A Phase I Study of the Cyclin-Dependent Kinase 4/6 Inhibitor Ribociclib (LEE011) in Patients with Advanced Solid Tumors and Lymphomas.

Purpose: Ribociclib (an oral, highly specific cyclin-dependent kinase 4/6 inhibitor) inhibits tumor growth in preclinical models with intact retinoblastoma protein (Rb). This first-in-human study investigated the MTD, recommended dose for expansion (RDE), safety, preliminary activity, pharmacokinetics, and pharmacodynamics of ribociclib in patients with Rb advanced solid tumors or lymphomas.

Experimental Design: Patients received escalating doses of ribociclib (3-weeks-on/1-week-off or continuous).

Tumor cells can follow distinct evolutionary paths to become resistant to epidermal growth factor receptor inhibition.

Although mechanisms of acquired resistance of epidermal growth factor receptor (EGFR)-mutant non-small-cell lung cancers to EGFR inhibitors have been identified, little is known about how resistant clones evolve during drug therapy. Here we observe that acquired resistance caused by the EGFR(T790M) gatekeeper mutation can occur either by selection of pre-existing EGFR(T790M)-positive clones or via genetic evolution of initially EGFR(T790M)-negative drug-tolerant cells. The path to resistance impacts the biology of the resistant clone, as those that evolved from drug-tolerant cells had a diminished apoptotic response to third-generation EGFR inhibitors that target EGFR(T790M); treatment with navitoclax, an inhibitor of the anti-apoptotic factors BCL-xL and BCL-2 restored sensitivity.

The ALK inhibitor ceritinib overcomes crizotinib resistance in non-small cell lung cancer.

Unlabelled: Non-small cell lung cancers (NSCLC) harboring anaplastic lymphoma kinase (ALK) gene rearrangements invariably develop resistance to the ALK tyrosine kinase inhibitor (TKI) crizotinib. Herein, we report the first preclinical evaluation of the next-generation ALK TKI, ceritinib (LDK378), in the setting of crizotinib resistance. An interrogation of in vitro and in vivo models of acquired resistance to crizotinib, including cell lines established from biopsies of patients with crizotinib-resistant NSCLC, revealed that ceritinib potently overcomes crizotinib-resistant mutations.

Variants on a theme: a biomarker of crizotinib response in ALK-positive non-small cell lung cancer?

Anaplastic lymphoma kinase (ALK) gene rearrangements are found in approximately 5% of non-small cell lung carcinoma patients and confer sensitivity to ALK inhibitors such as crizotinib. The particular ALK fusion expressed may have an impact on protein stability and sensitivity to crizotinib, and this may underlie the heterogeneity in responses observed in the clinic.

New targets in advanced NSCLC: EML4-ALK.

Targeted therapies aimed at inhibiting oncogenic tyrosine kinases are becoming commonplace in the treatment of cancer. The EML4-ALK fusion gene was first identified as a potentially targetable oncogenic driver in non-small cell lung cancer in 2007. A small molecule ALK inhibitor, crizotinib, may now be on the verge of approval by the US Food and Drug Administration for the treatment of ALK-rearranged lung cancer.

N-glycosylation of human nicastrin is required for interaction with the lectins from the secretory pathway calnexin and ERGIC-53.

The gamma-secretase complex, composed of four non-covalently bound transmembrane proteins Presenilin, Nicastrin (NCT), APH-1 and PEN-2, is responsible for the intramembranous cleavage of amyloid precursor protein (APP), Notch and several other type I transmembrane proteins. gamma-Secretase cleavage of APP releases the Abeta peptides, which form the amyloid plaques characteristic of Alzheimer's disease brains, and cleavage of Notch releases an intracellular signalling peptide that is critical for numerous developmental processes. NCT, a type I membrane protein, is the only protein within the complex that is glycosylated.

Presenilin modulates Pen-2 levels posttranslationally by protecting it from proteasomal degradation.

The gamma-secretase complex functions to cleave several type I transmembrane proteins within their transmembrane domains. These include the amyloid precursor protein, which is central to Alzheimer's disease pathogenesis, as well as N-cadherin and Notch, which regulate transcription. This complex is composed of four requisite integral membrane proteins: presenilin 1 (PS1) or presenilin 2 (PS2), nicastrin, Pen-2, and Aph-1.

Membrane topology and nicastrin-enhanced endoproteolysis of APH-1, a component of the gamma-secretase complex.

APH-1, presenilin, nicastrin, and Pen-2 are proteins with varying membrane topologies that compose the gamma-secretase complex, which is responsible for the intramembrane proteolysis of several substrates including the amyloid precursor protein. APH-1 is known to be necessary for gamma-secretase activity, but its precise function in the complex is not fully understood, and its membrane topology has not been described, although it is predicted to traverse the membrane seven times. To investigate this, we used selective permeabilization of the plasma membrane and immunofluorescence microscopy to show that the C terminus of the APH-1 resides in the cytosolic space.

A comparison of amyloid fibrillogenesis using the novel fluorescent compound K114.

Proteinaceous inclusions with amyloidogenic properties are a common link between many neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. Histological and in vitro studies of amyloid fibrils have advanced the understanding of protein aggregation, and provided important insights into pathogenic mechanisms of these neurodegenerative brain amyloidoses. The classical amyloid dyes Congo Red (CR) and thioflavin T and S, have been used extensively to detect amyloid inclusions in situ.

The transmembrane domain region of nicastrin mediates direct interactions with APH-1 and the gamma-secretase complex.

Nicastrin (NCT) is a type I integral membrane protein that is one of the four essential components of the gamma-secretase complex, a protein assembly that catalyzes the intramembranous cleavage of the amyloid precursor protein and Notch. Other gamma-secretase components include presenilin-1 (PS1), APH-1, and PEN-2, all of which span the membrane multiple times. The mechanism by which NCT associates with the gamma-secretase complex and regulates its activity is unclear.

Membrane topology of gamma-secretase component PEN-2.

PEN-2 is an integral membrane protein that is a necessary component of the gamma-secretase complex, which is central in the pathogenesis of Alzheimer's disease and is also required for Notch signaling. In the absence of PEN-2, Notch signaling fails to guide normal development in Caenorhabditis elegans, and amyloid beta peptide is not generated from the amyloid precursor protein. Human PEN-2 is a 101-amino acid protein containing two putative transmembrane domains.