The impact of demographic and clinical characteristics on the trajectories of health-related quality of life among patients with Fabry disease.

BACKGROUND: Fabry disease (FD) is an X-linked lysosomal storage disorder characterized by multiorgan dysfunction. Since individuals with FD usually experience progressive clinical disease manifestations, their health-related quality of life (HRQOL) is expected to change over time. However, there is limited longitudinal research examining HRQOL outcomes in individuals with FD. We aimed to: assess longitudinal outcomes in HRQOL in adults with FD; examine the physical- and mental HRQOL trajectories at the initial registration (baseline), 3-5 year, and 7-13 year follow-ups; and evaluate the possible associations of age, sex and medical complications with the physical- and mental HRQOL trajectories. METHODS: Forty-three individuals with FD (53% female) who were aged 18 to 81 years at baseline attended clinical follow-up visits between 2006 and 2020. Medical records were extracted retrospectively. Demographics and the 36-item Short-Form Health Survey (SF-36) were recorded at scheduled visits, except for the last data collection which was prospectively obtained in 2020. The physical (PCS) and mental (MCS) composite scores (SF-36) were chosen as outcome measures. RESULTS: The eight SF-36 domain scores were stable over a span of 13 years, and only physical- and social functioning domains worsened clinically over this follow-up period. Mean baseline SF-36 domain scores were all significantly lower (decreased HRQOL) in the FD sample compared with Norwegian population norms. Two hierarchical linear models were run to examine whether demographics and medical complications (measured at the last clinical visit) predicted physical and mental HRQOL trajectories. Age above 47 years (p < 0.001), male sex (p = 0.027), small fibre neuropathy (p < 0.001), renal dysfunction (p < 0.001), and cerebrovascular events (p = 0.003) were associated with lower HRQOL over time. No significant interactions were found between the time of follow up and the abovementioned predictors of HRQOL. CONCLUSIONS: Overall HRQOL trajectories remained stable between baseline, 3-5 year, and 7-13 year follow-ups, with the majority of individuals reporting decreased physical and mental HRQOL. Medical complications in combination with older age and male sex are important predictors of lower HRQOL in FD. Awareness of this relationship is valuable both for health care providers and for patients. The findings provide indicators that can guide treatment decisions to improve physical and mental HRQOL outcomes.

Systematic screening for atrial fibrillation in a 65-year-old population with risk factors for stroke: data from the Akershus Cardiac Examination 1950 study.

Aims: To investigate the yield of screening for atrial fibrillation (AF) in a cohort of 65-year-old individuals from the general population with additional risk factors for stroke. Methods and results: We invited participants with additional risk factors for stroke (CHA2DS2-VASc score ≥2 for men or ≥ 3 for women) without previously known AF from a population-based study in Norway to participate in a 2-week screening for AF. Screening was performed by one-lead 'thumb electrocardiography (ECG)' recordings of 30 s twice daily or when the participants experienced symptoms. In total, 1742 (47.0%) participants of the Akershus Cardiac Examination (ACE) 1950 study had at least one additional risk factor for stroke. Of these, 123 cases reported a history of AF and 101 (5.8%) cases were ECG validated. Eight [0.5%, 95% confidence interval (CI) 0.2-0.9] new AF cases were diagnosed by 12-lead ECG at baseline, and 10 additional participants were diagnosed with AF before screening commenced. We invited all 1601 participants who met the inclusion criteria for screening, of which 1510 (94.3%) participants were included (44% women and 56% men). The screening revealed AF in 13 (0.9%, 95% CI 0.5-1.5) participants. The total prevalence of ECG-validated AF after screening among the 65-year-olds with risk factors for stroke was 7.6% (95% CI 6.4-8.9), in men 10.0% (95% CI 8.2-12.0), and in women 4.3% (95% CI 3.0-6.1) (P < 0.001). Conclusion: In a group of 1510 well-characterized 65-year-olds with risk factors for stroke, 2-week intermittent ECG screening identified undiagnosed AF in 0.9%. The total prevalence of AF was 7.6%.

Association Between Pretransplant Cancer and Survival in Kidney Transplant Recipients.

BACKGROUND: Kidney transplantation in recipients with a previous malignancy is often deferred 2 to 5 years after cancer treatment due to fear of cancer recurrence. In Norway, the required waiting period has been 1 year. METHODS: We compared patient and graft survival of recipients with pretransplant cancer to the outcomes of matched recipients without such cancer (comparators) using Cox regression. RESULTS: From 1963 to 2010, 377 (6.4%) of 5867 recipients had a pretransplant cancer. During a median follow-up of 6.8 years, 256 recipients died, 35 (13.7%) from recurrent cancer and 27 (10.5%) from de novo cancer. Uncensored and death-censored graft loss occurred in 263 and 46 recipients, respectively. All-cause mortality was similar as in comparators (hazard ratio [HR], 1.06; 95% confidence interval [CI], 0.93-1.20]; P = 0.40), death-censored graft loss was lower (HR, 0.63; 95% CI, 0.47-0.84; P = 0.002), and uncensored graft loss was similar (HR, 0.99; 95% CI, 0.87-1.12; P = 0.87). Cancer mortality was higher than in comparators (HR, 1.97; 95% CI, 1.51-2.56; P < 0.001), particularly during the first 5 years of follow-up (HR, 3.44; 95% CI, 2.36-5.03; P < 0.01). Waiting period was not associated with recurrent cancer mortality or all-cause mortality (both P > 0.45). Results were similar within cancer subgroups, with most data in patients with a history of kidney cancer, prostate cancer, urothelial cancer, and skin squamous cell carcinoma. CONCLUSIONS: Kidney transplant recipients with a pretransplant cancer had a similar overall patient and graft survival as recipients without such cancer. Cancer mortality was increased, particularly during the first 5 years after transplantation. A short waiting period was not associated with mortality.

Tumour-associated glial host cells display a stem-like phenotype with a distinct gene expression profile and promote growth of GBM xenografts.

BACKGROUND: Little is known about the role of glial host cells in brain tumours. However, supporting stromal cells have been shown to foster tumour growth in other cancers. METHODS: We isolated stromal cells from patient-derived glioblastoma (GBM) xenografts established in GFP-NOD/scid mice. With simultaneous removal of CD11b+ immune and CD31+ endothelial cells by fluorescence activated cell sorting (FACS), we obtained a population of tumour-associated glial cells, TAGs, expressing markers of terminally differentiaed glial cell types or glial progenitors. This cell population was subsequently characterised using gene expression analyses and immunocytochemistry. Furthermore, sphere formation was assessed in vitro and their glioma growth-promoting ability was examined in vivo. Finally, the expression of TAG related markers was validated in human GBMs. RESULTS: TAGs were highly enriched for the expression of glial cell proteins including GFAP and myelin basic protein (MBP), and immature markers such as Nestin and O4. A fraction of TAGs displayed sphere formation in stem cell medium. Moreover, TAGs promoted brain tumour growth in vivo when co-implanted with glioma cells, compared to implanting only glioma cells, or glioma cells and unconditioned glial cells from mice without tumours. Genome-wide microarray analysis of TAGs showed an expression profile distinct from glial cells from healthy mice brains. Notably, TAGs upregulated genes associated with immature cell types and self-renewal, including Pou3f2 and Sox2. In addition, TAGs from highly angiogenic tumours showed upregulation of angiogenic factors, including Vegf and Angiopoietin 2. Immunohistochemistry of three GBMs, two patient biopsies and one GBM xenograft, confirmed that the expression of these genes was mainly confined to TAGs in the tumour bed. Furthermore, their expression profiles displayed a significant overlap with gene clusters defining prognostic subclasses of human GBMs. CONCLUSIONS: Our data demonstrate that glial host cells in brain tumours are functionally distinct from glial cells of healthy mice brains. Furthermore, TAGs display a gene expression profile with enrichment for genes related to stem cells, immature cell types and developmental processes. Future studies are needed to delineate the biological mechanisms regulating the brain tumour-host interplay.

Risk factors for hip-related clinical signs in a prospective cohort study of four large dog breeds in Norway.

We conducted a prospective cohort study including privately owned dogs from the breeds Newfondland (NF), Labrador Retriever (LR), Leonberger (LEO), and Irish Wolfhound (IW) followed from birth until age 9 yrs. We wanted to investigate whether radiological hip dysplasia status given at approximately age 12-18 mos and other factors during growth influenced development of clinical signs due to hip-joint disease necessitating veterinary consultation. Whether or not such signs occurred due to hip dysplasia or due to secondary or primary DJD could not be distinguished, and we therefore used the term "owner-reported veterinary-diagnosed hip-related clinical signs" ("the event"). The included dogs were followed from birth to the event or until a maximum of 9 yrs of age. Our objectives were to describe breed differences in time to incidence and to evaluate potential risk factors for the time to event. We used Kaplan-Meier curves to describe time to incidence, and potential risk factors were assessed by use of a Cox proportional-hazards model. We enrolled 494 dogs from 103 litters, and 46 dogs were reported as having had the event during the observation period. We observed a significant time-varying effect (TVE): LR and LEO developed clinical signs later in life than NF. If the radiological hip status was either mild, moderate, or severe the hazard of experiencing the event was significantly increased. Access to off-leash exercise at age 12 mos decreased the hazard of the event, and the hazard varied by litter. The findings supported the hypothesis that radiological hip status at screening and exercise conditions during growth influenced the time to incidence of the event and that there were breed differences in time to the event.

A prospective study on canine hip dysplasia and growth in a cohort of four large breeds in Norway (1998-2001).

The study-objective was to measure the effect of weight and growth related parameters on the risk of development of Canine Hip Dysplasia (CHD). The hypothesis was that heavy and fast growing dogs of large sized breeds were at increased risk of development of CHD compared to lighter and slower growing dogs. A prospective cohort study was conducted among dogs of four large breeds: Newfoundland (NF), Leonberger (LEO), Labrador retriever (LR), and Irish wolfhound (IW). The dogs were privately owned with individualized nutrition and environment, and they were followed from birth and throughout the growth period until the official screening for CHD was performed. The study sample consisted of 501 dogs from 103 litters, with the breed distribution 125 NF, 180 LEO, 133 LR, and 63 IW. Because the dogs were clustered in litters a multivariable random effects logistic regression model was used to assess statistically significant growth-related risk factors for CHD. The estimated incidence risk of CHD was 36% in NF, 25% in LEO, 20% in LR, and 10% in IW. Based upon the final multilevel model it appears that the odds of CHD among both LR and IW (odds ratio (OR) 0.22) are about one-fifth of the odds for NF. The odds for LEO (OR 0.60) are not significantly different from NF. There appeared to be an inverse relationship between body weight at 3 months of age and odds of CHD, with an OR of 0.89 (P=0.044). The degree of clustering at the litter-level was high (22.6%) and highly significant (P<0.001). Findings failed to support the hypothesis that heavy and fast growing dogs from four large sized breeds were at increased risk for development of CHD. There might be other unmeasured environmental risk factors for CHD in this cohort of dogs, although the contribution of the genetic variance to the litter-level clustering also needs further investigation.

Adaptive radiotherapy based on contrast enhanced cone beam CT imaging.

Cone beam CT (CBCT) imaging has become an integral part of radiation therapy, with images typically used for offline or online patient setup corrections based on bony anatomy co-registration. Ideally, the co-registration should be based on tumor localization. However, soft tissue contrast in CBCT images may be limited. In the present work, contrast enhanced CBCT (CECBCT) images were used for tumor visualization and treatment adaptation. Material and methods. A spontaneous canine maxillary tumor was subjected to repeated cone beam CT imaging during fractionated radiotherapy (10 fractions in total). At five of the treatment fractions, CECBCT images, employing an iodinated contrast agent, were acquired, as well as pre-contrast CBCT images. The tumor was clearly visible in post-contrast minus pre-contrast subtraction images, and these contrast images were used to delineate gross tumor volumes. IMRT dose plans were subsequently generated. Four different strategies were explored: 1) fully adapted planning based on each CECBCT image series, 2) planning based on images acquired at the first treatment fraction and patient repositioning following bony anatomy co-registration, 3) as for 2), but with patient repositioning based on co-registering contrast images, and 4) a strategy with no patient repositioning or treatment adaptation. The equivalent uniform dose (EUD) and tumor control probability (TCP) calculations to estimate treatment outcome for each strategy. Results. Similar translation vectors were found when bony anatomy and contrast enhancement co-registration were compared. Strategy 1 gave EUDs closest to the prescription dose and the highest TCP. Strategies 2 and 3 gave EUDs and TCPs close to that of strategy 1, with strategy 3 being slightly better than strategy 2. Even greater benefits from strategies 1 and 3 are expected with increasing tumor movement or deformation during treatment. The non-adaptive strategy 4 was clearly inferior to all three adaptive strategies. Conclusion. CECBCT may prove useful for adaptive radiotherapy.

Genomic aberrations in borderline ovarian tumors.

BACKGROUND: According to the scientific literature, less than 30 borderline ovarian tumors have been karyotyped and less than 100 analyzed for genomic imbalances by CGH. METHODS: We report a series of borderline ovarian tumors (n = 23) analyzed by G-banding and karyotyping as well as high resolution CGH; in addition, the tumors were analyzed for microsatellite stability status and by FISH for possible 6q deletion. RESULTS: All informative tumors were microsatellite stable and none had a deletion in 6q27. All cases with an abnormal karyotype had simple chromosomal aberrations with +7 and +12 as the most common. In three tumors with single structural rearrangements, a common breakpoint in 3q13 was detected. The major copy number changes detected in the borderline tumors were gains from chromosome arms 2q, 6q, 8q, 9p, and 13q and losses from 1p, 12q, 14q, 15q, 16p, 17p, 17q, 19p, 19q, and 22q. The series included five pairs of bilateral tumors and, in two of these pairs, informative data were obtained as to their clonal relationship. In both pairs, similarities were found between the tumors from the right and left side, strongly indicating that bilaterality had occurred via a metastatic process. The bilateral tumors as a group showed more aberrations than did the unilateral ones, consistent with the view that bilaterality is a sign of more advanced disease. CONCLUSION: Because some of the imbalances found in borderline ovarian tumors seem to be similar to imbalances already known from the more extensively studied overt ovarian carcinomas, we speculate that the subset of borderline tumors with detectable imbalances or karyotypic aberrations may contain a smaller subset of tumors with a tendency to develop a more malignant phenotype. The group of borderline tumors with no imbalances would, in this line of thinking, have less or no propensity for clonal evolution and development to full-blown carcinomas.

Chronic myelogenous leukemia with the e6a2 BCR-ABL and lacking imatinib response: presentation of two cases.

The BCR-ABL fusion gene represents the hallmark of chronic myelogenous leukemia (CML) and is derived from a translocation between chromosome 9 and 22. The majority of CML patients have a breakpoint in the major BCR region of the BCR gene giving rise to e13a2 or e14a2 BCR-ABL transcripts. Occasionally, other BCR breakpoints occur. The current report describes two e6a2 CML patients with imatinib treatment failure and unusual disease progression. One patient was Philadelphia chromosome positive and one was Philadelphia chromosome negative with an atypical BCR-ABL rearrangement, ins (22;9).

Radiotherapy adapted to spatial and temporal variability in tumor hypoxia.

PURPOSE: To explore the feasibility and clinical potential of adapting radiotherapy to temporal and spatial variations in tumor oxygenation. METHODS AND MATERIALS: Repeated dynamic contrast enhanced magnetic resonance (DCEMR) images were taken of a canine sarcoma during the course of fractionated radiation therapy. The tumor contrast enhancement was assumed to represent the oxygen distribution. The IMRT plans were retrospectively adapted to the DCEMR images by employing tumor dose redistribution. Optimized nonuniform tumor dose distributions were calculated and compared with a uniform dose distribution delivering the same integral dose to the tumor. Clinical outcome was estimated from tumor control probability (TCP) and normal tissue complication probability (NTCP) modeling. RESULTS: The biologically adapted treatment was found to give a substantial increase in TCP compared with conventional radiotherapy, even when only pretreatment images were used as basis for the treatment planning. The TCP was further increased by repeated replanning during the course of treatment, and replanning twice a week was found to give near optimal TCP. Random errors in patient positioning were found to give a small decrease in TCP, whereas systematic errors were found to reduce TCP substantially. NTCP for the adapted treatment was similar to or lower than for the conventional treatment, both for parallel and serial normal tissue structures. CONCLUSION: Biologically adapted radiotherapy is estimated to improve treatment outcome of tumors having spatial and temporal variations in radiosensitivity.

Differential activities of alpha/beta IFN subtypes against influenza virus in vivo and enhancement of specific immune responses in DNA vaccinated mice expressing haemagglutinin and nucleoprotein.

Vaccines are urgently needed to elicit immunity to different influenza virus strains. DNA vaccines can elicit partial protective immunity, however their efficacy requires improvement. We assessed the capacity of individual type I IFN multigene family members as subtype transgenes to abrogate influenza virus replication in a vaccination/challenge mouse model. Differences in antiviral efficacy were found among the subtypes with IFNA5 and IFNA6 being most effective, while IFNA1 was the least effective in reducing lung virus replication. Mice vaccinated with combinatorial HA/IFNA6 or NP/IFNA6 showed reduced lung viral titres, clinical score, body weight loss, and pulmonary tissue damage compared to IFNA6, HA, or NP viral vaccination alone. In addition, IFNA6 increased IgG2a titres with upregulation of IFN-gamma response in the respiratory tract. We conclude that IFN-alpha 6 has antiviral and immunomodulatory effects, which improve efficacy of DNA vaccines for enhanced control of influenza.

A novel regulatory mechanism couples deoxyribonucleotide synthesis and DNA replication in Escherichia coli.

We present evidence for a complex regulatory interplay between the initiation of DNA replication and deoxyribonucleotide synthesis. In Escherichia coli, the ATP-bound DnaA protein initiates chromosomal replication. Upon loading of the beta-clamp subunit (DnaN) of the replicase, DnaA is inactivated as its intrinsic ATPase activity is stimulated by the protein Hda. The beta-subunit acts as a matchmaker between Hda and DnaA. Chain elongation of DNA requires a sufficient supply of deoxyribonucleotides (dNTPs), which are produced by ribonucleotide reductase (RNR). We present evidence suggesting that the molecular switch from ATP-DnaA to ADP-DnaA is a critical step coordinating DNA replication with increased deoxyribonucleotide synthesis. Characterization of dnaA and dnaN mutations that result in a constitutively high expression of RNR reveal this mechanism. We propose that the nucleotide bound state of DnaA regulates the transcription of the genes encoding ribonucleotide reductase (nrdAB). Accordingly, the conversion of ATP-DnaA to ADP-DnaA after initiation and loading of the beta-subunit DnaN would allow increased nrdAB expression, and consequently, coordinated RNR synthesis and DNA replication during the cell cycle.

Phase 1/2 trial of autologous tumor mixed with an allogeneic GVAX vaccine in advanced-stage non-small-cell lung cancer.

Tumor vaccines composed of autologous tumor cells genetically modified to secrete granulocyte-macrophage colony-stimulating factor (GM-CSF) (GVAX) have demonstrated clinical activity in advanced-stage non-small-cell lung cancer (NSCLC). In an effort to remove the requirement for genetic transduction of individual tumors, we developed a 'bystander' GVAX platform composed of autologous tumor cells mixed with an allogeneic GM-CSF-secreting cell line. We conducted a phase I/II trial of this vaccine (3-12 biweekly vaccinations) in advanced-stage NSCLC. Tumors were harvested from 86 patients, tumor cell processing was successful in 76, and 49 proceeded to vaccination. The most common toxicity was local vaccine injection site reactions. Serum GM-CSF pharmacokinetics were consistent with secretion of GM-CSF from vaccine cells for up to 4 days with associated transient leukocytosis confirming the bioactivity of vaccine-secreted GM-CSF. Evidence of vaccine-induced immune activation was demonstrated; however, objective tumor responses were not seen. Compared with autologous GVAX vaccines prepared by transduction of individual tumors with an adenoviral GM-CSF vector, vaccine GM-CSF secretion was approximately 25-fold higher with the bystander GVAX vaccine used in this trial. However, the frequency of vaccine site reactions, tumor response, time to disease progression, and survival were all less favorable in the current study.

Fluctuations in pO2 in poorly and well-oxygenated spontaneous canine tumors before and during fractionated radiation therapy.

BACKGROUND AND PURPOSE: The spatial heterogeneity in oxygen tension (pO2) in tumor tissue has been studied extensively, whereas, the information about the temporal heterogeneity is sparse. The purpose of the present study was to search for pO2 fluctuations in untreated and irradiated spontaneous canine tumors, and to investigate whether there is a relationship between overall tumor oxygenation status and pO2 fluctuation pattern. PATIENTS AND METHODS: Six dogs scheduled for radiation therapy of head and neck cancer were included in the study. The primary tumors were irradiated with 18 fractions of 3 Gy. Eppendorf polarographic electrodes and OxyLite fluorescence probes were used to measure overall oxygenation status and pO2 fluctuation pattern, respectively. Tissue pO2 was recorded at three subsequent days prior to treatment, and immediately before radiation fraction 4, 7, and 10. RESULTS: Overall oxygenation status differed substantially among the tumors. Radiation therapy had no consistent effect on overall oxygenation status. Fluctuations in pO2 were detected in untreated as well as irradiated tumors, and independent of whether the tumors were poorly or well oxygenated. CONCLUSIONS: Fluctuations in pO2 can occur in untreated and irradiated spontaneous canine tumors. There is no correlation between pO2 fluctuation pattern and overall tumor oxygenation status.

Long-term in vivo survival of receptor-modified syngeneic T cells in patients with human immunodeficiency virus infection.

To study human immunodeficiency virus (HIV)-specific cellular immunity in vivo, we transferred syngeneic lymphocytes after ex vivo expansion and transduction with a chimeric receptor gene (CD4/CD3-zeta) between identical twins discordant for HIV infection. Single and multiple infusions of 10(10) genetically modified CD8(+) T cells resulted in peak fractions in the circulation of approximately 10(4) to 10(5) modified cells/10(6) mononuclear cells at 24 to 48 hours, followed by 2- to 3-log declines by 8 weeks. In an effort to provide longer high-level persistence of the transferred cells and possibly enhance anti-HIV activity, we administered a second series of infusions in which both CD4(+ )and CD8(+) T cells were engineered to express the chimeric receptor and were costimulated ex vivo with beads coated with anti-CD3 and anti-CD28. Sustained fractions of approximately 10(3) to 10(4) modified cells/10(6) total CD4(+) or CD8(+) cells persisted for at least 1 year. Assessment of in vivo trafficking of the transferred cells by lymphoid tissue biopsies revealed the presence of modified cells in proportions equivalent to or below those in the circulation. The cell infusions were well tolerated and were not associated with substantive immunologic or virologic changes. Thus, adoptive transfer of genetically modified HIV-antigen-specific T cells was safe. Sustained survival in the circulation was achieved when modified CD4(+ )and CD8(+) T cells were infused together after ex vivo costimulation, indicating the important role played by antigen-specific CD4(+) T cells in providing "help" to cytotoxic effectors. (Blood. 2000;96:467-474)

Systemic T cell-independent tumor immunity after transplantation of universal receptor-modified bone marrow into SCID mice.

Gene modification of hematopoietic stem cells (HSC) with antigen-specific, chimeric, or "universal" immune receptors (URs) is a novel but untested form of targeted immunotherapy. A human immunodeficiency virus (HIV) envelope-specific UR consisting of the extracellular domain of human CD4 linked to the zeta chain of the T cell receptor (CD4 zeta) was introduced ex vivo into murine HSC by retroviral transduction. After transplantation into immunodeficient SCID mice, sustained high level expression of CD4 zeta was observed in circulating myeloid and natural killer cells. CD4 zeta-transplanted mice were protected from challenge with a lethal dose of a disseminated human leukemia expressing HIV envelope. These results demonstrate the ability of chimeric receptors bearing zeta-signaling domains to activate non-T cell effector populations in vivo and thereby mediate systemic immunity.

T-cell gene therapy.

In the past year, a number of human gene therapy trials involving the adoptive transfer of genetically modified T lymphocytes have been reported. These include trials of adenosine deaminase gene transfer in children with severe combined immunodeficiency syndrome, a gene-marking study of Epstein-Barr virus-specific cytotoxic T cells, and trials of gene-modified T cells expressing suicide or viral resistance genes in patients infected with HIV. Additional strategies for T-cell gene therapy currently being pursued in the clinic involve the engineering of novel T-cell receptors that impart antigen specificity for virally infected or malignant cells.

Comparison of anti-Tac and anti-transferrin receptor-conjugated liposomes for specific drug delivery to adult T-cell leukemia.

Adult T-cell leukemia (ATL) is a rapidly progressive and usually fatal malignancy of mature T cells characterized by the expression of large numbers of interleukin-2 (IL-2) receptors on the cell surface. Anti-Tac, a monoclonal antibody directed against the IL-2 receptor, was conjugated to liposomes and compared with anti-transferrin receptor (anti-TFR) conjugates for specific binding, internalization, and intracellular drug delivery to ATL cells. Two independent assays were used: a fluorimetric assay with liposome encapsulated 1-hydroxypyrene-3,6,8-trisulfonic acid, a pH-sensitive fluorescent dye, and a growth inhibition assay using methotrexate-gamma-aspartate, a liposome-dependent cytotoxic drug. MT-1 and HUT-102 cell lines derived from patients with ATL were compared with Molt-4, a leukemia cell line that does not express IL-2 receptors in an uninduced state. Fluorimetric studies showed specific binding and internalization of anti-Tac-conjugated liposomes by HUT-102 and MT-1 but not by the Tac-negative cell line Molt-4, demonstrating the lack of nonspecific or Fc receptor-mediated uptake. Anti-TFR-conjugated liposomes were effectively bound and internalized by all three cell lines and consistently showed the highest degree of cellular liposome uptake. Drug-containing liposomes conjugated to anti-Tac were more than tenfold more effective in causing growth inhibition of ATL cells than the nonspecific control conjugates. Anti-Tac conjugates caused minimal growth inhibition of Molt-4 cells over the concentration range effective against the ATL cells. Anti-TFR-coupled liposomes gave better growth inhibition of HUT-102 and MT-1 cells (40- to 60-fold) than anti-Tac conjugates. Both anti-Tac-directed and anti-TFR-directed liposomes are effective for intracellular drug delivery to ATL cells and may represent a useful method of treatment in this disease.