James Wang

TRAF Family Proteins Interact with the Common Neurotrophin Receptor and Modulate Apoptosis Induction

The common neurotrophin receptor, p75NTR, has been shown to signal in the absence of Trk tyrosine kinase receptors, including induction of neural apoptosis and activation of NF-κB. However, the mechanisms by which p75NTR initiates these intracellular signal transduction pathways are unknown. Here we report interactions between p75NTR and the six members of TRAF (tumor necrosis factor receptor-associated factors) family proteins. The binding of different TRAF proteins to p75NTR was mapped to distinct regions in p75NTR. Furthermore, TRAF4 interacted with dimeric p75NTR, whereas TRAF2 interacted preferentially with monomeric p75NTR. TRAF2-p75NTR, TRAF4-p75NTR, and TRAF6-p75NTR interactions modulated p75NTR-induced cell death and NF-κB activation with contrasting effects. Coexpression of TRAF2 with p75NTRenhanced cell death, whereas coexpression of TRAF6 was cytoprotective. Furthermore, overexpression of TRAF4 abrogated the ability of dimerization to prevent the induction of apoptosis normally mediated by monomeric p75NTR. TRAF4 also inhibited the NF-κB response, whereas TRAF2 and TRAF6 enhanced p75NTR-induced NF-κB activation. These results demonstrate that TRAF family proteins interact with p75NTR and differentially modulate its NF-κB activation and cell death induction.

Nell-1, a key functional mediator of Runx2, partially rescues calvarial defects in Runx2+/− mice

Mesenchymal stem cell commitment to an osteoprogenitor lineage requires the activity of Runx2, a molecule implicated in the etiopathology of multiple congenital craniofacial anomalies. Through promoter analyses, we have recently identified a new direct transcriptional target of Runx2, Nell‐1, a craniosynostosis (CS)–associated molecule with potent osteogenic properties. This study investigated the mechanistic and functional relationship between Nell‐1 and Runx2 in regulating osteoblast differentiation. The results showed that spatiotemporal distribution and expression levels of Nell‐1 correlated closely with those of endogenous Runx2 during craniofacial development. Phenotypically, cross‐mating Nell‐1 overexpression transgenic (CMV‐Nell‐1) mice with Runx2 haploinsufficient (Runx2+/−) mice partially rescued the calvarial defects in the cleidocranial dysplasia (CCD)–like phenotype of Runx2+/− mice, whereas Nell‐1 protein induced mineralization and bone formation in Runx2+/− but not Runx2−/− calvarial explants. Runx2‐mediated osteoblastic gene expression and/or mineralization was severely reduced by Nell‐1 siRNA oligos transfection into Runx2+/+ newborn mouse calvarial cells (NMCCs) or in N‐ethyl‐N‐nitrosourea (ENU)–induced Nell‐1−/− NMCCs. Meanwhile, Nell‐1 overexpression partially rescued osteoblastic gene expression but not mineralization in Runx2 null (Runx2−/−) NMCCs. Mechanistically, irrespective of Runx2 genotype, Nell‐1 signaling activates ERK1/2 and JNK1 mitogen‐activated protein kinase (MAPK) pathways in NMCCs and enhances Runx2 phosphorylation and activity when Runx2 is present. Collectively, these data demonstrate that Nell‐1 is a critical downstream Runx2 functional mediator insofar as Runx2‐regulated Nell‐1 promotes osteoblastic differentiation through, in part, activation of MAPK and enhanced phosphorylation of Runx2, and Runx2 activity is significantly reduced when Nell‐1 is blocked or absent.

Neurotrophin dependence mediated by p75NTR: contrast between rescue by BDNF and NGF.

During development, neurons pass through a critical phase in which survival is dependent on neurotrophin support. In order to dissect the potential role of p75NTR, the common neurotrophin receptor, in neurotrophin dependence, we expressed wild-type and mutant p75NTR in cells that do not express endogenous p75NTR or Trk family members (NIH3T3). Expression of wild-type p75NTR created a state of neurotrophin dependence: cells could be rescued by nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), or neurotrophin-3 (NT-3), but not by a mutant NGF that binds well to Trk A but poorly to p75NTR. Similarly, expression of p75NTR in human prostate cancer cells in culture rendered a metastatic tumor cell line (PC-3) sensitive to the availability of neurotrophins for survival. Moreover, expression of mutant p75NTRs in another neurotrophin-insensitive cell line (HEK293T) showed that a domain within the intracellular domain governs alternate responses to neurotrophins: the carboxy terminus of the intracellular domain of p75NTR including the sixth alpha helix domain is necessary for rescue by BDNF, but not NGF. These results, when considered with previous studies of the timing of p75NTR expression, support the hypothesis that p75NTR is a mediator of neurotrophin dependence during the critical phase of developmental cell death and during the progression of carcinogenesis in prostate cancer.

Outcomes of multiple myeloma patients receiving bortezomib, lenalidomide, and carfilzomib

New classes of drugs including the proteasome inhibitors (PI) bortezomib and, more recently, carfilzomib and the immunomodulatory agent lenalidomide have shown improved outcomes for multiple myeloma (MM) patients during the past decade. However, most of the studies reporting outcomes for patients receiving these drugs have relied on older data sets derived from large institutions that included patients not receiving their treatment at those facilities and represented only those eligible for clinical trials or were from sites where treatment options were limited. We have analyzed data from 258 MM patients who have received treatment with at least one of three agents: bortezomib, carfilzomib, and lenalidomide in a single clinic specializing in MM with respect to their responses and other outcomes to treatment regimens including these agents. Response rates were similar between these three drugs when used for the first time and again during subsequent treatment regimens. As expected, the clinical benefit rates (CBRs) were better for patients receiving their first treatment when compared to their use in subsequent treatment regimens. The CBRs were similar during their 2nd, 3rd, and 4th treatments containing these agents. Many patients refractory to these agents showed responses to regimens containing these same drugs when used in different combinations. In addition, patients refractory to one PI often responded to the other PI. The results of this study demonstrate that novel agents can be used repeatedly in novel combinations with significant clinical benefit for patients with MM.

Risk of skin cancer in multiple myeloma patients: a retrospective cohort study.

Immunosuppressed patients are known to have an increased incidence of skin cancer. Patients with multiple myeloma (MM) show impaired immune function. In the past, because of poor survival, the incidence of specific secondary primary malignancies such as skin cancer among these patients was difficult to establish. With more effective MM therapies that have emerged in recent years, these patients are living markedly longer, and therefore, it becomes of increasing importance to determine whether their risk of developing other medical problems such as skin cancer is increased. We performed a retrospective cohort study of 205 myeloma patients and 193 age‐, race‐, and gender‐matched control subjects to assess the incidence of skin cancers among patients with MM and determine the specific types of and risk factors for skin cancer. We found that there is an increased occurrence of skin cancer among patients with MM compared to control subjects (26.8% vs. 16.1% in controls; P = 0.009). Among specific types of skin cancer, the proportion of patients with squamous cell carcinoma (SCC) was higher than controls (P = 0.016). In addition to MM diagnosis, older age and Caucasian ethnicity were predictors of skin cancer of any type. Furthermore, older age was also a predictor of SCC.