Receptor clustering and activation by multivalent interaction through recognition peptides presented on exosomes

We demonstrate a novel system for inducing clustering of cell surface receptors via recognition peptide segments displayed on exosomes, leading to receptor activation. With this system, targeting of receptor-expressing cells and facilitation of the endocytic uptake of exosomes, which contained the anti-cancer protein saporin, were successfully achieved, leading to cell death.

Novel Mechanisms of Resistance to Investigational Molecularly Targeted Drugs

Drug resistance is a critical problem inhibiting the effective use of targeted molecular cancer therapies. Investigators have revealed a variety of resistance mechanisms, including alterations in drug targets, activation of pro-survival pathways, and the ineffective induction of cell death. The key alterations driving this resistance are likely condition-dependent, and a detailed analysis would be required to characterize these diverse alterations under a variety of conditions in order to facilitate practical precision medicine for treating individual cancer patients. We have been investigating the molecular mechanisms of anti-cancer drug resistance, and analyzed our original resistant cells against anti-mitotic kinase inhibitors. This study suggests that novel mechanisms reduce cytokinetic dysregulation caused by those inhibitors, and anti-apoptotic activities are associated with resistant phenotypes. These observations suggest that the activation of various bypass mechanisms may allow cancer cells to avoid the selective antiproliferative effect of molecularly targeted drugs, and such bypass activation mechanism would thus be a critical target for designing combination chemotherapy to overcome non-genetic drug resistance.

Assessing the progression of chronic periodontitis using subgingival pathogen levels: a 24-month prospective multicenter cohort study

BACKGROUND

The diagnosis of the progression of periodontitis presently depends on the use of clinical symptoms (such as attachment loss) and radiographic imaging. The aim of the multicenter study described here was to evaluate the diagnostic use of the bacterial content of subgingival plaque recovered from the deepest pockets in assessing disease progression in chronic periodontitis patients.

METHODS

This study consisted of a 24-month investigation of a total of 163 patients with chronic periodontitis who received trimonthly follow-up care. Subgingival plaque from the deepest pockets was recovered and assessed for bacterial content of Porphyromonas gingivalis, Prevotella intermedia, and Aggregatibacter actinomycetemcomitans using the modified Invader PLUS assay. The corresponding serum IgG titers were measured using ELISA. Changes in clinical parameters were evaluated over the course of 24 months. The sensitivity, specificity, and prediction values were calculated and used to determine cutoff points for prediction of the progression of chronic periodontitis.

RESULTS

Of the 124 individuals who completed the 24-month monitoring phase, 62 exhibited progression of periodontitis, whereas 62 demonstrated stable disease. The P. gingivalis counts of subgingival plaque from the deepest pockets was significantly associated with the progression of periodontitis (p < 0.001, positive predictive value = 0.708).

CONCLUSIONS

The P. gingivalis counts of subgingival plaque from the deepest pockets may be associated with the progression of periodontitis.

Functional Effects of AKT3 on Aurora Kinase Inhibitor-induced Aneuploidy

The suppression of mitotic Aurora kinases (AURKs) by AURK inhibitors frequently causes cytokinetic failure, leading to polyploidy or aneuploidy, indicating the critical role of AURK-mediated phosphorylation during cytokinesis. We demonstrate the deregulated expression of AKT3 in Aurora kinase inhibitor (AURKi)-resistant cells, which we established from human colorectal cancer HCT 116 cells. The AKT family, which includes AKT1, -2, and -3, plays multiple roles in antiapoptotic functions and drug resistance and is involved in cell growth and survival pathways. We found that an AKT inhibitor, AZD5363, showed synergistic effect with an AURKi, VX-680, on two AKT3-expressing AURKi-resistant cell lines, and AKT3 knockdown sensitized cells to VX-680. Consistent with these activities, AKT3 expression suppressed AURKi-induced apoptosis and conferred resistance to AURKi. Thus, AKT3 expression affects cell sensitivity to AURKi. Moreover, we found that AKT3 expression suppressed AURKi-induced aneuploidy, and inversely AKT3 knockdown enhanced it. In addition, partial co-localization of AKT3 with AURKB was observed during anaphase. Overall, this study suggests that AKT3 could repress the antiproliferative effects of AURKi, with a novel activity particularly suppressing the aneuploidy induction.

PGE2 Activates Cementoclastogenesis by Cementoblasts via EP4

Destruction of cementum and alveolar bone is the main causative event for the exfoliation of teeth as a consequence of periodontitis. Prostaglandin E2 (PGE2) and PGE receptor subtypes (EPs) play an important role in modulating osteoblast-mediated osteoclastogenesis; however, no information is available on the role of PGE2 and EPs in regulating cementoblast-mediated cementoclastogenesis. We hypothesized that the PGE2-EPs pathway also regulates cementoblasts’ ability to activate cementoclasts. For these studies, OCCM-30 cells (a mouse cementoblast cell line) were exposed to PGE2 and specific EP agonists. PGE2 (100 ng/mL) and EP4 agonist (1 μM) up-regulated RANKL and IL-6 mRNA levels, while they down-regulated OPG mRNA expression. The EP4 antagonist (1 μM) eliminated these effects of PGE2. PGE2 treatment of co-cultures of OCCM-30 cells with bone marrow cells induced TRAP-positive cells via the EP4 pathway. These findings suggest that PGE2 promotes cementoblast-mediated cementoclastogenesis by regulating the expression of RANKL and OPG via the EP4 pathway.

Effect of AKT3 expression on MYC- and caspase-8-dependent apoptosis caused by polo-like kinase inhibitors in HCT 116 cells

Polo-like kinase (PLK) is a cell-cycle regulator that is overexpressed in several cancer cell types. Polo-like kinase is considered a novel target for cancer therapies, and several PLK inhibitors (PLKis), including BI 2536, BI 6727, and GSK461364, have been developed. In this study, we established five BI 2536-resistant cell lines from human colorectal cancer HCT 116 cells, to explore the resistance mechanism and identify predictable biomarkers of PLKis. We showed that PLKi-induced caspase-8 activation was attenuated in the BI 2536-resistant cell lines. We also showed that the expression of P-glycoprotein (P-GP) and AKT3 was upregulated, whereas that of MYC was downregulated in some BI 2536-resistant cell lines. Expression of P-GP conferred resistance to PLKis, and PLKi-induced apoptosis was dependent on MYC and caspase-8 in HCT 116 cells. We also showed for the first time that AKT3 suppressed BI 6727-induced caspase-8 activation and conferred resistance to PLKis. Collectively, these results indicate that MYC, caspase-8, P-GP, and AKT3 play critical roles in PLKi-induced apoptosis. Therefore, they are candidate biomarkers of the pharmacological efficacy of PLKis.

RSK1 protects P-glycoprotein/ABCB1 against ubiquitin-proteasomal degradation by downregulating the ubiquitin-conjugating enzyme E2 R1

P-glycoprotein (P-gp) is a critical determinant of multidrug resistance in cancer. We previously reported that MAPK inhibition downregulates P-gp expression and that P-gp undergoes ubiquitin-proteasomal degradation regulated by UBE2R1 and SCF^Fbx15. Here, we investigated the crosstalk between MAPK inhibition and the ubiquitin-proteasomal degradation of P-gp. Proteasome inhibitors or knockdown of FBXO15 and/or UBE2R1 cancelled MEK inhibitor-induced P-gp downregulation. RSK1 phosphorylated Thr162 on UBE2R1 but did not phosphorylate FBXO15. MEK and RSK inhibitors increased UBE2R1-WT but not UBE2R1-T162D and -T162A expression. UBE2R1-T162D showed higher self-ubiquitination and destabilisation than UBE2R1-WT and -T162A. Unlike UBE2R1-WT and -T162A, UBE2R1-T162D did not induce P-gp ubiquitination. UBE2R1-WT or -T162A downregulated P-gp expression and upregulated rhodamine 123 level and sensitivity to vincristine and doxorubicin. However, UBE2R1-T162D did not confer any change in P-gp expression, rhodamine 123 accumulation and sensitivity to the drugs. These results suggest that RSK1 protects P-gp against ubiquitination by reducing UBE2R1 stability.

Inducement of tissue regeneration of harvested hamstring tendons in a rabbit model

OBJECTIVES

The objective of this study was to determine if the use of fascia lata as a tendon regeneration guide (placed into the tendon canal following harvesting the semitendinosus tendon) would improve the incidence of tissue regeneration and prevent fatty degeneration of the semitendinosus muscle.

MATERIALS AND METHODS

Bilateral semitendinosus tendons were harvested from rabbits using a tendon stripper. On the inducing graft (IG) side, the tendon canal and semitendinosus tibial attachment site were connected by the fascia lata, which was harvested at the same width as the semitendinosus tendon. On the control side, no special procedures were performed. Two groups of six rabbits were killed at post-operative weeks 4 and 8, respectively. In addition, three healthy rabbits were killed to obtain normal tissue. We evaluated the incidence of tendon tissue regeneration, cross-sectional area of the regenerated tendon tissue and proportion of fatty tissue in the semitendinosus muscle.

RESULTS

At post-operative week 8, the distal end of the regenerated tissue reached the vicinity of the tibial insertion on the control side in two of six specimens. On the IG side, the regenerated tissue maintained continuity with the tibial insertion in all specimens. The cross-sectional area of the IG side was significantly greater than that of the control side. The proportion of fatty tissue in the semitendinosus muscle on the IG side was comparable with that of the control side, but was significantly greater than that of the normal muscle.

CONCLUSIONS

Tendon tissue regenerated with the fascia lata graft was thicker than naturally occurring regenerated tissue. However, the proportion of fatty tissue in the semitendinosus muscle was greater than that of normal muscle.Cite this article: K. Tabuchi, T. Soejima, H. Murakami, K. Noguchi, N. Shiba, K. Nagata. Inducement of tissue regeneration of harvested hamstring tendons in a rabbit model. Bone Joint Res 2016;5:247-252. DOI: 10.1302/2046-3758.56.2000585.

Salivary pathogen and serum antibody to assess the progression of chronic periodontitis: a 24-mo prospective multicenter cohort study

BACKGROUND AND OBJECTIVE

A diagnosis of periodontitis progression is presently limited to clinical parameters such as attachment loss and radiographic imaging. The aim of this multicenter study was to monitor disease progression in patients with chronic periodontitis during a 24-mo follow-up program and to evaluate the amount of bacteria in saliva and corresponding IgG titers in serum for determining the diagnostic usefulness of each in indicating disease progression and stability.

MATERIAL AND METHODS

A total of 163 patients with chronic periodontitis who received trimonthly follow-up care were observed for 24 mo. The clinical parameters and salivary content of Porphyromonas gingivalis, Prevotella intermedia and Aggregatibacter actinomycetemcomitans were assessed using the modified Invader PLUS assay, and the corresponding serum IgG titers were measured using ELISA. The changes through 24 mo were analyzed using cut-off values calculated for each factor. One-way ANOVA or Fisher's exact test was used to perform between-group comparison for the data collected. Diagnostic values were calculated using Fisher's exact test.

RESULTS

Of the 124 individuals who completed the 24-mo monitoring phase, 62 exhibited periodontitis progression, whereas 62 demonstrated stable disease. Seven patients withdrew because of acute periodontal abscess. The ratio of P. gingivalis to total bacteria and the combination of P. gingivalis counts and IgG titers against P. gingivalis were significantly related to the progression of periodontitis. The combination of P. gingivalis ratio and P. gingivalis IgG titers was significantly associated with the progression of periodontitis (p = 0.001, sensitivity = 0.339, specificity = 0.790).

CONCLUSIONS

It is suggested that the combination of P. gingivalis ratio in saliva and serum IgG titers against P. gingivalis may be associated with the progression of periodontitis.

Upregulation of cellular glutathione levels in human ABCB5- and murine Abcb5-transfected cells

Background

Previously, we have demonstrated that human ABCB5 is a full-sized ATP-binding cassette transporter that shares strong homology with ABCB1/P-glycoprotein. ABCB5-transfected cells showed resistance to taxanes and anthracyclines. Herein, we further screened ABCB5 substrates, and explored the mechanism of resistance.

Methods

Sensitivity of the cells to test compounds was evaluated using cell growth inhibition assay. Cellular levels of buthionine sulfoximine (BSO), glutathione and amino acids were measured using HPLC and an enzyme-based assay. Cellular and vesicular transport of glutathione was evaluated by a radiolabeled substrate. Expression levels of glutathione-metabolizing enzymes were assessed by RT-PCR.

Results

Human ABCB5-transfected 293/B5-11 cells and murine Abcb5-transfected 293/mb5-8 cells showed 6.5- and 14-fold higher resistance to BSO than the mock-transfected 293/mock cells, respectively. BSO is an inhibitor of gamma-glutamylcysteine ligase (GCL), which is a key enzyme of glutathione synthesis. 293/B5-11 and 293/mb5-8 cells also showed resistance to methionine sulfoximine, another GCL inhibitor. A cellular uptake experiment revealed that BSO accumulation in 293/B5-11 and 293/mb5-8 cells was similar to that in 293/mock cells, suggesting that BSO is not an ABCB5 substrate. The cellular glutathione content in 293/B5-11 and 293/mb5-8 cells was significantly higher than that in 293/mock cells. Evaluation of the BSO effect on the cellular glutathione content showed that compared with 293/mock cells the BSO concentration required for a 50 % reduction in glutathione content in 293/B5-11 and 293/mb5-8 cells was approximately 2- to 3-fold higher. This result suggests that the BSO resistance of the ABCB5- and Abcb5-transfected cells can be attributed to the reduced effect of BSO on the transfectants. Cellular and vesicular transport assays showed that the transport of radiolabeled glutathione in 293/B5-11 cells was similar to that in 293/mock cells. The mRNA expression of genes encoding glutathione-metabolizing enzymes in 293/B5-11 cells was similar to that in 293/mock cells. The cellular content of Glu, a precursor of glutathione, in 293/B5-11 and 293/mb5-8 cells was higher than that in 293/mock cells.

Conclusions

ABCB5/Abcb5-transfected cells showed resistance to BSO, which is not a substrate of ABCB5. Our results suggest that ABCB5/Abcb5 upregulates cellular glutathione levels to protect cells from various poisons.

Abstract B62: AKT3 expression modulates chemosensitivity to aurora kinase inhibitors

The aurora kinases in human consist of three members, Aurora A, B and C (AURKA, B and C). They are involved in cell cycle progression, especially in mitosis, and aberrant expressions of them are reported in many cancer tissue types. Therefore, AURKs would serve as useful molecular targets for anti-cancer agents and many investigational drugs are currently under development. To understand pharmacological determinants affecting the chemosensitivity to aurora kinase inhibitors, we have established five resistant cell lines to an aurora kinase inhibitor VX 680 by treating human colon cancer HCT 116 cells in vitro with increasing concentrations of VX 680 (40∼200 nmol/L) over a period of 6 months. These VX 680-resistant clones showed aneuploidy and cross-resistance to other aurora kinase inhibitors AZD1152-HQPA and MLN8237. Regarding drug resistance-associated molecules, P-gp and BCRP overexpression were not common to the VX 680-resistant clones, despite the fact that overexpression of P-gp and BCRP conferred strong resistance to VX 680 and AZD1152-HQPA. Gene expression analysis by cDNA microarray indicated that Akt3 was up-regulated in the VX 680-resistant cells. Transient overexpression of myristylated-Akt3 in Hela cells repressed AZD1152-HQPA-induced cell death and polyploidy induction, and stable expression of myristylated-Akt3 in HCT 116 cells induced resistance to both VX 680 and AZD1152-HQPA. In addition, confocal microscopic study showed that endogenous AKT3 was detected during mitosis. These observations suggest that AKT3 activity can affect the mechanism for the chemosensitivity to aurora kinase inhibitors.

Citation Format: Kohji Noguchi, Kazuhiro Katayama, Yoshikazu Sugimoto. AKT3 expression modulates chemosensitivity to aurora kinase inhibitors. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr B62.

Healing of localized gingival recessions treated with a coronally advanced flap alone or combined with an enamel matrix derivative and a porcine acellular dermal matrix: a preclinical study

OBJECTIVE

This study aimed to evaluate the effects of a porcine acellular dermal matrix (PADM) with or without an enamel matrix derivative (EMD) on gingival recession defects treated with a coronally advanced flap (CAF) in dogs.

MATERIALS AND METHODS

Miller class II gingival recession defects (5 mm wide and 7 mm deep) were surgically created on the labial side of bilateral maxillary canines in 12 dogs. After 8 weeks of plaque accumulation, the 24 chronic defects were randomly assigned to one of the following 4 treatments: CAF, CAF with PADM (CAF/PADM), CAF with EMD (CAF/EMD), and CAF with EMD and PADM (CAF/EMD/PADM). The animals were sacrificed 10 weeks after surgery for histologic evaluation.

RESULTS

In all groups, root coverage was obtained to a varying degree. PADM was well incorporated in gingival connective tissue in the CAF/PADM and in the CAF/EMD/PADM groups. The height of newly formed bone was significantly greater in the CAF/EMD/PADM group than in the CAF and CAF/PADM groups. New cementum with periodontal ligament-like tissue was predominantly found in the CAF/EMD and CAF/EMD/PADM groups. The CAF/EMD/PADM group showed the greatest amount of new cementum among the groups examined, although the difference was not statistically significant.

CONCLUSION

Within the limitations of the present study, it can be concluded that CAF/EMD/PADM treatment may promote periodontal regeneration in gingival recession defects.

CLINICAL RELEVANCE

The present results suggest that the combination of EMD and PADM in conjunction with CAF may represent a promising approach for treating single Miller class II gingival recessions.

A potential anti-allodynic mechanism of GDNF following L5 spinal nerve ligation; Mitigation of NPY up-regulation in the touch sense pathway

Intrathecal delivery of glial cell line-derived neurotrophic factor (GDNF) reverses mechanical allodynia after 5th lumbar (L5) spinal nerve ligation (SNL). However, the molecular mechanism behind this process is not fully understood. Following sciatic nerve injury, primary afferent neurons in the injured dorsal root ganglion (DRG) begin to express neuropeptide Y (NPY) that is absent in normal DRG. The aim of the current study was to determine the relationship of this de novo expression of NPY and the anti-allodynic effect of GDNF. Following L5 SNL, 73% of neurons began to express NPY mRNA in the ipsilateral L5 DRG and robust NPY-immunoreactive fibers appeared in the ipsilateral GN where the touch-sense mediating A-fiber primary afferents from the hindpaw terminate. Seven-daylong intrathecal infusion of GDNF at the L5 DRG level, starting on day three when mechanical allodynia had fully developed, reversed once-established these changes. The GN neurons normally expressed NPY Y1 receptor, but not Y2, Y4, or Y5 receptors, and L5 SNL did not change the expression pattern. Bolus intracisternal injection of BIBP3226, a Y1 receptor antagonist, dose-dependently reversed mechanical allodynia. We demonstrated that GDNF reversed once-established mechanical allodynia as well as NPY induction in the touch-sense processing pathway. NPY could facilitate touch-sense processing by Y1 receptor in the gracile nucleus after peripheral nerve injury. GDNF may exert anti-allodynic effects through mitigation of this NPY up-regulation. The effectiveness of delayed treatment further indicates the therapeutic potential of GDNF on neuropathic pain.

De novo expression of Nav1.7 in injured putative proprioceptive afferents: Multiple tetrodotoxin-sensitive sodium channels are retained in the rat dorsal root after spinal nerve ligation

Tetrodotoxin-sensitive (TTX-s) spontaneous activity is recorded from the dorsal roots after peripheral nerve injury. Primary sensory neurons in the dorsal root ganglion (DRG) express multiple TTX-s voltage-gated sodium channel α-subunits (Navs). Since Nav1.3 increases, whereas all other Navs decrease, in the DRG neurons after peripheral nerve lesion, Nav1.3 is proposed to be critical for the generation of these spontaneous discharges and the contributions of other Navs have been ignored. Here, we re-evaluate the changes in expression of three other TTX-s Navs, Nav1.1, Nav1.6 and Nav1.7, in the injured 5th lumbar (L5) primary afferent components following L5 spinal nerve ligation (SNL) using in situ hybridization histochemistry and immunohistochemistry. While the overall signal intensities for these Nav mRNAs decreased, many injured DRG neurons still expressed these transcripts at clearly detectable levels. All these Nav proteins accumulated at the proximal stump of the ligated L5 spinal nerve. The immunostaining patterns of Nav1.6 and Nav1.7 associated with the nodes of Ranvier were maintained in the ipsilateral L5 dorsal root. Interestingly, putative proprioceptive neurons characterized by α3 Na+/K+ ATPase-immunostaining specifically lacked Nav1.7 mRNA in naïve DRG but displayed de novo expression of this transcript following SNL. Nav1.7-immunoreactive fibers were significantly increased in the ipsilateral gracile nucleus where central axonal branches of the injured A-fiber afferents terminated. These data indicate that multiple TTX-s channel subunits could contribute to the generation and propagation of the spontaneous discharges in the injured primary afferents. Specifically, Nav1.7 may cause some functional changes in sensory processing in the gracile nucleus after peripheral nerve injury.

Human ABC transporter ABCG2/BCRP expression in chemoresistance: basic and clinical perspectives for molecular cancer therapeutics

Adenine triphosphate (ATP)-binding cassette (ABC) transporter proteins, such as ABCB1/P-glycoprotein (P-gp) and ABCG2/breast cancer resistance protein (BCRP), transport various structurally unrelated compounds out of cells. ABCG2/BCRP is referred to as a “half-type” ABC transporter, functioning as a homodimer, and transports anticancer agents such as irinotecan, 7-ethyl-10-hydroxycamptothecin (SN-38), gefitinib, imatinib, methotrexate, and mitoxantrone from cells. The expression of ABCG2/BCRP can confer a multidrug-resistant phenotype on cancer cells and affect drug absorption, distribution, metabolism, and excretion in normal tissues, thus modulating the in vivo efficacy of chemotherapeutic agents. Clarification of the substrate preferences and structural relationships of ABCG2/BCRP is essential for our understanding of the molecular mechanisms underlying its effects in vivo during chemotherapy. Its single-nucleotide polymorphisms are also involved in determining the efficacy of chemotherapeutics, and those that reduce the functional activity of ABCG2/BCRP might be associated with unexpected adverse effects from normal doses of anticancer drugs that are ABCG2/BCRP substrates. Importantly, many recently developed molecular-targeted cancer drugs, such as the tyrosine kinase inhisbitors, imatinib mesylate, gefitinib, and others, can also interact with ABCG2/BCRP. Both functional single-nucleotide polymorphisms and inhibitory agents of ABCG2/BCRP modulate the in vivo pharmacokinetics and pharmacodynamics of these molecular cancer treatments, so the pharmacogenetics of ABCG2/BCRP is an important consideration in the application of molecular-targeted chemotherapies.