overexpression of the protein (membrane staining) by IHC. Conversely, ERBB2 expression was present in one case without gene amplification. In conclusion, ERBB2 overexpression detected by IHC is highly correlated to gene amplification detected by FISH. Thus, under standardized conditions, IHC is a reliable and economical test to assess the ERBB2 status in tumors. The use of FISH could be limited to the verification of the status of tumors displaying a weak membrane immunostaining.

Establishment of a human malignant fibrous histiocytoma cell line, COMA. Characterization By conventional cytogenetics, comparative genomic hybridization, and multiplex fluorescence In situ hybridization

The human COMA cell line has been established from a storiform pleomorphic malignant fibrous histiocytoma (MFH). As expected for this tumor type, a very complex karyotype was observed after R-banding analysis. An extensive analysis by 24-color painting, comparative genomic hybridization (CGH), and fluorescence in situ hybridization (FISH) was performed. Twelve complex marker chromosomes recurrently observed were clearly identified; among them, three were systematically present in all analyzed metaphases. Amplifications detected by CGH were refined by FISH with probes specific for various candidate loci. A significant aneuploidy and numerous micronuclei were observed, which could be related to the anomalies of centriole numbers detected in a proportion of cells. Such an analysis, performed on a series of MFH cell lines, would allow the delineation of the genomic alterations specific for the oncogenesis or progression of this complex tumor type or both.

Detection of chromosome imbalances in retinoblastoma by parallel karyotype and CGH analyses

We have studied a series of 20 primary retinoblastomas by karyotypic analysis and comparative genomic hybridization (CGH), to perform an exhaustive evaluation of chromosome imbalances in this tumor. In addition, 4 tumors were studied by CGH only. On the whole, CGH results were largely in agreement with those of karyotypic analysis and with known cytogenetic data. The most frequent imbalances were +6p (13/24 cases), +1q (12/24), -16/-16q (11/24), and +2p (9/24). Recurrent high-level amplifications were observed in 2p23-25 and 1q21. Amplification of 2p23-25, present in 4 cases among which 3 showed double-minute chromosomes, was related to MYCN amplification, as demonstrated by FISH and PCR. No evident correlation was found in this small series between any of the imbalances identified and either the differentiation or the histoprognostic risk.

Detection and quantitation by fluorescence in situ hybridization (FISH) and image analysis of HER-2/neu gene amplification in breast cancer fine-needle samples

BACKGROUND

Fine-needle sampling, although a practical and noninvasive method of tissue acquisition, has rarely been used for HER-2/neu fluorescent in situ hybridization (FISH). To assess HER-2/neu gene amplification in mammary carcinoma, FISH signals on cytology and corresponding tissue biopsies were detected visually and measured by image analysis. The results were correlated with patient and tumor characteristics.

METHODS

In situ HER-2/neu DNA probe hybridization was performed on 61 cytology specimens and on 47 corresponding frozen sections of breast carcinomas. Tumors were classified by visual evaluation as unamplified, moderately amplified, or highly amplified. Multiparametric image analysis was performed using the Discovery automated image analyzer (Becton Dickinson, Leiden, Netherlands). The integrated fluorescence ratio (IFR) was calculated for each sample as the integrated FISH fluorescence of the tumor cells divided by the integrated FISH fluorescence of internal control cells containing two spots. The percentage positive nuclear area (PPN), calculated as the area of FISH fluorescence divided by the area of nuclear DNA fluorescence, and the PPR, ratio of the PPN of the tumor cells divided by the control cells, were also calculated for each sample.

RESULTS

Visual analysis yielded 46 unamplified and 15 (24.6%) amplified (seven moderately amplified and eight highly-amplified) tumors. Strong (P < 0.001) correlation between results on cytological and histological materials was obtained. The FISH spots on the cytological preparations were more easily visualized and scored than those on the corresponding tissue sections. Visual HER-2/neu signal scoring was strongly correlated with IFR (P = 0.0001) and PPR (P = 0.0001). Within the tumors classified as highly amplified by visual examination, quantitation of the degree of amplification fluorescence signal was possible using image analysis.

CONCLUSIONS

Cytologic specimens were a suitable and representative source of materials for detection and quantitation of HER-2/neu gene amplification by FISH and image analysis. Cancer (Cancer Cytopathol)

Cytogenetic study of eight new cases of radiation-induced solid tumors

Radiation-induced tumors were selected according to the criteria defined by Cahan (1948) for sarcomas. Cell cultures and/or xenografts in nude mice were performed with biopsies obtained from second primary tumors. Karyotypes of eight tumors were established after R-banding. After comparison with literature data on 15 other cases, two distinct cytogenetic patterns could be distinguished. One was characterized by polyclonal karyotypes, of which a large proportion were simple and carriers of balanced translocations. Another one was characterized by monoclonal chromosome alterations observed in highly aneuploid and complex karyotypes, in which many deletions were observed. These two different patterns could be related to the modality of metaphase harvesting. Polyclonal karyotypes were preferentially observed after long-term cultures, and monoclonal karyotypes after short-term cultures or xenografts. The following scheme of radiation oncogenesis is proposed: a) induction of recessive gene mutations including that of tumor suppressor genes; b) accumulation of genomic alterations in the irradiated tissue with aging, including deletions or mutations of normal alleles from mutated tumor suppressor genes; and c) loss of tumor suppressor gene function and initiation of a multistage tumor development and progression. Polyclonal abnormalities are assumed to exist in noncancerous cells which acquired radiation-induced chromosome aberrations.

[Renal medullary carcinoma, a new clinico-pathological entity. Immunohistochemical, ultrastructural, flow cytometric and cytogenetic study of a case]

The renal medullary carcinoma is a rare tumor. We report a case in a black patient with sickle cell trait. The tumor was located in the lower pole of the left kidney. It had a tubular and microcystic architecture. It was composed of large eosinophilic cells with vesicular nuclei containing prominent nucleoli, in a desmoplastic and inflammatory stroma. By immunohistochemistry, the tumoral cells were positive for cytokeratin and Ulex europaeus lectin. Electron microscopy revealed small intracytoplasmic lumina with microvilli. The flow cytometric study showed DNA-multiploidy. The cytogenetic study revealed tetraploidy without structural abnormality. The renal medullary carcinoma is often reported in young black patients with sickle cell trait. Its microscopic, immunohistochemical and ultrastructural features favor its identification as a particular variety of Bellini duct carcinoma. Its link with sickle cell trait has to be defined.

A possible tetracycline-risperidone-sertraline interaction in an adolescent

A 15-year-old adolescent male, with Asperger's disorder, Tourette's disorder and obsessive-compulsive disorder, on a tetracycline-risperidone-sertraline treatment regimen, had an acute exacerbation of motor and vocal tics. The increase in tics may have resulted from either a tetracycline-risperidone interaction leading to decreased levels of risperidone, or a tetracycline-sertraline interaction leading to increased levels of sertraline or the natural course of the Tourette's disorder. The sertraline dose was increased with no concomitant increase in tics, and subsequent discontinuation of tetracycline resulted in an improvement in tics, which indicates an interaction between tetracycline and risperidone. The addition of antibiotics to psychotropic medications requires close monitoring due to the potential interactions.

Interleukin 17, a T-cell-derived cytokine, promotes tumorigenicity of human cervical tumors in nude mice

Interleukin (IL) 17 is a proinflammatory cytokine secreted mainly by activated human memory CD4 T cells that induces IL-6, IL-8, and nitric oxide. Because IL-6 and IL-8 have been implicated in the pathogenesis of cervical cancer, we investigated the action of IL-17 on human cervical tumor cell lines in vitro and in vivo. We showed that in vitro, IL-17 increases IL-6 and IL-8 secretion by cervical carcinoma cell lines at both protein and mRNA levels. No direct effect of IL-17 on in vitro proliferation of cervical tumor cell lines could be demonstrated. However, two cervical cell lines transfected with a cDNA encoding IL-17 exhibited a significant increase in tumor size as compared to the parent tumor when transplanted in nude mice. This enhanced tumor growth elicited by IL-17 was associated with increased expression of IL-6 and macrophage recruitment at the tumor site. A potential role of IL-17 in modulation of the human cervical tumor phenotype was also supported by its expression on the cervical tumor in patients with CD4 infiltration. IL-17 therefore behaves like a T-cell-specific cytokine with paradoxical tumor-promoting activity. This may partially explain previous reports concerning the deleterious effect of CD4 T cells in cancer.

hSNF5/INI1 inactivation is mainly associated with homozygous deletions and mitotic recombinations in rhabdoid tumors

The chromatin-remodeling hSNF5/INI1 gene has recently been shown to act as a tumor suppressor gene in rhabdoid tumors (RTs). In an attempt to further characterize the main chromosomal mechanisms involved in hSNF5/INI1 inactivation in RTs, we report here the molecular cytogenetic data obtained in 12 cell lines harboring hSNF5/INI1 mutations and/or deletions in relation to the molecular genetic analysis using polymorphic markers extended to both extremities of chromosome 22q. On the whole, mitotic recombination occurring in the proximal part of chromosome 22q, as demonstrated in five cases, and nondisjunction/duplication, highly suspected in two cases (processes leading respectively to partial or complete isodisomy), appear to be major mechanisms associated with hSNF5/INI1 inactivation. Such isodisomy accompanies each of the RTs exhibiting two cytogenetically normal chromosomes 22. This results in homozygosity for the mutation at the hSNF5/INI1 locus. An alternate mechanism accounting for hSNF5/INI1 inactivation observed in these tumors is homozygous deletion in the rhabdoid consensus region. This was observed in each of the four tumors carrying a chromosome 22q abnormality and, in particular, in the three tumors with chromosomal translocations. Only one case of our series illustrates the mutation/deletion classical model proposed for the double-hit inactivation of a tumor suppressor gene.

[Herceptin, a monoclonal humanized antibody anti-HER2: a major therapeutic progress in breast cancers overexpressing this oncogene?]

HER2 is overexpressed in about 25% to 30% of breast cancers and associated with poor prognosis, resistance to hormonotherapy and lack of sensitivity to CMF-based adjuvant chemotherapy. Herceptin (trastuzumab), a humanized monoclonal antibody, administered as a single agent, produces objective responses in phase II trials in patients with metastatic breast cancers overexpressing HER2. It has shown a substantial benefit in a phase III trial which compares a standard first line chemotherapy (doxorubicin and cyclophosphamide or taxol alone) to the same chemotherapy with Herceptin in metastatic breast cancer. The Herceptin arm had significantly higher response rate (+ 53%), an improvement in the median duration of response (+ 57%) as well as in time to progression (+ 65%) compared to chemotherapy alone.

Two new cases of papillary renal cell carcinoma with t(X;1)(p11;q21) in females

Two cases of papillary renal cell carcinoma (RCC) with a karyotype 46,X,t(X;1)(p11.2;q21) in two female patients aged 9 and 29 years are reported. These observations, and the review of the 17 reported cases with a translocation at band Xp11 confirm that this abnormality delineates a clinicopathological entity within the classical papillary RCC, characterized by the early age of occurrence and, probably, distinct histological features. Including these two new female cases, the sex ratio in cases with t(X;1) appears similar to that observed in the other papillary RCC.

Mechanisms of acid-base regulation in migrant sea lampreys (Petromyzon marinus) following exhaustive exercise

The life cycle of the sea lamprey (Petromyzon marinus) is characterized by a terminal upstream spawning migration that may be associated with brief bursts of high-intensity swimming. Such activity usually leads to pronounced blood acid-base disturbances in fishes, but lampreys rapidly correct these perturbations within 1 h. In the present study, patterns of post-exercise H+ excretion (JHnet) and ion movements were followed in sea lampreys to test the hypothesis that dynamic manipulation of Na+ versus Cl- movements across the animal's body surface, presumably at the gills, accounted for the rapid restoration of blood pH following exercise. The first hour of post-exercise recovery in sea lampreys was associated with marked stimulation of JHnet (equivalent to base uptake), which approached -500 micromol kg-1 h-1. After 1 h, JHnet patterns had returned to resting rates. Analyses of net Na+ and Cl- movements (JNanet, JClnet) suggested that elevated net Cl- losses, which greatly exceeded net Na+ losses, accounted for most of the JHnet. Subsequent experiments, using radiotracers (22Na+, 36Cl-), indicated that differential increases in Cl- versus Na+ permeability accounted for the greater post-exercise Cl- losses and the corresponding stimulation of net proton excretion. Finally, metabolic acid budget analyses confirmed our hypothesis that rapid excretion of metabolic protons was the primary means used by sea lampreys to correct post-exercise extracellular acidosis. &lt;P&gt;

Wilms' tumor and gonadal dysgenesis in a child with the 2q37.1 deletion syndrome

Here we report Wilms' tumor, gonadal dysgenesis and a bifid uterus in an 18-month-old female with a terminal deletion of the long arm of chromosome 2 [46,XX,del(2)(q37.1)]. Since Wilms' tumor has been previously reported in the 2q37 deletion syndrome, the present observation raises the question of whether a tumor susceptibility gene maps to chromosome 2q37 and suggests giving consideration to the possible occurrence of Wilms' tumor in the course of disease.

Pleomorphic medium-sized T-cell lymphoma following Hodgkin's disease (nodular sclerosis type)

We describe a 32-year-old woman who presented with Hodgkin's disease, nodular sclerosis type II, subtype I, which necessitated several treatments over 11 years. The patient then developed pleomorphic, medium-sized T-cell lymphoma, which had a fatal outcome within 13 months. The role of radiotherapy, splenectomy, and chemotherapy in second tumor induction is compared with other sequential T-cell lymphomas. The significance of rare Epstein-Barr virus-infected cells during the T-cell lymphoma extension is discussed.

A new member of the ETS family fused to EWS in Ewing tumors

As a result of chromosome translocations, the EWS gene is fused to a variety of transcription factors in human solid neoplasia. In Ewing tumors EWS can be fused to four different members of the ETS family, namely FLI-1, ERG, ETV1 and E1AF. We have identified a new member of the ETS family, called FEV, which is fused to EWS in a subset of Ewing tumors. FEV encodes a 238 amino acid protein which contains an ETS DNA binding domain closely related to that of FLI-1 and ERG. However, the N-terminal portion of FEV is only 42 amino acids long which suggests that FEV is lacking important transcription regulatory domains contained in FLI-1 and ERG N-terminal parts. The C-terminal end of FEV is rich in alanine residues which may indicate that FEV is a transcription repressor. The FEV gene is encoded by three exons and is located on chromosome 2. FEV expression was only detected in adult prostate and small intestine but not in other adult nor in fetal tissues, thus indicating that FEV has a restricted expression pattern. Following a scheme similar to previously described translocations in Ewing tumors, a t(2;22) chromosome translocation fuses the N-terminal domain of EWS to the ETS DNA binding domain of FEV.

[Severe 5-fluorouracil toxicity in a woman treated for breast cancer with concurrent osteogenesis imperfecta and dehydrogenase deficiency]

Dihydropyrimidine dehydrogenase (DPD) is the principal enzyme involved in the catabolism of 5 fluorouracil (5 FU). The clinical importance of DPD has recently been demonstrated wit the identification of rare cases presenting a severe toxicity to 5 FU related to proven DPD deficiency. We report a new case in a patient with concurrent congenital osteogenesis imperfecta. We were surprised to find another similar association reported by Lyss. It is tempting to speculate that DPD activity may be abnormally regulated in osteogenesis imperfecta patients.

Integration of viral sequences into the c-myc gene in two mammary adenocarcinomas induced by polyomavirus in athymic nude mice

We report the analysis of polyomavirus (Py) DNA integration into chromosomal DNA of two Py-induced mammary adenocarcinomas of athymic nude mice. Prior observations had established that these tumors had high levels of episomal Py DNA, making analysis of integration sites difficult. Propagation of tumor cells in culture allows the isolation of lines which have lost episomal Py DNA but are still tumorigenic and thus can be used for in situ and Southern analysis of Py sequences. The data reported here support the conclusion that Py DNA integrated into and next to the c-myc gene, adding further importance to this tumor system which, in its modifications of c-myc expression, appears to be similar to some human mammary cancers. In situ hybridization experiments on metaphase chromosomes of tumor cells showed that (i) in both cases, there was a single integration site at the same position on the same chromosome in all cells of a given tumor, and (ii) integration sites were different in the two tumors; in one, it was located on chromosome 15, near the c-myc proto-oncogene, and in the other, it was situated in the distal part of chromosome 1. We have demonstrated a probable rearrangement between chromosome 1 and chromosome 15, in the region of Py insertion, thus suggesting that a specific site on chromosome 15 is involved in tumorigenesis. The discovery that Py DNA was integrated at specific sites in host chromosomes raised the questions of whether such integrations were correlated with the activation of specific oncogenes. The rearrangements of the c-myc proto-oncogene observed on Southern blot analysis for both tumors, along with similar integration patterns of Py sequences, the overexpression of the c-myc gene, and the synthesis of abnormal oversized hybrid transcripts between c-myc and Py genes, favor this hypothesis. Finally, the analysis of episomal Py DNA in various tumors shows viral populations presenting a specific deletion in a part of the Py late region. This deleted region in the episomal virus genome was systematically found integrated in chromosomal DNA, thus arguing for the importance of Py integration in the induction of mammary tumor.

A recurrent human papillomavirus integration site at chromosome region 12q14-q15 in SW756 and SK-v cell lines derived from genital tumors

The SW756 cell line, derived from an invasive cancer of the uterine cervix, harbours integrated human papillomavirus (HPV) 18 DNA sequences which have been located in chromosome band 12q13. By in situ hybridization experiments with tritiated and digoxigenin-labelled HPV18 probes on R-banded chromosomes, we now localize the integrated viral sequences in 12q14-q15. Interestingly, we have previously localized integrated HPV16 sequences in the same chromosomal region in SK-v cells, derived from a pre-invasive vulvar neoplasia. The chromosomal region 12q14-q15 could thus correspond to a preferential site for the integration of HPV DNA in genital tumors.