Targeted Delivery of Doxorubicin via Sterically Stabilized Immunoliposomes: Pharmacokinetics and Biodistribution in Tumor-bearing Mice

Purpose. To evaluate benefits in tumor localization, availability, and noncancerous organ distribution of doxorubicin (DOX) delivered via small (120 nm) sterically stabilized immunoliposomes targeted against a tumor-associated antigen in fibrosarcoma-bearing mice. Methods. DOX-loaded liposomes were prepared with (i) specific monoclonal IgG₃ antibody (32/2, D-SSIL-32/2); (ii) non-specific IgG₃ (D-SSIL-IgG); or (iii) no IgG (D-SSL) on their surface. Equal DOX amounts were injected intravenously via each type of liposome into BALB/c mice carrying experimental lung metastases of a polyoma virus-induced fibrosarcoma (A9 etc 220) expressing a polyoma virus-induced tumor-associated antigen (PAA) on their surface. Metastases occurred mainly in lung. Mice were treated at 3 stages of tumor development (micrometastases, medium-size metastases, and large, necrotic metastases). Performance evaluation was based on time-dependent quantification of DOX and DOX metabolites (DOX-M) in lung tumor, noncancerous organs, and plasma. Results. (i) DOX delivered via both SSIL retained the prolonged circulation time typical of DOX delivered via D-SSL. (ii) DOX accumulation in noncancerous organs was similar for all preparations. Low levels of DOX-M were obtained for all three preparations in all organs except liver, suggesting a similar processing, (iii) Preparations differed in behavior in lung tumor depending on tumor size and microanatomy. Only at the micrometastases stage were the specifically targeted D-SSIL-32/2 superior to D-SSL and D-SSIL-IgG, delivering 2–4 times more drug into the tumor, (iv) DOX-M level in all three tumor stages was in the following order: D-SSIL-32/2 >> D-SSL >> D-SSIL-IgG, suggesting that DOX delivered as D-SSIL-32/2 is most available to tumor cells. Conclusions. The advantage of specific targeting of sterically stabilized liposomes is expressed mainly in increasing availability of DOX to tumor cells in a way which is dependent on tumor microanatomy. The impact of this advantage to therapeutic efficacy remains to be determined.     

Likelihood ratios for mixed stains when the number of donors cannot be agreed

Suppose that part of the prosecution's evidence in some crime case is analysis of a blood stain, and that the traits E discovered in the stain suggest multiple donors. Then the prosecution will probably allege some specific inculpatory hypothesis H₀ about the sources of the stain, and P {E | H₀} can be calculated. It is desirable to use this as the numerator of a likelihood ratio. However, in general the obvious denominator P {E | H₀} cannot be calculated, so unless the defense is sufficiently obliging as to stipulate to a specific choice among the potentially infinite number of more or less exculpatory alternative hypotheses, the desired likelihood ratio can't be evaluated. We show that nonetheless, in most cases there is an adequate inequality.     

Apathetic hyperthroidism

Among the psychosyndromes least well known to be associated with an endocrinopathy is apathetic hyperthyroidism. This condition is characterized by apathy, lethargy, severe "senile depression" and often a high output cardiac failure occurring as the presenting problem.1,2,9 The depressive component of the clinical picture may occur without cardiac complications. Such depressions in the elderly, while refractory to treatment with antidepressant drugs, often respond dramatically to the correction of the underlying endocrine dysfunction.4 It is therefore important to consider "thyroid melancholia" in the differential diagnosis of such cases. Given this high index of suspicion, the diagnosis can be fairly easily made.     

Interleukin 2 and the treatment of leukemia and lymphoma

As evidence has accumulated that allogeneic bone marrow transplantation provides therapeutic benefit by means of a graft versus malignancy effect, there has been a corresponding increase in interest in inducing or enhancing such an effect after chemotherapy and/or autologous bone marrow transplantation. Administration of Interleukin-2 may be one way of achieving this aim. Recent studies have shown the cytokine is tolerated after ABMT/chemotherapy in immunomodulatory doses and that the MHC unrestricted cytotoxic effector mechanisms induced can indeed discriminate between normal and malignant tissue. As always, larger scale randomized studies will be required before the therapeutic efficacy of this approach can been assessed.     

Fractionated high dose-rate versus low dose-rate regimens for intracavitary brachytherapy of the cervix: equivalent regimens for combined brachytherapy and external irradiation

The conventional treatment for carcinoma of the uterine cervix is a combination of external teletherapy and low dose-rate (LDR) intracavitary brachytherapy. Recently, however, there has been an increasing trend toward the use of high dose-rate (HDR) brachytherapy, in combination with external irradiation. The question is addressed of designing HDR treatments that will produce equivalent results to the more conventional protocols. We argue that for the unique case of radiotherapeutic treatment of carcinoma of the cervix, the criterion for producing an equivalent treatment should be based on the matching of early, not late, effects. In essence, this is because the dose to the tissues at risk for late effects is usually significantly smaller than the prescribed dose. When this effect is factored in with the different shape of dose-response curves for early and late effects, we conclude that, in the majority of cases, late effects will be no worse in a HDR regimen than a LDR regimen, provided that the corresponding doses have been matched to produce equal early effects. We provide a formalism whereby equivalent protocols can be designed for combined "external + HDR brachytherapy" regimens to match current "external + LDR brachytherapy" schedules. Using extensive basic radiobiological in vitro data derived from various cells of human origin, we provide specific examples of equivalent "external + HDR brachytherapy" regimens for 23 current "external + LDR brachytherapy" commonly-used schedules.     

Determination of glomerular size-selectivity in the normal rat with Ficoll.

Diffusion studies in vitro indicate that Ficoll behaves more like an ideal spherical molecule than does dextran, suggesting that Ficoll would be a better probe of glomerular pore size than the commonly used dextran. To examine the differences between these macromolecules in vivo, the fractional clearances of tritiated Ficoll and dextran were measured over a wide range of molecular sizes (Stokes-Einstein radius, rs, from 19 to 65 A) in normal euvolemic Munich-Wistar rats. Whole-kidney and single-nephron hemodynamic conditions were characterized through a combination of clearance and micropuncture measurements. The fractional clearance, or sieving coefficient (theta), for dextran significantly exceeded that of Ficoll at all molecular sizes examined, theta for dextran being approximately 10 times that for Ficoll for rs greater than 30 A. Thus, the results with Ficoll imply a more size-restrictive barrier than do the results with dextran. The values of theta for Ficoll approximated previously reported values for uncharged globular proteins. Although theta for Ficoll at rs = 35 A was much smaller than the corresponding value for dextran, it was still approximately 30 times greater than typical values of the filtrate-to-plasma concentration ratio reported for serum albumin (a polyanion) in the rat, in agreement with the concept that glomerular charge-selectivity normally plays an important role in the prevention of albuminuria. Three membrane-pore models were compared in their ability to represent the dextran and Ficoll sieving data. A lognormal pore-size distribution in parallel with a nonselective "shunt" pathway was found to be more effective than either an isoporous membrane with a shunt or a purely lognormal distribution. On the basis of these laboratory results and computations, Ficoll may be preferred over dextran in future studies of glomerular size-selectivity.     

Mast cell activity in experimental allergic encephalomyelitis

The number and functional reactivity of peritoneal mast cells (MCs) were evaluated in rats with experimental allergic encephalomyelitis (EAE). Cells were counted following staining with toluidine blue and activation was measured by B-hexosaminidase (B-hex) release. The number of detectable MCs and their capacity to release B-hex decreased significantly by 40 and 65%, respectively, as compared with normal controls just prior to the onset of clinical signs. These values returned to normal on clinical recovery. Preliminary data on MC counts performed on histological sections of rat brains with EAE suggested a similar pattern of response, i.e., an early decrease prior to disease onset with subsequent normalization on recovery. In an attempt to modify the course of EAE, rats were treated with the MC stabilizing agent nedocromil or with the MC activating agent, compound 48/80. Nedocromil induced a slight delay in the onset of EAE, but only when administered at the time of EAE induction. Compound 48/80 did not seem to affect the clinical course of the disease. Our results suggest that MCs are involved in the pathogenesis of EAE and may contribute to the induction of the disease rather than to the effector phase and its clinical expression.     

The heterogeneity of leukemic reticuloendotheliosis, "hairy cell leukemia". Evidence for its monocytic origin.

The presence of B, T, and monocyte markers were studied on the spleen and peripheral blood mononuclear cells from two patients with leukemic reticuloendotheliosis. A high proportion of cells from both patients bore a receptor for cytophilic antibody, both in suspension and frozen tissue section. Cells in suspension lacked surface immunoglobulins or a receptor for sheep red blood cells. These results favor the evidence that "hairy cells" are monocytic in origin.     

Salicylate enhances necrosis and apoptosis mediated by the mitochondrial permeability transition.

Onset of the mitochondrial permeability transition (MPT) causes both necrotic and apoptotic cell death in cultured hepatocytes. Salicylate lowers the threshold for onset of the MPT. In this study, our aim was to determine whether nontoxic concentrations of salicylate potentiate MPT-mediated cell killing. In necrotic killing models to rat hepatocytes, salicylate (1 mM) enhanced calcium ionophore (Br-A23187)- and tert-butylhydroperoxide (t-BuOOH)-induced cell death, which was blocked or delayed by cyclosporin A (CsA, 2 microM), a specific inhibitor of the MPT. In hepatocyte apoptosis induced by tumor necrosis factor-alpha (TNF-alpha), salicylate accelerated cell killing after low-dose TNF-alpha (1 ng/ml), which by itself induced little apoptosis. Salicylate enhancement of apoptosis was associated with onset of the MPT and accelerated caspase 3 activation. Salicylate also augmented killing of MCF-7 human breast tumor cells by etoposide and PLC/PRF/5 human hepatoma cells by tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). In conclusion, salicylate potentiates both necrotic and apoptotic cell killing by promoting onset of the MPT. Enhancement by salicylate of MPT-dependent apoptosis may play a role in protection by aspirin and other nonsteroidal anti-inflammatory drugs against colon, lung, and breast cancer.