Philip Ryan

CWR22 has been a valuable xenograft model for the study of prostate cancer progression from an androgen-dependent tumor to one that grows in castrated animals. Herein, we report the identification and characterization of a novel androgen receptor (AR) mutation occurring in a relapsed tumor (CWR22R-2152) and in the CWR22Rv1 cell line established from it. The mutation was not detected in the original, hormone-dependent CWR22 xenograft, indicating that this change occurred during the progression to androgen independence. It is characterized by an in-frame tandem duplication of exon 3 that encodes the second zinc finger of the AR DNA-binding domain. Accordingly, immunoblot analyses demonstrated the expression of an AR species having an approximately 5-kDa increase in size relative to the LNCaP AR. This was accompanied by a COOH-terminally truncated AR species migrating with a relative mass of 75-80 kDa, referred to as ARDeltaLBD because it lacks the ligand-binding domain. By recreating the exon 3 duplication mutation in a wild-type AR expression construct, the generation of ARDeltaLBD could be recapitulated. Whereas ARDeltaLBD exhibited constitutive nuclear localization and DNA binding, these functions in the full-length AR remained androgen dependent. The CWR22Rv1 AR repertoire displayed dose-dependent, androgen-responsive transcriptional transactivation in reporter assays, albeit to a lesser extent in comparison with LNCaP. This cell line also expressed low levels of prostate-specific antigen mRNA and did not express or secrete detectable levels of prostate-specific antigen protein in androgen-depleted medium or in response to physiological androgenic stimulation. In summary, the CWR22Rv1 cell line displays both androgen-responsive and androgen-insensitive features due, at least in part, to a novel insertional mutation of the AR.

Cbl was originally discovered in 1989 as the cellular homolog of the v-Cbl oncogene, the transforming gene of the Cas NS-1 murine retrovirus that causes myeloid leukemia and lymphomas in mice. Cbl is a member of a family of RING finger ubiquitin ligases that negatively regulate signaling by tyrosine kinases and that function as adaptor proteins to regulate signaling positively. Until the past 2 years, there was little evidence that Cbl proteins were involved in human malignancies. Recent publications have shown homozygous mutations in Cbl in human myeloid neoplasms. Although in vitro and animal transformation models suggested that mutant forms of Cbl acted as an oncogene, the cellular role suggested that the protein could serve as a tumor suppressor gene. The recent data begin to reconcile this paradox as the loss of ubiquitin ligase function (the tumor suppressor function) is coupled to the maintenance of the positive signaling function (the oncogene function). These data also provide insight into potential therapeutic approaches to myeloid disorders harboring Cbl mutations.

Post-translational modifications (PTMs) of proteins are becoming the focus of intense research due to their implications in a broad spectrum of neurodegenerative diseases. Various PTMs have been identified to alter the toxic profiles of proteins which play critical roles in disease etiology. In Alzheimer's disease (AD), dysregulated phosphorylation is reported to promote pathogenic processing of the microtubule-associated tau protein. Among the PTMs, the enzymatic addition of N-acetyl-d-glucosamine (GlcNAc) residues to Ser/Thr residues is reported to deliver protective effects against the pathogenic processing of both amyloid precursor protein (APP) and tau. Modification of tau with as few as one single O-GlcNAc residue inhibits its toxic self-assembly. This modification also has the same effect on the assembly of the Parkinson's disease (PD) associated α-synuclein (ASyn) protein. In fact, O-GlcNAcylation ( O-linked GlcNAc modification) affects the processing of numerous proteins implicated in AD, PD, amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD) in a similar manner. As such, manipulation of a protein's O-GlcNAcylation status has been proposed to offer therapeutic routes toward addressing multiple neurodegenerative pathologies. Here we review the various effects that O-GlcNAc modification, and its modulated expression, have on pathogenically significant proteins involved in neurodegenerative disease.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder accounting for 60-80% of dementia cases. For many years, AD causality was attributed to amyloid-β (Aβ) aggregated species. Recently, multiple therapies that target Aβ aggregation have failed in clinical trials, since Aβ aggregation is found in AD and healthy patients. Attention has therefore shifted toward the aggregation of the tau protein as a major driver of AD. Numerous inhibitors of tau-based pathology have recently been developed. Diagnosis of AD has shifted from measuring late stage senile plaques to early stage biomarkers, amyloid-β and tau monomers and oligomeric assemblies. Synthetic peptides and some derivative structures are being explored for use as theranostic tools as they possess the capacity both to bind the biomarkers and to inhibit their pathological self-assembly. Several studies have demonstrated that O-linked glycoside addition can significantly alter amyloid aggregation kinetics. Furthermore, natural O-glycosylation of amyloid-forming proteins, including amyloid precursor protein (APP), tau, and α-synuclein, promotes alternative nonamyloidogenic processing pathways. As such, glycopeptides and related peptidomimetics are being investigated within the AD field. Here we review advancements made in the last 5 years, as well as the arrival of sugar-based derivatives.