Jörg Kaufmann

Phase I clinical development of Atu027, a siRNA formulation targeting PKN3 in patients with advanced solid tumors

Chemically synthesized, small interfering RNAs (siRNA) are currently used as a new class of therapeutic molecules, allowing the controlled down-regulation of pathologically relevant gene expression e.g., oncogenes and other similar targets in cancer [1, 2, 3].However, the overall negative charge of siRNA molecules (up to 40 negative charg-es) and the relatively high molecular weight (12,000 – 14,000 Da) prevent the functional uptake of these novel therapeutic molecules in vivo. Besides the inefficient uptake and the degradation in endosomal compartments at the cellular level, non-formulated siRNAs are rapidly cleared by renal excretion from the blood stream when administered i.v. [4].To overcome these limitations, a variety of non-viral nanoparticles (50 – 200 nm) have been recently developed enabling chemically synthesized siRNA to be used therapeuti-cally for inhibition of RNAi-mediated tumor growth. Atu027 is a novel RNAi therapeutic agent based on cationic lipoplexes containing chemically stabilized siRNAs, which target Protein Kinase N3 (PKN3) gene expression in the vascular endothelium (Figure 1) [5]. PKN3, a member of the AGC kinase fam-ily, has been identified as a promising, novel therapeutic target in cancer cells for inhibiting tumor progression and lymph node metasta-sis formation [6]. These studies have revealed that PKN3 mediates malignant cell growth downstream of the chronically activated phosphoinositide 3-kinase (PI3K) pathway [6]. Recently, PKN3 has also been considered as a suitable therapeutic target for modulating tumor-associated angiogenesis. Preclinical data, obtained in various cancer mouse mod-els, revealed target-specific, RNAi-mediated silencing of PKN3 expression and significant inhibition of tumor progression and metasta-sis formation [

CIF150, a Human Cofactor for Transcription Factor IID-Dependent Initiator Function

ABSTRACT The transcription factor IID (TFIID) complex is highly conserved between the Drosophila and mammalian systems. A mammalian homolog has been described for all the Drosophila TATA box-binding protein-associated factors (TAFs), with the exception of dTAFII150. We previously reported the identification of CIF, an essential cofactor for TFIID-dependent transcription from promoters containing initiator (Inr) elements. Here we describe the molecular cloning of CIF150, the human homolog of dTAFII150, and present biochemical evidence that this factor is involved in Inr activity. CIF150 is capable of mediating TFIID-dependent Inr activity in a complementation assay, and a protein fraction lacking Inr activity lacks detectable amounts of CIF150. Despite the striking similarity to dTAFII150, CIF150 does not appear to be associated with human TFIID. However, in vitro binding assays revealed a specific and direct interaction between CIF150 and hTAFII135. This interaction might be structurally important for the functional interaction between CIF150 and human TFIID, since CIF150 stabilizes TFIID binding to a core promoter.

Human Transcription Factor hTAFII150 (CIF150) Is Involved in Transcriptional Regulation of Cell Cycle Progression

ABSTRACT Here we present evidence that CIF150 (hTAFII150), the human homolog of Drosophila TAFII150, plays an important and selective role in establishing gene expression patterns necessary for progression through the cell cycle. Gel filtration experiments demonstrate that CIF150 (hTAFII150) seems to be less tightly associated with human transcription factor IID than hTAFII130 is associated with hTAFII250. The transient functional knockout of CIF150 (hTAFII150) protein led to cell cycle arrest at the G2/M transition in mammalian cell lines. PCR display analysis with the RNA derived from CIF150-depleted cells indicated that CIF150 (hTAFII150) is required for the transcription of only a subset of RNA polymerase II genes. CIF150 (hTAFII150) directly stimulated cyclin B1 and cyclin A transcription in cotransfection assays and in vitro assays, suggesting that the expression of these genes is dependent on CIF150 (hTAFII150) function. We defined a CIF150 (hTAFII150) consensus binding site and demonstrated that a CIF150-responsive cis element is present in the cyclin B1 core promoter. These results suggest that one function of CIF150 (hTAFII150) is to select specific RNA polymerase II core promoter elements involved in cell cycle progression.

Depletion of protein kinase N3 (PKN3) impairs actin and adherens junctions dynamics and attenuates endothelial cell activation

Several pathways are involved in the control of endothelial cell morphology, endothelial permeability and function in order to maintain vascular homeostasis. Here we report that protein kinase N3 (PKN3) appears to play a pivotal role in maintaining endothelial cell morphology, cell-cell junctions and motility. An RNAi-based cell biological approach in cultured human endothelial cells (HUVEC) revealed that knockdown of PKN3 expression gave rise to cells with divergent cell morphology, impaired locomotion, disturbed adherens junctions (AJ) integrity and irregular actin organization. Notably, knockdown of PKN3 cells led to improper stress fiber formation and marked adhesiveness of intercellular adherens junctions when cells became stimulated with the pro-inflammatory cytokine TNF-α. Moreover, TNF-α-induced ICAM-1 expression on the cell surface was reduced in cells with suppressed PKN3 expression. Finally, loss-of-function for PKN3 appeared to affect Pyk2 phosphorylation in endothelial cells. These observations suggest that PKN3 can be considered a novel protein implicated in remodeling the actin-adherens junction, possibly by linking ICAM-1-signaling with actin/AJ dynamics. We propose that loss of PKN3 function and concomitant aberrations in actin rearrangement may attenuate pro-inflammatory activation of endothelial cells.