Drug targeting to tumors: principles, pitfalls and (pre-) clinical progress

Many different systems and strategies have been evaluated for drug targeting to tumors over the years. Routinely used systems include liposomes, polymers, micelles, nanoparticles and antibodies, and examples of strategies are passive drug targeting, active drug targeting to cancer cells, active drug targeting to endothelial cells and triggered drug delivery. Significant progress has been made in this area of research both at the preclinical and at the clinical level, and a number of (primarily passively tumor-targeted) nanomedicine formulations have been approved for clinical use. Significant progress has also been made with regard to better understanding the (patho-) physiological principles of drug targeting to tumors. This has led to the identification of several important pitfalls in tumor-targeted drug delivery, including I) overinterpretation of the EPR effect; II) poor tumor and tissue penetration of nanomedicines; III) misunderstanding of the potential usefulness of active drug targeting; IV) irrational formulation design, based on materials which are too complex and not broadly applicable; V) insufficient incorporation of nanomedicine formulations in clinically relevant combination regimens; VI) negligence of the notion that the highest medical need relates to metastasis, and not to solid tumor treatment; VII) insufficient integration of non-invasive imaging techniques and theranostics, which could be used to personalize nanomedicine-based therapeutic interventions; and VIII) lack of (efficacy analyses in) proper animal models, which are physiologically more relevant and more predictive for the clinical situation. These insights strongly suggest that besides making ever more nanomedicine formulations, future efforts should also address some of the conceptual drawbacks of drug targeting to tumors, and that strategies should be developed to overcome these shortcomings.     

Targeted deletion of ERK5 MAP kinase in the developing nervous system impairs development of GABAergic interneurons in the main olfactory bulb and behavioral discrimination between structurally similar odorants

ERK5 MAP kinase is highly expressed in the developing nervous system and has been implicated in promoting the survival of immature neurons in culture. However, its role in the development and function of the mammalian nervous system has not been established in vivo. Here, we report that conditional deletion of the erk5 gene in mouse neural stem cells during development reduces the number of GABAergic interneurons in the main olfactory bulb (OB). Our data suggest that this is due to a decrease in proliferation and an increase in apoptosis in the subventricular zone and rostral migratory stream of ERK5 mutant mice. Interestingly, ERK5 mutant mice have smaller OB and are impaired in odor discrimination between structurally similar odorants. We conclude that ERK5 is a novel signaling pathway regulating developmental OB neurogenesis and olfactory behavior.     

Health- related quality of life and self-worth in 10-year old children with congenital hypothyroidism diagnosed by neonatal screening

Background

Much is written about cognitive and motor development; less is known about social and emotional consequences of growing up with congenital hypothyroidism (CH). The objectives of the study were: (1) to compare health related quality of life (HRQoL) and self-worth of 10 year old patients with CH with the general population; (2) to explore associations of disease factors, IQ and motor skills with the outcomes.

Methods

Children with CH and their parents completed several questionnaires. Patients were classified to ‘severe CH, n?=?41’ or ‘moderate/mild CH, n?=?41’ based on pre-treatment FT4 concentration. Differences between CH and the general population were tested by analysis of covariance and one sample t-tests (mean scale scores HRQoL and self-worth), chi-square tests and binomial tests (% at risk of impaired HRQoL and self-worth). Linear regression analyses corrected for gender were conducted to explore associations of the outcomes with disease factors, IQ and motor skills.

Results

Patients with CH reported lower mean HRQoL on motor, cognitive and social functioning, and on autonomy and positive emotions (p?<?0.0001). Patients were also more often at risk for impaired HRQoL and self-worth. No differences were found between the severity groups. Lower IQ was only significant associated with worse cognitive HRQoL. Initial FT4 plasma, age at onset of therapy, initial T4 dose and motor skills were not significantly associated with HRQoL and self-worth.

Conclusions

Negative consequences in terms of HRQoL and self-worth are prevalent in children with CH, independent of disease factors, IQ and motor skills. Physicians should to be attentive to these consequences and provide attention and supportive care.     

A faculty trainer model: increasing knowledge and changing practice to improve perinatal HIV prevention and care

Although routine counseling and HIV testing of pregnant women is recommended, it is not yet universally offered. This paper reports on a project that trained health care providers from 2000 to 2002 using a faculty trainer (or train-the-trainer) model. The goals of the projects were to increase knowledge and change practice, increase HIV counseling and testing in prenatal care, and improve management of HIV in pregnant women. In four jurisdictions of the southeastern United States, 193 health care providers attended faculty trainer workshops using a standardized curriculum. Eighteen providers used the curriculum to train an additional 545 health care providers over 2 years. Participants in both faculty trainer workshops and trainerled seminars reported significant increases in perceived knowledge in all content areas and the intention to change clinical practice. The number of providers who became faculty trainers and then led seminars varied widely among the jurisdictions. Six-month follow-up of faculty trainers, although limited by a 63% response rate, found that over 90% of respondents reported the workshop had a positive impact on their care of women with and at risk for HIV. Our findings indicate the faculty trainer model is an effective way to educate practicing clinicians. Key elements to successful implementation were: ongoing support of faculty trainers by acquired immune deficiency syndrome (AIDS) educators, involvement of local HIV experts as trainers and resource persons, and use of a standardized curriculum based on national guidelines.     

Evaluation of RAD51C as cancer susceptibility gene in a large breast-ovarian cancer patient population referred for genetic testing

Despite extensive analysis of the BRCA1 and BRCA2 genes, germline mutations are detected in <20% of families with a presumed genetic predisposition for breast and ovarian cancer. Recent literature reported RAD51C as a new breast cancer susceptibility gene. In this study, we report the analysis of 410 patients from 351 unrelated pedigrees. All were referred for genetic testing and we selected families with at least one reported case of ovarian cancer in which BRCA1&2 mutations were previously ruled out. We analyzed the coding exons, intron-exons boundaries, and UTRs of RAD51C. Our mutation analysis did not reveal any unequivocal deleterious mutation. In total 12 unique sequence variations were identified of which two were novel. Our study and others suggest a low prevalence of RAD51C mutations with an exception for some founder populations. This observation is in favor of the rare allele hypothesis in the debate over the nature of the genetic contribution to individual susceptibility to breast and ovarian cancer and further genome-wide studies in high risk families are warranted.     

Personalized nanomedicine

Personalized medicine aims to individualize chemotherapeutic interventions on the basis of ex vivo and in vivo information on patient- and disease-specific characteristics. By noninvasively visualizing how well image-guided nanomedicines-that is, submicrometer-sized drug delivery systems containing both drugs and imaging agents within a single formulation, and designed to more specifically deliver drug molecules to pathologic sites-accumulate at the target site, patients likely to respond to nanomedicine-based therapeutic interventions may be preselected. In addition, by longitudinally monitoring how well patients respond to nanomedicine-based therapeutic interventions, drug doses and treatment protocols can be individualized and optimized during follow-up. Furthermore, noninvasive imaging information on the accumulation of nanomedicine formulations in potentially endangered healthy tissues may be used to exclude patients from further treatment. Consequently, combining noninvasive imaging with tumor-targeted drug delivery seems to hold significant potential for personalizing nanomedicine-based chemotherapeutic interventions, to achieve delivery of the right drug to the right location in the right patient at the right time. Clin Cancer Res; 18(18); 4889-94. ?2012 AACR.     

Endometrial cancer survival after breast cancer in relation to tamoxifen treatment: Pooled results from three countries

Introduction

Tamoxifen is an effective treatment for breast cancer but an undesirable side-effect is an increased risk of endometrial cancer, particularly rare tumor types associated with poor prognosis. We investigated whether tamoxifen therapy increases mortality among breast cancer patients subsequently diagnosed with endometrial cancer.

Methods

We pooled case-patient data from the three largest case-control studies of tamoxifen in relation to endometrial cancer after breast cancer (1,875 patients: Netherlands, 765; United Kingdom, 786; United States, 324) and collected follow-up information on vital status. Breast cancers were diagnosed in 1972 to 2005 with endometrial cancers diagnosed in 1978 to 2006. We used Cox proportional hazards survival analysis to estimate hazard ratios (HRs) and 95% confidence intervals (CI).

Results

A total of 1,104 deaths occurred during, on average, 5.8 years following endometrial cancer (32% attributed to breast cancer, 25% to endometrial cancer). Mortality from endometrial cancer increased significantly with unfavorable non-endometrioid morphologies (P < 0.0001), International Federation of Gynaecology and Obstetrics staging system for gynecological malignancy (FIGO) stage (P < 0.0001) and age (P < 0.0001). No overall association was observed between tamoxifen treatment and endometrial cancer mortality (HR = 1.17 (95% CI: (0.89 to 1.55)). Tamoxifen use for at least five years was associated with increased endometrial cancer mortality (HR = 1.59 (1.13 to 2.25)). This association appeared to be due primarily to the excess of unfavorable histologies and advanced stage in women using tamoxifen for five or more years since the association with mortality was no longer significant after adjustment for morphological type and FIGO stage (HR = 1.37 (0.97 to 1.93)). Those patients with endometrioid tumors, who stopped tamoxifen use at least five years before their endometrial cancer diagnosis, had a greater mortality risk from endometrial cancer than endometrioid patients with no tamoxifen exposure (HR = 2.11 (1.13 to 3.94)). The explanation for this latter observation is not apparent.

Conclusions

Patients with endometrial cancer after breast cancer who received tamoxifen treatment for five years for breast cancer have greater endometrial cancer mortality risk than those who did not receive tamoxifen. This can be attributed to non-endometrioid histological subtypes with poorer prognosis among long term tamoxifen users.     

Requirements for cellular co-trafficking of factor VIII and von Willebrand factor to Weibel-Palade bodies.

BACKGROUND: von Willebrand factor (VWF) serves a critical role as a carrier of factor (F)VIII in circulation. While it is generally believed that FVIII and VWF assemble in circulation after secretion from different cells, an alternative view is that cells should exist that co-express FVIII and VWF. OBJECTIVES: In this study, intracellular co-expression of FVIII and VWF was studied, with particular reference to complex assembly and high-affinity interaction. METHODS: Using yellow fluorescent protein-tagged FVIII (FVIII-YFP) and cyan fluorescent protein-tagged VWF (VWF-CFP), we studied intracellular trafficking in human embryonic kidney (HEK293) cells and human umbilical vein endothelial cells (HUVEC). The role of the high-affinity interaction between FVIII and VWF was assessed using a FVIII-YFP variant carrying a Tyr1680Phe substitution, which abolishes high-affinity binding to VWF. Cellular trafficking studies were complemented by binding studies employing purified proteins. RESULTS: Solid phase binding assays employing FVIII-YFP demonstrated that the presence of the fluorescent moiety did not compromise high-affinity binding (K(d) = 0.065 +/- 0.008 nm) whereas the binding of the Tyr1680Phe FVIII-YFP variant was significantly reduced. Co-expression studies in HEK293 cells revealed intracellular co-storage of both FVIII-YFP and Tyr1680Phe FVIII-YFP within VWF-containing storage organelles. In addition, expression of FVIII-YFP and Tyr1680Phe FVIII-YFP in HUVEC demonstrated co-trafficking with endogenous VWF to authentic Weibel-Palade bodies (WPBs). CONCLUSIONS: Our findings demonstrate that FVIII trafficking to WPBs is independent of Tyr1680 and high-affinity binding to VWF. We therefore conclude that the structural requirements that determine intracellular co-trafficking differ from those that determine complex assembly in circulation.     

Chromium and zinc concentrations in pediatric patients receiving long-term parenteral nutrition.

Serum, urine, and parenteral nutrition (PN) chromium and zinc concentrations in pediatric patients receiving long-term PN were studied. Serum, urine, and PN chromium and zinc concentrations were measured at baseline and four to six months later in four infants (less than 1 year old) and seven children (1-12 years old) receiving long-term PN. In the children, serum, urine, and PN solution zinc concentrations were measured monthly after the amino acid product was changed from a standard to a pediatric product with monthly dosages of 0, 20, 30, and 40 mg of cysteine hydrochloride per gram of amino acids. The mean +/- S.D. baseline serum chromium concentration was 4.9+/-1.9 microg/L (normal value, <0.3 microg/L); the urine chromium concentration ranged from 3.4 to 32.2 microg/L. The mean +/- S.D. prescribed chromium dosage was 0.18+/-0.05 microg/kg/day, and the dosage delivered in PN solutions was 0.41+/-0.23 microg/ kg/day. At baseline, the mean +/- S.D. serum zinc concentration was 1383+/-472 microg/L (normal range, 430 to 940 microg/L), and the prescribed and delivered zinc dosages were 177+/-10 and 238+/-145 microg/kg/ day, respectively. With 20, 30, and 40 mg of cysteine per gram of amino acids, the mean +/- S.D. serum zinc concentration was 1728+/-782, 1664+/-349, and 1685+/-268 microg/L, respectively, and the actual zinc dosages delivered were 209+/-10, 270+/-148, and 322+/-194 microg/kg/day, respectively. Serum and urine chromium concentrations were abnormally high in infants and children receiving PN solutions supplemented with normal doses of these trace elements; an escalating dosage of cysteine in the children tended to increase serum and urine zinc concentrations.