Recently we reported that the ATP-binding cassette transporter Abcc10, also known as multidrug resistance protein 7 (Mrp7), is able to confer resistance to a variety of anticancer agents including taxanes. However, the in vivo functions of the pump have not been determined to any extent. Here we generated and analyzed Abcc10−/− mice in order to investigate the ability of Abcc10 to function as an endogenous resistance factor. Mouse embryo fibroblasts derived from Abcc10 −/− mice were hypersensitive to docetaxel, paclitaxel, vincristine and Ara-C and exhibited increased cellular drug accumulation, relative to wild type controls. Abcc10 null mice treated with paclitaxel exhibited increased lethality associated with neutropenia and marked bone marrow toxicity. Toxicity in spleen and thymus was also evident. These findings indicate that Abcc10 is dispensable for health and viability, and that it is an endogenous resistance factor for taxanes, other natural product agents and nucleoside analogs. This is the first demonstration that an ATP-binding cassette transporter other than P-glycoprotein can affect in vivo tissue sensitivity towards taxanes.

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Endothelial cell interactions with normal and cancerous breast epithelial cells have been widely studied in tissue growth and development, as well as in angiogenesis and metastasis. Despite the understanding that 3D multicellular architecture is critical to the cell phenotype, 3D vascular structures have not yet been cocultured with 3D breast spheroids in vitro. The objective of this study was therefore to create a hierarchical, multiscale model of vascular endothelial-breast epithelial cell interactions in which both cell types were assembled into their 3D architectures. The model was successfully fabricated by adding preformed breast spheroids onto preformed endothelial tube-like networks. Through this model, we observed that breast spheroids maintain vascular tube-like networks. Over time, breast epithelial cells migrate out of the spheroid structure along the endothelial networks. This research shows that 3D cell structures serve as an important building block for creating multicellular coculture models to study physiologically relevant cell−cell interactions.

This paper details the systematic approach used to develop a viable clinical prototype of a therapeutic ultrasound applicator and discusses the rationale and deliberations that led to the design strategy. The applicator was specifically devised to treat chronic wounds and - to the best of the author's knowledge - is the first truly wearable device with a proven record of reducing healing time, directly translating to a reduction of healthcare costs. The prototype operates in the kHz (20-100) range of frequencies and uses non-cavitational and non-thermal levels of ultrasound energy. Hence, in the absence of inertial cavitation and temperature elevation, the tissue-ultrasound interaction is considered to be dependent on stable cavitation (if any) and radiation force. The peak acoustic output pressure amplitude is limited to 55 kPa, corresponding to a spatial peak temporal peak intensity of 100 mW/cm2. This level of intensity is considered to be safe to apply for extended (up to four hours) periods of time. The patch-like applicator design is suitable to be embedded in wound dressing. With its light weight (<20g) and circular (40 mm dia) disk shape architecture, the applicator is well suited for chronic wound treatment. A small (n=8) pilot study on the effects of the applicator on diabetic ulcers healing time is presented. The average time to wound closure was 4.7 weeks for subjects treated with the active ultrasound applicator, compared to 12 weeks for subjects treated with a sham applicator, suggesting that patients with diabetic ulcers may benefit from the proposed treatment.

Low-frequency, low-intensity ultrasound has been previously shown to promote healing of chronic wounds in humans, but mechanisms behind these effects are poorly understood. The purpose of this study was to evaluate gene expression differences in debrided human venous ulcer tissue from patients treated with low-frequency (20 kHz), low-intensity (100 mW/cm2) ultrasound compared to a sham treatment in an effort to better understand the potential biological mechanisms. Debrided venous ulcer tissue was collected from 32 subjects one week after sham treatment or low-frequency, low-intensity ultrasound treatment. Of these samples, 7 samples (3 ultrasound treated and 4 sham treated) yielded sufficient quality total RNA for analysis by ultra-high multiplexed PCR (Ampliseq) and expression of more than 24,000 genes was analyzed. 477 genes were found to be significantly different between the ultrasound and sham groups using cut-off values of p<0.05 and fold change of 2. Gene set enrichment analysis identified 20 significantly enriched gene sets from upregulated genes and 4 significantly enriched gene sets from downregulated genes. Most of the enriched gene sets from upregulated genes were related to cell-cell signaling pathways. The most significantly enriched gene set from downregulated genes was the inflammatory response gene set. These findings show that therapeutic ultrasound influences cellular behavior in chronic wounds as early as one week after application. Considering the well-known role of chronic inflammation in impairing wound healing in chronic wounds, these results suggest that a downregulation of inflammatory genes is a possible biological mechanism of ultrasound-mediated venous chronic wound healing. Such increased understanding may ultimately lead to the enhancement of ultrasound devices to accelerate chronic wound healing and increase patient quality of life.

Supplementary Figure Legend from Contribution of Abcc10 (Mrp7) to <i>In Vivo</i> Paclitaxel Resistance as Assessed in <i>Abcc10^−/−</i> Mice

Supplementary Table 1 from Contribution of Abcc10 (Mrp7) to <i>In Vivo</i> Paclitaxel Resistance as Assessed in <i>Abcc10^−/−</i> Mice

Supplementary Figure Legend from Contribution of Abcc10 (Mrp7) to <i>In Vivo</i> Paclitaxel Resistance as Assessed in <i>Abcc10^−/−</i> Mice