Targeting of IL-2 receptor with a caspase fusion protein disrupts autoimmunity in prediabetic and diabetic NOD mice.

AIMS/HYPOTHESIS: Interruption of IL-2 signalling is an attractive therapeutic target in autoimmune disorders. In this study we evaluated the effect of a fusion protein composed of IL-2 and caspase-3 (IL2-cas) on NOD mice, as compared with disease induction by cyclophosphamide. METHODS: IL2-cas was assessed in NOD mice at various ages and in conjunction with cyclophosphamide administration. The effect of IL2-cas on diabetogenic cells was evaluated in adoptive transfer experiments and in cell suspension in vitro. RESULTS: IL2-cas induced apoptosis in T cells expressing the alpha chain of the IL-2 receptor (cluster of differentiation [CD]25) in vitro, with superior survival of T cells expressing CD4 and forkhead box P3 (FOXP3). The fusion protein decreased mixed lymphocyte reactivity, and pretreatment with IL2-cas decreased the efficacy of adoptive transfer of diabetes into NOD severe combined immunodeficiency mice. Administration of one dose of IL2-cas decreased the incidence of diabetes in NOD mice, showing a superior beneficial effect when administered at young age, and effectively blocked induction of hyperglycaemia by cyclophosphamide, reducing the severity of islet inflammation. Administration of IL2-cas caused an acute increase in CD25(-)FOXP3(+) T cells in the lymph nodes, pancreas and thymus in NOD mice, with similar effects in wild-type mice. Administration of IL2-cas after onset of hyperglycaemia resulted in superior survival. CONCLUSIONS/INTERPRETATION: Targeted elimination of cells expressing the IL-2 receptor by this fusion protein disrupts the autoimmune pathogenesis in prediabetic and diabetic NOD mice, despite depletion of CD25(+) regulatory T cells. Furthermore, this particular fusion protein is permissive to the development of FOXP3(+) T cells that might contribute to protracted protection from the progression of insulitis and overt hyperglycaemia.

Phase I and pharmacokinetic study of halofuginone, an oral quinazolinone derivative in patients with advanced solid tumours.

PURPOSE: Halofuginone (tempostatin) is a synthetic derivative of a quinazolinone alkaloid showing anti-angiogenic, anti-metastatic and anti-proliferative effects in preclinical studies. The objectives of this phase I study were to assess the dose-limiting toxicities (DLTs), to determine the maximum tolerated dose (MTD) and to study the pharmacokinetics (PKs) of halofuginone when administered once or twice daily orally to patients with advanced solid tumours. METHODS: Patients were treated with escalating doses of halofuginone at doses ranging from 0.5 to 3.5 mg/day. For pharmacokinetic analysis plasma sampling was performed during the first and second course and assayed using a validated high-performance liquid chromatographic assay with mass spectrometric detection. RESULTS: Twenty-four patients received a total of 106 courses. The 'acute' MTD was reached at 3.5 mg/day, with nausea, vomiting, and fatigue as DLT. The recommended dose for chronic administration was defined as 0.5mg/day with the requirement of 5HT3 antagonists to control nausea and vomiting considered as DLT. Several patients experienced bleeding complications on treatment with halofuginone in which a causal relationship could not be excluded. The PKs of halofuginone were linear over the dose range studied with a large interpatient variability. CONCLUSIONS: In this study the DLT of halofuginone was nausea, vomiting, and fatigue. The recommended dose for phase II studies of halofuginone is 0.5mg administered orally, once daily.

Fluorouracil induces apoptosis and surface molecule modulation of peripheral blood leukocytes.

Little is known about the direct effect of chemotherapy on normal peripheral blood leukocytes (PBL) or its contribution to leukopenia. We examined 5'-fluorouracil's (5FU) effect on PBL apoptosis and adhesion molecules' expression in a single-drug solid-tumor model. Possible apoptosis mediators were examined. The study included 32 colorectal cancer patients; apoptosis was determined by annexin-V binding and light-scatter morphology before and after drug infusion. CD18, CD11a, CD11b, and CD63 membranal levels were assayed by flow cytometry. Apoptosis was increased post-5FU administration in neutrophils (PMN), monocytes and lymphocytes (P < 0.05). Levels of Fas receptor and activated caspase 3 did not vary indicating that the process was not mediated by caspase 3 in the timeframe studied. Reduced CD63 on monocytes and decreased CD18 expression on PMN and non-apoptotic monocytes were observed (P < or = 0.05). CD11a,b expression did not vary. Decreased CD18 and CD63 levels were demonstrated in apoptotic and non-apoptotic PBL implying a more direct association with the drug itself.

Ovarian cancer survival in Ashkenazi Jewish patients with BRCA1 and BRCA2 mutations.

PURPOSE: To compare the clinical characteristics and survival of Ashkenazi Jewish ovarian cancer patients with and without BRCA1 and BRCA2 mutations. METHODS: An unselected series of 118 Ashkenazi Jewish ovarian cancer patients were screened for the three common founder mutations in BRCA1 and BRCA2. Patient survival and other clinical characteristics of the tumours were compared in patients with BRCA1 or BRCA2 mutations and those without mutations. RESULTS: Twenty-seven individuals with invasive carcinomas were found to have mutations (14 with 185delAG and one with 5382insC in BRCA1 and 12 with 6174delT in BRCA2). No mutations were identified in the 20 patients with borderline tumours. For the invasive carcinomas, there was a survival advantage for BRCA1 and BRCA2 patients compared to patients without mutations, though the differences were not statistically significant. There were no significant differences in the histopathological characteristics of the tumours between the patient groups. CONCLUSION: These results are similar to those of other studies and suggest that ovarian cancer in BRCA1 and BRCA2 mutation carriers may have a distinct clinical behaviour.

Tamoxifen modulates apoptotic pathways in primary endometrial cell cultures.

Clinical data indicate that tamoxifen (TAM) therapy may cause an increased risk of endometrial pathology in postmenopausal but not in premenopausal women. Molecular mechanisms of the uterotrophic activity of TAM have not been clearly established nor its relevance to apoptosis in endometrial cells. The present study was implemented to evaluate the apoptotic effect of TAM on primary endometrial cell cultures in the presence or absence of steroid hormones (SHs). A total of 14 primary endometrial cell cultures were established and maintained both with and without SHs. Cell cultures were treated for 24 h with either 20 microM TAM or 10 nM estradiol. Apoptotic cells presented in a pre-G1 peak and the expression of bcl-2 were studied using flow cytometry. All endometrial cell cultures maintained in a SH-containing environment, except one, responded to TAM by a significant increase (P = 0.03) in the pre-G1 cell fraction, indicating a proapoptotic effect. A significant (P = 0.03) reduction in the pre-G1 peak equivalent to an antiapoptotic response was observed in 6 of 13 cell cultures maintained in a SH-deficient environment. In 4 of 10 cell cultures evaluated in both media, the pre-G1 population was medium dependent. In 8 of 10 cultures evaluated for Bcl2 levels, no trend was found in either media, but a dependency on SH content was observed. Comparison between effects of TAM and estradiol demonstrated identical trends, regardless of the menstrual phase or SH content in cell environments. These results suggest that TAM acts as an estrogen agonist on endometrial tissue in both environments. We conclude that TAM modulates apoptotic pathways in primary endometrial cell cultures. The SH content in the cell environment influences the apoptotic effect of TAM and determines the propensity for a cell to undergo apoptosis or, on the contrary, to resist apoptotic death in response to TAM treatment. This is in concordance with the observed clinical risk of endometrial pathologies in postmenopausal versus premenopausal women.

Incidence of BRCA1 and BRCA2 mutations in Ashkenazi colorectal cancer patients: preliminary study.

BACKGROUND: Mutations in BRCA genes are associated with an elevated incidence of colorectal cancer (CRC). While 20% of CRC patients have a familial history of colonic malignancies, in only 5% is the genetic setting understood. Thus, a majority of these patients lack any known genetic marker. Our aim was to explore the relevance of BRCA mutations to serve as such markers in the genetic screening and counseling of CRC patients. PATIENTS AND METHODS: 136 consecutive Israeli Jewish patients with sporadic CRC were screened for BRCA "Ashkenazi mutations": 185delAG, 5382insC and 6174delT. Carrier status was evaluated employing PCR, restriction analysis, SSCP and a Pronto BRCA kit. RESULTS: We found one 185delAG and two 6174delT carriers, altogether three Ashkenazi carriers out of 87 Ashkenazi patients tested, 3.5%. No carriers were found among the Arabs and non-Ashkenazi Jews surveyed. CONCLUSIONS: Our preliminary results show elevated rates of BRCA "Ashkenazi mutations" in Ashkenazi CRC patients, suggesting their involvement in CRC carcinogenesis. An implementation of a wider study will establish the role of these mutations as genetic markers for CRC.

Adenomatous polyposis coli I1307K mutation in Jewish patients with different ethnicity: prevalence and phenotype.

BACKGROUND: A new mutation, I1307K, recently was reported in the adenomatous polyposis coli (APC) gene. This mutation was found to be predominant in Ashkenazi Jews, creating a hypermutable area and predisposing the development of carcinoma. The objective of the current study was to estimate the prevalence of this mutation in several of the ethnic groups that comprise the Israeli population and to elucidate the clinical features of the mutation carriers with colorectal carcinoma (CRC). METHODS: A total of 111 consecutive CRC patients were evaluated and their medical history and clinical data recorded. The general population (298 Ashkenazim and 189 Yemenites) also was tested for the presence of this mutation. Mutation screening was performed using both the polymerase chain reaction-based amplification refractory mutation system and a commercial APC kit. RESULTS: Of the total of 111 CRC patients, 15 (13.5%) carried the I1307K mutation and 26 of 487 subjects from the general population (5.3%) carried the I1307K mutation (P = 0.004). Among the 71 Ashkenazi CRC patients there were 12 carriers (16.9%) whereas 17 of the 298 Ashkenazi Jewish general population (5.7%) carried the mutation (P = 0.004). Of the 4 CRC patients of Yemenite origin, 3 carried the mutation and 9 carriers were found among 189 subjects in the general Yemenite population (4.7%) (P = 0.0007). None of the 34 Sepharadic or 2 Arab CRC patients carried the APC I1307K allele. Late age at diagnosis (64.6 years +/- 10.0, which is similar to that of the noncarriers), mostly right-sided tumors, and moderate to good differentiation constituted the phenotype of the mutation carriers. CONCLUSIONS: The authors believe the findings of the current study broaden the known spectrum of ethnic groups in which the APC I1307K mutation is prevalent. The phenotype of the mutation carrier CRC patients does not conform to the expected familial pattern of germline mutations. The phenotype and the differential incidence rate of CRC among APC I1307K carriers of various ethnic groups suggest low penetrance.

Interleukin 2-Bax: a novel prototype of human chimeric proteins for targeted therapy.

During the past few years many chimeric proteins have been developed to target and kill cells expressing specific surface molecules. Generally, these molecules carry a bacterial or plant toxin that destroys the unwanted cells. The major obstacle in the clinical application of such chimeras is their immunogenicity and non-specific toxicity. We have developed a new generation of chimeric proteins, taking advantage of apoptosis-inducing proteins, such as the human Bax protein, as novel killing components. The first prototype chimeric protein, IL2-Bax, directed toward IL2R-expressing cells, was constructed, expressed in Escherichia coli and partially purified. IL2-Bax increased the population of apoptotic cells in a variety of target T cell lines, as well as in human fresh PHA-activated lymphocytes, in a dose-dependent manner and had no effect on cells lacking IL2R expression. The IL2-Bax chimera represents an innovative approach for constructing chimeric proteins comprising a molecule that binds a specific cell type and an apoptosis-inducing protein. Such new chimeric proteins could be used for targeted treatment of human diseases.

Linker-based GnRH-PE chimeric proteins inhibit cancer growth in nude mice.

Since the number of cancer-related deaths has not decreased in recent years, major efforts are being made to find new drugs for cancer treatment. In this report we introduce the gonadotropin releasing hormone-Pseudomonas exotoxin (GnRH-PE) based chimeric proteins L-GnRH-PE66 and L-GnRH-PE40. These proteins are composed of a GnRH moiety attached to modified forms of Pseudomonas exotoxin via a polylinker (gly4ser)2. The chimeric proteins L-GnRH-PE66 and L-GnRH-PE40 have the ability to target and kill adenocarcinoma cell lines in vitro, whereas non-adenocarcinoma cell lines are not affected. We demonstrate that L-GnRH-PE66 and L-GnRH-PE40 efficiently inhibit cancer growth. Nude mice were injected subcutaneously with the SW-48 adenocarcinoma cell line to produce xenograft tumours. When the tumours were established and visible, the animals were injected with chimeric proteins for 10 days. At the end of this period, a reduction of up to 3-fold in tumor size was obtained in the treated mice, as compared with the control group, which received equivalent amounts of GnRH; the difference was even greater 13 days after termination of treatment. Thus, the chimeric proteins L-GnRH-PE66 and L-GnRH-PE40 are promising candidates for treatment of a variety of adenocarcinomas and their use in humans should be considered.

Adenocarcinoma cells are targeted by the new GnRH-PE66 chimeric toxin through specific gonadotropin-releasing hormone binding sites.

Luteinizing hormone-releasing hormone, also termed gonadotropin-releasing hormone (GnRH), accounts for the hypothalamic-pituitary gonadal control of human reproduction. The involvement of GnRH has been demonstrated in several carcinomas of hormone-responsive tissues. Exploiting this common feature, we constructed a Pseudomonas exotoxin (PE)-based chimeric toxin (GnRH-PE66) aimed at targeting those cancer cells bearing GnRH binding sites. We report here the strong growth inhibition and killing of a surprisingly wide variety of cancers, confined to the adenocarcinoma type. These cancer cells arising from hormone-responsive tissues, as well as non-responsive ones, express specific GnRH binding sites as indicated by the marked killing of ovarian, breast, endometrial, cervical, colon, lung, hepatic, and renal adenocarcinoma. This cytotoxicity is specific as it could be blocked upon addition of excess GnRH. The specificity of GnRH-PE66 chimeric toxin was also confirmed by GnRH binding assays, and its ability to prevent the formation of colon cancer xenografts in nude mice is presented. Although the functional role of specific GnRH binding sites in human carcinomas remains obscure, GnRH-PE66 displays considerable targeting potential and its use as a therapeutic agent for cancer should be considered.

B-cell non-Hodgkin's lymphoma: evidence for the t (14;18) translocation in all hematopoietic cell lineages.

BACKGROUND: B cells of patients with non-Hodgkin's lymphoma (B-NHL) harbor specific chromosomal translocations, including t(14;18), the most common aberration found in this disease. The translocation involves the immunoglobulin (Ig) heavy-chain joining (JH) region gene on chromosome 14 and the BCL2 gene on chromosome 18, resulting in dysregulated expression of the BCL2 gene. The t(14;18) translocation has been thought to occur in the pre-B-cell stage, during the first event of Ig gene rearrangement. PURPOSE: This study was conducted to investigate the potential involvement of nonlymphoid lineages in B-NHL. METHODS: We studied the t(14;18) translocation and other frequently occurring translocations in total bone marrow aspirates of 10 patients with B-NHL, with the use of the fluorescence in situ hybridization (FISH) technique. We also performed cytogenetic analyses on representative bone marrow aspirates from the patients. Moreover, to define which of the major cell lineages present in the bone marrow carry the t(14;18) translocation, we used a series of monoclonal antibodies together with fluorescence-activated cell sorter (FACS) analyses to purify cells positive for CD3 (T cells), CD19 (B cells), CD10 (CALLA-positive cells), CD41a (megakaryocytic cells), CD13 (myeloid cells), and glycophorin A (erythroid cells). The cells of each subgroup underwent FISH analysis with the use of JH and BCL2 probes to detect the t(14;18) translocation. Bone marrow samples obtained from five healthy donors served as controls. RESULTS: Bone marrow cells from eight of the 10 patients studied carried the t(14;18) translocation. When present, the translocation was observed in many or even all of the cell lineages (lymphoid, myeloid, megakaryocytic, and erythroid) present in the bone marrow, including peripheral blood progenitor stem cells; for seven of the eight patients carrying the translocation, it was found in 96%-100% of the unfractionated bone marrow cells as well as in all of the FACS-purified cell fractions in which it could be detected or studied. Conventional cytogenetic analyses performed on representative bone marrow aspirates confirmed the results obtained by FISH analysis. Cells in control bone marrow samples obtained from the five healthy donors were negative for the t(14;18) translocation by FISH analysis. CONCLUSIONS: Our findings indicate that the t(14;18) translocation most probably occurs in a very early multilineage progenitor stem cell. IMPLICATIONS: Given that the t(14;18) chromosomal translocation was found in all types of bone marrow cells when only the B cells were malignant, our results suggest that this translocation is not sufficient to induce neoplastic transformation. This finding underscores the need for the development of new approaches for the detection and surveillance of B-NHL.

The BCL-1, BCL-2, and BCL-3 oncogenes are involved in chronic lymphocytic leukemia. Detection by fluorescence in situ hybridization.

The putative oncogenes BCL-1, BCL-2, and BCL-3 are commonly rearranged by translocations to the immunoglobulin genes in B-cell malignancies. However, Southern blotting rarely detected their involvement in chronic lymphocytic leukemia (CLL). This discrepancy could stem from some unique features of the oncogenesis of CLL or be due to shortcomings of Southern blotting. We have therefore evaluated the role of fluorescence in situ hybridization (FISH) in the detection of these oncogenes in CLL. Twenty consecutive CLL patients were studied by FISH for the detection of BCL-1, BCL-2, or BCL-3 rearrangement and for the presence of trisomy 12. Selected patients were also evaluated by classical cytogenetic techniques and by Southern blot analysis. Juxtaposition of JH and BCL-1 was demonstrated in 10 (50%), BCL-2 in three (15%), and BCL-3 in four (20%) of the patients. Trisomy 12 was detected by FISH in 11 (55%) patients. The coexistence of trisomy 12 and translocation of the BCL-1 oncogene was common. Three of the patients had chromosomal aberrations compatible with those detected by FISH. In contrast, in none of the five patients selected by their positive FISH findings was a rearrangement demonstrated by Southern blotting. We conclude that FISH is a sensitive method for the detection of oncogene involvement in CLL. Mainly BCL-1, but also BCL-2 and BCL-3, are commonly translocated to the immunoglobulin heavy chain locus on chromosome 14. These translocations are often associated with trisomy 12. These findings indicate that the BCL oncogenes are commonly involved in CLL and lend support to the multi-hit theory of cancer development.

Potent antileukemic activity of the novel agents norsegoline and dibezine.

We examined the effect of norsegoline, a natural marine product, and dibezine, a synthetic product, on the survival of human myeloid progenitor cells [colony-forming unit-cells (CFU-C)] from normal individuals and from 10 patients with Philadelphia-positive chronic myelogenous leukemia (CML) in chronic phase and blastic crisis. We compared their effect to the effect of IFN-alpha. Norsegoline, dibezine, and IFN-alpha inhibited the proliferation of CFU-C in a dose-dependent manner. The number of CFU-C from bone marrow (BM) of five CML patients in chronic phase exposed for 16 h to norsegoline (10(-8)-10(-6)M), dibezine (10(-8)-10(-6)M), and IFN-alpha (500 units/ml) was found to be statistically lower (P < 0.05) than the number of CFU-C derived from normal individuals. A 16-h drug exposure of CD34(+) cells isolated from the peripheral blood of three CML patients in blastic crisis and from BM of two patients in chronic phase resulted in a marked inhibition in the ability of the cells to proliferate in liquid culture and a reduction in CFU-C content. Using the fluorescent in situ hybridization technique, we evaluated detection of the BCR/ABL fusion product in the CD34(+) cells. All five patients were 100% Philadelphia positive at diagnosis. BCR/ABL translocations were detected in 94.6 +/- 0.6% of cells following their growth in liquid culture for 7 days. Following exposure of CD34(+) cells to norsegoline, dibezine, or IFN-alpha, BCR/ABL fusion signals could be detected in 73 +/- 11%, 66.5 +/- 4. 7%, and 66.0 +/- 2.5% of cells from BM and 72.3 +/- 5%, 68.8 +/- 7%, and 60.6 +/- 6.8% of peripheral blood, respectively. Our data indicate that norsegoline and dibezine have in vitro an antileukemic effect against Philadelphia-positive cells and may be used in conjunction with currently available agents for ex vivo purging of BM and/or peripheral blood of CML patients in conjunction with autologous bone marrow transplantation.

ABL and BCR genes are not imprinted in androgenetic and gynogenetic human tissues.

In the translocation leading to the formation of the Philadelphia chromosome, the hallmark of chronic myeloid leukemia (CML), the translocated chromosome 9 (ABL), is of paternal descent whereas chromosome 22 (BCR) is of maternal origin (1). To study possible imprinting of the human ABL and BCR genes, we used human tissues exclusively endowed with their maternally (benign teratoma) or paternally (complete hydatidiform mole) inherited chromosomes. Using the sensitive PCR technique followed by northern blotting, we demonstrate here that ABL and BCR are expressed to a similar extent in androgenetic and gynogenetic human tissues, thus suggesting that ABL and BCR genes are not imprinted in these human tissues.

Mechanisms of dichotomous action of IL-2-Pseudomonas exotoxin 40 (IL-2-PE40) on cell-mediated and humoral immune response.

IL-2-PE40 is a chimeric protein composed of human IL-2 genetically fused to the amino terminus of a modified form of Pseudomonas exotoxin lacking its cell recognition domain. The immunosuppressive efficacy of IL-2-PE40 was demonstrated in several experimental murine transplant and autoimmune models. However, some observations suggested that IL-2-PE40 could not inhibit the humoral response. In this report, we describe the dichotomous effects of IL-2-PE40 on humoral and cell-mediated immune response in a simple, well characterized in vivo model. Although IL-2-PE40 inhibited the cell-mediated delayed type hypersensitivity reaction to SRBC, it increased the humoral immune response to the same Ag. To understand the mechanism of dichotomous action of IL-2-PE40 on the immune response, IL-2R-bearing T cells were treated with IL-2-PE40 in vitro and the cytokine expression was studied at mRNA and protein level. Similar to IL-2, IL-2-PE40 promoted the expression of T helper 1-like (IFN-gamma) as well as T helper 2-like (IL-4, IL-10) cytokines. These in vitro studies show that IL-2-PE40 can induce signal transduction in activated T cells through the IL-2R before exerting its cytotoxic effect. In contrast to DTH reaction, humoral immune response requires T cell help only for a limited period. Therefore, the short-term stimulation of T helper cells by IL-2-PE40 may be sufficient in vivo to mediate a B cell response in the local environment, whereas the DTH reaction and other cell-mediated immune responses are inhibited by the toxin moiety of the chimeric protein.

Detection of minimal residual disease state in chronic myelogenous leukemia patients using fluorescence in situ hybridization.

Detection of minimal residual disease and relapse remain major problems in chronic myelogenous leukemia (CML) patients following bone marrow transplantation (BMT). In order to disclose the 9;22 Philadelphia translocation, we used a fluorescence in situ hybridization (FISH) technique. BCR and ABL gene fragments were used as probes for the detection of the BCR/ABL fusion product in peripheral blood and bone marrow cells from 11 CML patients in which 5 were post-BMT. The sensitivity and specificity of this approach were compared to conventional cytogenetic and polymerase chain reaction (PCR) methods. FISH demonstrated a high degree of sensitivity (1%) for the detection of the BCR/ABL translocation in these patients. A linear correlation was found between FISH detection of the BCR/ABL fusion product and routine chromosomal analysis (r = 0.995; p < 0.001). Detection of the BCR/ABL signal by FISH was observed in all patients showing a positive PCR signal. A significant reduction in BCR/ABL signal was observed post-transplant (p < 0.001). However, the BCR/ABL translocation was detected in four of five transplanted patients immediately (0.75-2.5 months) following transplant and was found in patients with a low expression of the translocation.

Detection of minimal residual disease after sex-mismatch bone marrow transplantation in chronic myelogenous leukemia by fluorescence in situ hybridization.

Detection of minimal residual disease is one of the major goals in bone marrow transplantation. We used a fluorescence in-situ hybridization technique to detect residual Philadelphia-chromosome positive cells in chronic myelogenous leukemia (CML) patients after sex-mismatch BMT. We analyzed the level of detection using probes for the BCR/ABL fusion product by comparison with results obtained with probes for the Y and X sex chromosomes. Detection of sex-mismatch chromosomes was significantly higher than that of the BCR/ABL translocation. In contrast, a higher specificity of residual tumor cell detection by the BCR/ABL probe was demonstrated because most of the sex-mismatch cells detected by FISH had a normal karyotype. Tumor-specific markers probes are thus superior and more accurate than sex-mismatch probes for detection of MRD in CML patients after BMT.

Detection of bcl rearrangements in B-CLL by fluorescence in situ hybridization.

Data concerning oncogene activation in CLL are very limited. When studied by Southern blot, rearrangements of bcl-1, bcl-2, and bcl-3 have been only infrequently reported. We evaluated the role of fluorescence in situ hybridization (FISH) in the detection of gene rearrangements in two CLL patients. We used multiple DNA probes, including those of chromosome 12, immunoglobulin heavy and light chains, and the oncogenes bcl-1, bcl-2, and bcl-3. Additionally, routine cytogenetic study was performed. In one patient, trisomy 12 and bcl-2 translocation were demonstrated by both methods, while trisomy 12 and bcl-1 translocation were seen in the second patient, who had a normal karyotype. Larger studies should evaluate the role of FISH in the detection of oncogene involvement in CLL and compare it with other molecular methods.