RESUMO
BACKGROUND: Hormone receptor expression is a known positive prognostic and predictive factor in breast cancer; however, limited evidence exists on its prognostic impact on prognosis of young patients harboring a pathogenic variant (PV) in the BRCA1 and/or BRCA2 genes. PATIENTS AND METHODS: This international, multicenter, retrospective cohort study included young patients (aged ≤40 years) diagnosed with invasive breast cancer and harboring germline PVs in BRCA genes. We investigated the impact of hormone receptor status on clinical behavior and outcomes of breast cancer. Outcomes of interest [disease-free survival (DFS), breast cancer-specific survival (BCSS), and overall survival (OS)] were first investigated according to hormone receptor expression (positive versus negative), and then according to breast cancer subtype [luminal A-like versus luminal B-like versus triple-negative versus human epidermal growth factor receptor 2 (HER2)-positive breast cancer]. RESULTS: From 78 centers worldwide, 4709 BRCA carriers were included, of whom 2143 (45.5%) had hormone receptor-positive and 2566 (54.5%) hormone receptor-negative breast cancer. Median follow-up was 7.9 years. The rate of distant recurrences was higher in patients with hormone receptor-positive disease (13.1% versus 9.6%, P < 0.001), while the rate of second primary breast cancer was lower (9.1% versus 14.7%, P < 0.001) compared to patients with hormone receptor-negative disease. The 8-year DFS was 65.8% and 63.4% in patients with hormone receptor-positive and negative disease, respectively. The hazard ratio of hormone receptor-positive versus negative disease changed over time for DFS, BCSS, and OS (P < 0.05 for interaction of hormone receptor status and survival time). Patients with luminal A-like breast cancer had the worst long-term prognosis in terms of DFS compared to all the other subgroups (8-year DFS: 60.8% in luminal A-like versus 63.5% in triple-negative versus 65.5% in HER2-positive and 69.7% in luminal B-like subtype). CONCLUSIONS: In young BRCA carriers, differences in recurrence pattern and second primary breast cancer among hormone receptor-positive versus negative disease warrant consideration in counseling patients on treatment, follow-up, and risk-reducing surgery.
Assuntos
Proteína BRCA1 , Proteína BRCA2 , Neoplasias da Mama , Receptor ErbB-2 , Receptores de Estrogênio , Receptores de Progesterona , Humanos , Feminino , Adulto , Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Neoplasias da Mama/mortalidade , Neoplasias da Mama/metabolismo , Estudos Retrospectivos , Proteína BRCA1/genética , Proteína BRCA2/genética , Receptor ErbB-2/metabolismo , Receptor ErbB-2/genética , Receptores de Estrogênio/metabolismo , Receptores de Progesterona/metabolismo , Prognóstico , Intervalo Livre de Doença , Adulto Jovem , Mutação em Linhagem Germinativa , Heterozigoto , Biomarcadores Tumorais/genética , Biomarcadores Tumorais/metabolismoRESUMO
BACKGROUND: Knowledge is growing on the safety of assisted reproductive techniques (ART) in cancer survivors. No data exist, however, for the specific population of breast cancer patients harboring germline BRCA1/2 pathogenic variants. PATIENTS AND METHODS: This is a multicenter retrospective cohort study across 30 centers worldwide including women diagnosed at ≤40 years with stage I-III breast cancer, between January 2000 and December 2012, harboring known germline BRCA1/2 pathogenic variants. Patients included in this analysis had a post-treatment pregnancy either achieved through use of ART (ART group) or naturally (non-ART group). ART procedures included ovulation induction, ovarian stimulation for in vitro fertilization or intracytoplasmic sperm injection, and embryo transfer under hormonal replacement therapy. RESULTS: Among the 1424 patients registered in the study, 168 were eligible for inclusion in the present analysis, of whom 22 were in the ART group and 146 in the non-ART group. Survivors in the ART group conceived at an older age compared with those in the non-ART group (median age: 39.7 versus 35.4 years, respectively). Women in the ART group experienced more delivery complications compared with those in the non-ART group (22.1% versus 4.1%, respectively). No other apparent differences in obstetrical outcomes were observed between cohorts. The median follow-up from pregnancy was 3.4 years (range: 0.8-8.6 years) in the ART group and 5.0 years (range: 0.8-17.6 years) in the non-ART group. Two patients (9.1%) in the ART group experienced a disease-free survival event (specifically, a locoregional recurrence) compared with 40 patients (27.4%) in the non-ART group. In the ART group, no patients deceased compared with 10 patients (6.9%) in the non-ART group. CONCLUSION: This study provides encouraging safety data on the use of ART in breast cancer survivors harboring germline pathogenic variants in BRCA1/2, when natural conception fails or when they opt for ART in order to carry out preimplantation genetic testing.
Assuntos
Neoplasias da Mama , Adulto , Proteína BRCA1/genética , Neoplasias da Mama/genética , Feminino , Células Germinativas , Humanos , Recidiva Local de Neoplasia/etiologia , Gravidez , Técnicas de Reprodução Assistida/efeitos adversos , Estudos RetrospectivosRESUMO
A new human retrovirus was isolated from a continuous cell line derived from a patient with CD4+ Tac- cutaneous T cell lymphoma/leukemia. This virus is related to but distinct from human T cell leukemia/lymphoma virus types I and II (HTLV-I and HTLV-II) and human immunodeficiency virus (HIV-1). With the use of a fragment of provirus cloned from one patient with T cell leukemia, closely related sequences were found in DNA of the cell line and of tumor cells from seven other patients with the same disease; these sequences were only distantly related to HTLV-I. The phenotype of the cells and the clinical course of the disease were clearly distinguishable from leukemia associated with HTLV-I. All patients and the wife of one patient showed a weak serological cross-reactivity with both HTLV-I and HIV-1 antigens. None of the patients proved to be at any apparent risk for HIV-1 infection. The name proposed for this virus is HTLV-V, and the date indicate that it may be a primary etiological factor in the major group of cutaneous T cell lymphomas/leukemias, including the sporadic lymphomas known as mycoses fungoides.
Assuntos
Deltaretrovirus/isolamento & purificação , Leucemia/microbiologia , Linfoma/microbiologia , Antígenos Virais/análise , Deltaretrovirus/classificação , Deltaretrovirus/ultraestrutura , Feminino , Humanos , Masculino , Microscopia Eletrônica , Linfócitos T/citologiaRESUMO
We studied the presence of microsatellite instability (MSI) in a series of 108 gastric cancers (GCs) previously identified in an epidemiological study carried out in a high-risk area around Florence. To investigate associations between MSI and GC family history, 34 cases (31.5%) who had a GC-affected first-degree relative were included in the series. A family history positive for colorectal cancer was reported quite rarely (5.6%). The analysis of 6 microsatellite loci in DNA from paired normal tissue and tumor samples microdissected from paraffin-embedded specimens revealed varying degrees of instability: 56 cases (51.8%) did not show instability at any of the 6 loci; 19 (17.6%) showed instability at 1 locus; 16 (14.8%) showed instability at 2 loci; 11 (10.2%) showed instability at 3 loci; 4 (3.7%) showed instability at 4 loci; and 2 (1.9%) showed instability at 5 loci. The replication error-positive (RER+) phenotype, defined as the presence of MSI at 2 or more loci, had a frequency of 30.6% (33 of 108) and tended to be positively associated with female sex, intestinal histological type, advanced tumor stage, vascular invasion, positive GC family history, and blood group of A type. No correlation emerged between age at diagnosis and RER+ phenotype, whereas a significant association with the RER+ phenotype was shown by the antral location. A multivariate analysis adjusting for a selected group of potential confounding factors confirmed the strong association of the RER+ phenotype with the antral location (P = 0.001) and with a positive GC family history (P < 0.05). Survival analyses at 5 and 8 years showed no difference between RER+ and RER- patients, even when corrected for stage distribution. By the microdissection technique, we also used microsatellite allele patterns to investigate intratumoral heterogeneity and genetic relationships between tumors and adjacent dysplasia and/or intestinal metaplasia. Areas of metaplasia and dysplasia demonstrated MSI only in cases with MSI-positive tumors. In MSI-positive tumors, there was consistent evidence of intratumoral microsatellite allele heterogeneity, indicating the presence of genetically divergent tumor cell clones within the same neoplasm.
Assuntos
Repetições de Microssatélites , Neoplasias Gástricas/genética , Neoplasias Gástricas/patologia , Fatores Etários , Idoso , Neoplasias Colorretais/genética , DNA/química , DNA de Neoplasias/química , Família , Feminino , Marcadores Genéticos , Humanos , Itália/epidemiologia , Masculino , Pessoa de Meia-Idade , Invasividade Neoplásica , Estadiamento de Neoplasias , Valores de Referência , Fatores de Risco , Neoplasias Gástricas/epidemiologia , Neoplasias Gástricas/mortalidade , Análise de SobrevidaRESUMO
Chronic obstructive pulmonary disease (COPD) and asthma are lung inflammatory diseases that represent major public health problems. The primary, and often unique, method to evaluate lung function is spirometry, which reflects disease severity rather than disease activity. Moreover, its measurements strictly depend on patient's compliance, physician's expertise and data interpretation. The limitations of clinical history and pulmonary function tests have encouraged focusing on new possible tracers of diseases. The increase of the inflammatory response in the lungs represents an early pathological event, so biological markers related to inflammation may play key roles in earlier diagnosis, evaluation of functional impairment and prognosis. Biomarkers are measurable indicators associated with the presence and/or severity of a biological or pathogenic process, which may predict functional impairment, prognosis and response to therapy. The traditional approach based on invasive techniques (bronchoalveolar lavage and biopsies) may be replaced, at least in part, by using less invasive methods to collect specimens (sputum and blood), in which biomarkers could be measured. Proteomics, by the association between different protein profiles and pathogenic processes, is gaining an important role in pulmonary medicine allowing a more precise discrimination between patients with different outcomes and response to therapy. The aim of this review was to evaluate the use of biomarkers of airway inflammation in the context of both research and clinical practice.
Assuntos
Asma/metabolismo , Mediadores da Inflamação/metabolismo , Doença Pulmonar Obstrutiva Crônica/metabolismo , Escarro/metabolismo , Animais , Asma/sangue , Asma/diagnóstico , Biomarcadores/sangue , Biomarcadores/metabolismo , Biópsia , Lavagem Broncoalveolar , Humanos , Mediadores da Inflamação/sangue , Prognóstico , Doença Pulmonar Obstrutiva Crônica/sangue , Doença Pulmonar Obstrutiva Crônica/diagnóstico , Testes de Função Respiratória/métodos , Espirometria/métodosRESUMO
We analyzed 81 cases of primary breast carcinoma and 7 cases of fibroadenoma for microsatellite instability at eight loci. Twenty-seven cases (33.3%) manifested aberrant microsatellite alleles: 7 (8.6%) at one locus and 20 (24.7%) at two or more loci [tumors with replication error-positive (RER+) phenotype]. No evidence of microsatellite instability was observed in fibroadenomas. We investigated correlations between RER+ phenotype and clinicopathological characteristics of the carcinomas. The RER+ phenotype was statistically associated with large tumor diameter; of 19 RER+ tumors with measured size, 16 were > 2 cm, compared to 28 of 58 tumors with no evidence of microsatellite instability or with shifts in allele sizes limited to one locus (P = 0.005, chi2 test). Consistently, there was also a strong statistical association between RER+ phenotype and lymph node metastasis; 14 of 19 RER+ tumors with known lymph node status were N+, compared to 15 of 59 tumors with no evidence of microsatellite instability or with allele shifts limited to one locus (P = 0.0002, chi2 test). Correlations with age of patients, proliferative activity, histotype (ductal versus lobular), and grade of differentiation were not statistically significant, although the RER+ phenotype was more frequent in lobular and high-grade ductal carcinomas, in carcinomas with high proliferative activity, and in carcinomas from patients =50 years. Data concerning cancer(s) in first and/or second degree relatives were available for 66 cases, including 33 positive and 33 negative for family history of cancer. No correlations were detected between RER+ phenotype and family history of cancer. In conclusion, our results indicate that in breast cancer, microsatellite instability is associated with clinicopathological parameters that are considered predictors of recurrent disease and aggressive behavior.
Assuntos
Neoplasias da Mama/genética , Repetições de Microssatélites/genética , Adulto , Idoso , Neoplasias da Mama/fisiopatologia , Feminino , Marcadores Genéticos/genética , Humanos , Metástase Linfática , Pessoa de Meia-IdadeRESUMO
We analysed the immunohistochemical expression pattern of the distinct carbohydrate epitopes of the TAG-72 molecule, defined by the monoclonal antibodies (MAbs) B72.3, CC-49 and CC-83, in 92 breast carcinomas of different histological type, and in other histological components identified in the mammary tissue samples studied. The results were correlated with the clinico-pathological characteristics of the tumours, and with their proliferative activity, assessed by thymidine labelling index (TLI). Expression of the TAG-72 epitopes was detected in all the tumour histotypes analysed, but patterns of immunoreactivity tended to vary in relation to type and level of differentiation. The comparative analysis of the reactivities of the three anti-TAG-72 MAbs revealed differences in their ability to recognise neoplastic lesions. MAb CC-49 reacted with the highest percentage of tumours (82%), and also tended to yield the highest percentages of immunoreactive cancer cells, while B72.3 and CC-83 reacted with lower percentages of tumours (respectively, 55 and 51%), and identified lower percentages of immunoreactive cells. High levels of expression of the three TAG-72 epitopes were detected in areas of in situ ductal carcinoma. Comparatively lower levels of immunohistochemical positivity were found in atypical epithelial hyperplasia, normal mammary epithelium and epithelium with cystic disease. TAG-72 epitope expression was correlated with prognostic parameters. The synchronous expression of the three epitopes significantly correlated with large tumour size (> 2 cm), and with high histological grade. No correlations could be demonstrated between TAG-72 phenotypes and nuclear grade, lymph node status and proliferative activity (high versus low).
Assuntos
Antígenos de Neoplasias/análise , Biomarcadores Tumorais/análise , Neoplasias da Mama/imunologia , Carcinoma Ductal de Mama/imunologia , Carcinoma Lobular/imunologia , Epitopos/análise , Glicoproteínas/análise , Anticorpos Monoclonais , Antígenos de Neoplasias/imunologia , Feminino , Glicoproteínas/imunologia , Humanos , Técnicas ImunoenzimáticasRESUMO
Lymphadenopathy with no apparent cause had been reported in a group of women participating in a mammary tumor prevention program. A screening for retrovirus infection was organized to detect the virus as possible etiological agents. Data show a high percentage of positivity for HIV-1 among these lymphadenopathy patients, and surprisingly for HTLV-I, while no such positivity for either virus was found in matched controls or in patients where a different causal agent for lymphadenopathy was found. Of 26 seropositives, 23 deny any risk factor for HIV-1 and do not come from a HTLV-I known endemic area, but while it is impossible to exclude their knowledge of risk factors, it is worth noting that none of them presented a HTLV-I/HIV-1 double infection, which is very frequent in intravenous drug abusers, the major risk group in Italy. On the basis of these data spread of HTLV-I and HIV-1 appears to be more important in Italy than previously thought, and not confined to well-defined groups or, at least, among those who believe they do not belong to a risk group and therefore can represent a major vehicle for virus diffusion. Institution of screening for HTLV-I in blood donors should be taken immediately, and retrovirus infection risk criteria must be revised.
Assuntos
Neoplasias da Mama/prevenção & controle , Infecções por HIV/diagnóstico , HIV-1/isolamento & purificação , Infecções por HTLV-I/diagnóstico , Vírus Linfotrópico T Tipo 1 Humano/isolamento & purificação , Doenças Linfáticas/microbiologia , Adulto , Idoso , Animais , Feminino , Humanos , Pessoa de Meia-Idade , Ratos , Fatores de RiscoRESUMO
DNA ploidy and thymidine-labeling index (TLI) have been introduced as prognostic indicators to characterize the biological behavior of breast cancer for the selection of patients eligible for adjuvant therapy. The aim of this study was to evaluate the prognostic significance and correlation between ploidy status, TLI and other common histopathologic parameters such as histotype, stage, grading, lymph node metastasis, hormone receptors and recurrence. DNA ploidy and TLI were assessed for 68 breast cancer patients, 27 to 85 years of age. DNA histograms, analyzed with static cytometry, were: diploid in 21(31%) and non diploid in 47 (70%). High TLI values were observed in 16 cases (24%), medium values in 46 cases (68%) and low values in 6 cases (8.5%). DNA ploidy and TLI showed a statistically significant correlation, as independent parameters, with recurrence (respectively, p = 0.0267 and p < 0.0001). Therefore, DNA ploidy and TLI may be considered additional prognostic parameters to be utilized besides all the other clinical-pathologic data for the assessment of these lesions, and to plan therapeutic strategies.
Assuntos
Neoplasias da Mama/genética , DNA de Neoplasias/análise , Ploidias , Timidina/metabolismo , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias da Mama/mortalidade , DNA de Neoplasias/biossíntese , Feminino , Humanos , Pessoa de Meia-Idade , Estadiamento de Neoplasias , PrognósticoRESUMO
Chemotherapy is the most effective treatment for inoperable patients (70%) affected with non-small cell lung cancer (NSCLC). The early detection of tumour progression is mandative in order to promptly shift these patients towards salvage or supportive therapy. The present authors investigated the clinical value of a panel of tumour markers, elaborated by means of discriminant analysis, as a follow-up indicator for the detection of tumour progression. The serum levels of tissue polypeptide antigen (TPA), CYFRA-21.1, neuron-specific enolase (NSE) and carcino-embryonic antigen (CEA) were determined before chemotherapy and after three cycles of treatment. Discriminant analysis generated a formula (canonic variable) which correctly classified the 87.8% of the 74 subjects (86.1% of the 36 progressive diseases and 89.5% of 38 non-progressive diseases). This approach produces an algorithm able to calculate a progression score in NSCLC patients which can be helpful for following-up care and therapy control of these patients.
Assuntos
Biomarcadores Tumorais/sangue , Antígeno Carcinoembrionário/sangue , Carcinoma Pulmonar de Células não Pequenas/sangue , Carcinoma Pulmonar de Células não Pequenas/tratamento farmacológico , Neoplasias Pulmonares/sangue , Neoplasias Pulmonares/tratamento farmacológico , Fosfopiruvato Hidratase/sangue , Antígeno Polipeptídico Tecidual/sangue , Adulto , Idoso , Idoso de 80 Anos ou mais , Algoritmos , Análise Discriminante , Progressão da Doença , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Resultado do TratamentoAssuntos
Síndrome da Imunodeficiência Adquirida/epidemiologia , Infecções por Deltaretrovirus/epidemiologia , Soropositividade para HIV/epidemiologia , Anticorpos Antivirais/análise , Deltaretrovirus/imunologia , Reservatórios de Doenças , HIV/imunologia , Anticorpos Anti-HIV , Humanos , Itália , Leucemia de Células Pilosas/epidemiologia , Fatores de RiscoRESUMO
Loss of heterozygosity (LOH) on chromosome 17q21 has been detected in 30% of primary human breast tumours. The smallest common region deleted occurred in an interval between the D17S746 and D17S846 polymorphic sequences tagged sites that are located on two recombinant P1-bacteriophage clones of chromosome 17q21: 122F4 and 50H1, respectively. To identify the target gene for LOH, we defined a map of this chromosomal region. We found the following genes: JUP, FK506BP10, SC65, Gastrin (GAS) and HAP1. Of the genes that have been identified in this study, only JUP is located between D17S746 and D17S846. This was of interest since earlier studies have shown that JUP expression is altered in breast, lung and thyroid tumours as well as cell lines having LOH in chromosome 17q21. However, no mutations were detected in JUP using single-strand conformation polymorphism analysis of primary breast tumour DNAs having LOH at 17q21. We could find no evidence that the transcription promoter for JUP is methylated in tumour DNAs having LOH at 17q21. We suspect that the target gene for LOH in primary human breast tumours on chromosome 17q21 is either JUP and results in a haploinsufficiency for expression or may be an unidentified gene located in the interval between D17S846 and JUP.
Assuntos
Neoplasias da Mama/genética , Cromossomos Humanos Par 17/genética , Proteínas do Citoesqueleto/genética , Perda de Heterozigosidade , Mapeamento Cromossômico , Análise Mutacional de DNA , Desmoplaquinas , Feminino , Humanos , Polimorfismo Conformacional de Fita Simples , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
Cell kinetics is a predictive parameter of breast-cancer aggressiveness, and mutations occurring in mammary tumorigenesis may favor uncontrolled cell proliferation. In this study, cell kinetics, clinico-pathological characteristics and genetic alterations at the int-2, bcl-1, c-myc, c-erbB-2, and DF3 loci were analyzed and correlated in 54 primary breast carcinomas. The occurrence of mutations at more than one locus was also studied. Tumor-proliferative activity was evaluated by determination of the thymidine labeling index (TLI). Amplification (AMP) of int-2 was observed in 11.2%, of bcl-1 in 9.4%, of c-myc in 5.7% and of c-erbB-2 in 8.6% of the carcinomas. Loss of heterozygosity (LOH) at the DF3 locus was detected in 13.9% of the tumors. Genetic alterations demonstrated a significant association with patient's age and high TLI values. AMP and LOH+AMP did not appear to be statistically related to histotype, histological grade, tumor size or lymph-node status. Alone, allele loss at the DF-3 locus was not significantly associated with any of the clinico-pathological characteristics studied. Alterations at more than one locus, including int-2/bcl-1, int-2/c-myc, int-2/bcl-1/c-erbB-2, and c-myc/DF3, were detected in 11.1% of the tumors. Multiple mutations were found only in less differentiated tumors, which included the 2 cases from the youngest patients of the series.
Assuntos
Neoplasias da Mama/genética , Neoplasias da Mama/patologia , Amplificação de Genes , Deleção de Genes , Proto-Oncogenes , Adulto , Idoso , Ciclo Celular/fisiologia , Feminino , Heterozigoto , Humanos , Pessoa de Meia-Idade , MutaçãoRESUMO
Genomic instability plays a key role in hereditary nonpolyposis colorectal cancer and in a significant sub-set of non-hereditary colorectal tumors. Recent evidence suggests that microsatellite instability also occurs in various sub-sets of common, non-hereditary forms of extra-colorectal carcinoma. To investigate the role of microsatellite instability in breast cancer, and to correlate this type of alteration with clinico-pathological characteristics, including tumor proliferative activity, we analyzed the status of 8 different microsatellite loci in 28 cases of primary mammary carcinoma. For this purpose, microsatellite banding patterns were compared in paired breast-cancer/peripheral-blood DNA samples. Microsatellite instability was observed in 6/28 (21%) of the cases. Four of the 6 tumors had low proliferative activity, one had high proliferative activity, and in one case proliferative activity values were not available. All chromosomal loci investigated demonstrated microsatellite instability in one or more representative tumors of the series. Shifts in length larger than 2 bp were the most frequent change. Microsatellite instability significantly correlated with the lobular histotype, and with lymph-node involvement. A trend was also observed associating microsatellite instability and large tumor size.
Assuntos
Neoplasias da Mama/genética , Carcinoma Ductal de Mama/genética , Adulto , Idoso , Alelos , Sequência de Bases , Neoplasias da Mama/patologia , Carcinoma Ductal de Mama/patologia , Primers do DNA/química , DNA de Neoplasias/genética , Feminino , Marcadores Genéticos , Humanos , Metástase Linfática , Pessoa de Meia-Idade , Dados de Sequência Molecular , Sequências Repetitivas de Ácido Nucleico , Deleção de SequênciaRESUMO
We have analyzed the functional activity of the p53 tumor suppressor in human T-cell lymphotropic virus type 2 (HTLV-2)-transformed cells. Abundant levels of the p53 protein were detected in both HTLV-2A and -2B virus-infected cell lines. The p53 was functionally inactive, however, both in transient-transfection assays using a p53 reporter plasmid and in induction of p53-responsive genes in response to gamma irradiation. We further investigated HTLV-2A Tax and HTLV-2B Tax effects on p53 activity. Interestingly, although Tax-2A and -2B inactivate p53, the Tax-2A protein appears to inhibit p53 function less efficiently than either Tax-1 or Tax-2B. In transient-cotransfection assays, Tax-1 and Tax-2B inactivated p53 by 80%, while Tax2A reduced p53 activity by 20%. In addition, Tax-2A does not increase the steady-state level of cellular p53 as well as Tax-1 or -2B does in the same assays. Cotransfection assays demonstrated that Tax-2A could efficiently transactivate CREB-responsive promoters to the same level as Tax-1 and Tax-2B, indicating that the protein was functional. This report provides evidence of the first functional difference between the HTLV-2A and -2B subtypes. This comparison of the action of HTLV-1 and HTLV-2 Tax proteins on p53 function will provide important insights into the mechanism of HTLV transformation.