Divergence of structural strategies for homophilic E-cadherin binding among bilaterians

Homophilic binding of E-cadherins through their ectodomains is fundamental to epithelial cell-cell adhesion. Despite this, E-cadherin ectodomains have evolved differently in the vertebrate and insect lineages. Of the five rod-like, tandemly aligned extracellular cadherin domains of vertebrate E-cadherin, the tip extracellular cadherin domain plays a pivotal role in binding interactions. Comparatively, the six consecutive N-terminal extracellular cadherin domains of Drosophila E-cadherin, DE-cadherin (also known as Shotgun), can mediate adhesion; however, the underlying mechanism is unknown. Here, we report atomic force microscopy imaging of DE-cadherin extracellular cadherin domains. We identified a tightly folded globular structure formed by the four N-terminal-most extracellular cadherin domains stabilized by the subsequent two extracellular cadherin domains. Analysis of hybrid cadherins from different insects indicated that the E-cadherin globular portion is associated with determining homophilic binding specificity. The second to fourth extracellular cadherin domains were identified as the minimal portion capable of mediating exclusive homophilic binding specificity. Our findings suggest that the N-terminal-most four extracellular cadherin domains of insect E-cadherin are functionally comparable with the N-terminal-most single extracellular cadherin domain of vertebrate E-cadherin, but that their mechanisms might significantly differ. This work illuminates the divergence of structural strategies for E-cadherin homophilic binding among bilaterians.

Properties of the feline tumour suppressor reduced expression in immortalized cells (REIC/Dkk-3)

Reduced expression in immortalized cells (REIC/Dkk-3), a member of the human Dickkopf (Dkk) family, is a growth suppressor in human and canine mammary tumours. Mammary gland tumours are common neoplasms with high malignancy in female cats. The purpose of this study was to clone the feline REIC/Dkk-3 homolog, investigate its expression in cell lines established from feline mammary gland tumours, and test its tumour suppressor function. Western blot analysis revealed that expression of the REIC/Dkk-3 protein was reduced in feline mammary carcinoma cell lines. Forced expression of REIC/Dkk-3 induced apoptosis in feline mammary tumour cell lines. These results demonstrate that REIC/Dkk-3 expression, which is downregulated in feline mammary tumour cell lines, results in the induction of apoptosis in these cells. Our findings suggest that feline REIC/Dkk-3 represents a potential molecular target for the development of therapies against feline mammary cancers.

Abstract P4-13-21: A pilot study of pertuzumab, trastuzumab and eribulin for patients with advanced HER2 positive breast cancer

[Introduction] The triple therapy of pertuzumab, trastuzumab and taxanes (docetaxel or paclitaxel) is coming into widespread use, because of the beneficial effects on HER2 positive breast cancer. However, we don't have enough information about the efficacy and safety of other agents with trastuzumab and pertuzumab (TP). We studied triple therapy of pertuzumab, trastuzumab and eribulin (PTE) for advanced HER2 positive breast cancer to assess the efficacy, safety and QOL prospectively (UMIN000012018).

[Patients and methods] Responses were assessed by RECIST criteria v1.1. Adverse events (AEs) were graded according to CTCAE v4.0. Patients with advanced HER2 positive breast cancer were treated with pertuzumab (840 mg loading then 420 mg, day 1), trastuzumab (8 mg/kg loading then 6 mg/kg, day 1), and eribulin (1.4 mg/m2, day 1 and 8) every 3 weeks. Dose reduction was allowed when patients developed febrile neutropenia, grade 3-5 non-hematologic toxicity or skipped day 8 eribulin administration because of neutrophil count <1000/mm3. QOL was assessed using FACT-B at baseline and 3 months after initial treatment.

[Results] Ten patients were enrolled. Median age of patients was 60 years-old (35-75). Median number of prior chemoregimen for metastatic disease was 3 (0-5). Two patients had a history of docetaxel allergy. Median number of PTE cycle was 6 (3-12). Eight patients reduced eribulin doses 1.4 mg/m2 to 1.1 mg/m2 because of AEs (2 patients), skipped day 8 eribulin (4 patients), or physician's choice (2 patients). One complete response, 1 partial response and 5 stable disease were achieved at 3 months. Two patients (1 CR and 1 SD) stopped eribulin and received TP as maintenance therapy. At 3 months, all 3 patients with progressive disease developed brain metastasis. Two patients had extracranial progressive lesions, but 1 patient had partial response for extracranial disease.

The common treatment-related AEs were leukopenia, neutropenia, lymphopenia diarrhea, hypokalemia and stomatitis. Grade 3 AEs were leukopenia (7 patients), neutropenia (8 patients), lymphopenia (2 patients), febrile neutropenia (1 patient), hypokalemia (1 patient) and peripheral neuropathy (1 patient). Grade 4/5 AEs were not observed.

Nine patients could be assessed QOL. FACT-B TOI, FACT-G and FACT-B total score had a tendency to be improved at 3 months.

[Conclusion] The PTE therapy showed appropriate clinical effect for extracranial lesions and maintained QOL of patients with advanced HER2 positive breast cancer. It may be a choice for patients who have taxane-resistant diseases or a history of taxane allergy.

Many patients needed to reduce eribulin dosage. When the PTE therapy is referred to advanced HER2 positive breast cancer patients as a palliative chemotherapy, eribulin (1.1mg/m2) might be a reasonable dosage.

Citation Format: Ishihara M, Tamaru S, Oda H, Yamashita Y, Tono Y, Mizuno T, Katayama N. A pilot study of pertuzumab, trastuzumab and eribulin for patients with advanced HER2 positive breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-13-21.

Bridging a 30 mm defect in the canine ulnar nerve using vessel-containing conduits with implantation of bone marrow stromal cells

Previously, we showed that undifferentiated bone marrow stromal cell (uBMSC) implantation and vessel insertion into a nerve conduit facilitated peripheral nerve regeneration in a rodent model. In this study, we investigated the efficacy of the uBMSC-laden vessel-containing conduit in repair of segmental nerve defects, using a canine model. Eight beagle dogs were used in this study. Thirty-millimeter ulnar nerve defects were repaired with the conduits (right forelimbs, n = 8) or autografts (left forelimbs, n = 7). In the conduit group, the ulnar artery was inserted into the l-lactide/ε-caprolactone tube, which was filled with autologous uBMSCs obtained from the ilium. In the autograft group, the reversed nerve segments were sutured in situ. At 8 weeks, one dog with only nerve repair with the conduit was sacrificed and the regenerated nerve in the conduit underwent immunohistochemistry for investigation of the differentiation capability of the implanted uBMSCs. In the remaining seven dogs, the repaired nerves underwent electrophysiological examination at 12 and 24 weeks and morphometric measurements at 24 weeks. The wet weight of hypothenar muscles was measured at 24 weeks. At 8 weeks, almost 35% of the implanted uBMSCs expressed glial markers. At 12 weeks, amplitude (0.4 ± 0.4mV) and conduction velocity (18.9 ± 14.3m/s) were significantly lower in the conduit group than in the autograft group (3.2 ± 2.5 mV, 34.9 ± 12.1 m/s, P < 0.05). Although the nerve regeneration in the conduit group was inferior when compared with the autograft group at 24 weeks, there were no significant differences between both groups, regarding amplitude (10.9 ± 7.3 vs. 25.3 ± 20.1 mV; P = 0.11), conduction velocity (23.5 ± 8.7 vs 31.6 ± 20.0m/s; P = 0.35), myelinated axon number (7032 ± 4188 vs 7165 ± 1814; P = 0.94), diameter (1.73 ± 0.31 vs 2.09 ± 0.39μm; P = 0.09), or muscle weight (1.02 ± 0.40 vs 1.19 ± 0.26g; P = 0.36). In conclusion, this study showed that vessel-containing tubes with uBMSC implantation may be an option for treatment of peripheral nerve injuries. However, further investigations are needed. © 2015 Wiley Periodicals, Inc. Microsurgery 36:316-324, 2016.

Osteoporosis therapy: a novel insight from natural homeostatic system in the skeleton

The skeleton normally responds to mechanical environment to maintain the resulting elastic deformation (strain) of bone, while increased bone strength by an osteoporosis drug results in decreased bone strain. Thus, it can be hypothesized that the effect of osteoporosis therapy is limited by natural homeostatic system in the skeleton. This logic is consistent with the fact that there exists a powerful effect that returns bone mass to its pre-treatment level after the withdrawal of treatment with osteoporosis agents. The present hypothesis provides a new significant insight into the mechanisms by which osteoporosis drugs improve bone fragility. Here we briefly discuss the effects of teriparatide, romosozumab, and odanacatib on bones in animals and humans.

The osteoclast: a potential therapeutic target of bone and joint destruction in rheumatoid arthritis

Abstract There is accumulating evidence that osteoclasts, the primary cells responsible for bone resorption, are involved in bone and joint destruction in rheumatoid arthritis (RA). Recent progress in bone cell biology has revealed the molecular mechanism of osteoclast differentiation and bone resorption by mature osteoclasts. We here highlight the potential role of RANKL-RANK pathways in bone destruction in RA. We also describe our recent trials on gene therapy of arthritic joint disease targeting osteoclasts by regulating Src kinase activity in the cells.