Patricia Stanhope-Baker

Vertebrate Toll-like receptor 5 (TLR5) recognizes bacterial flagellin proteins and activates innate immune responses to motile bacteria. In addition, activation of TLR5 signaling can inhibit growth of TLR5-expressing tumors and protect normal tissues from radiation and ischemia-reperfusion injuries. To understand the mechanisms behind these phenomena at the organismal level, we assessed nuclear factor kappa B (NF-κB) activation (indicative of TLR5 signaling) in tissues and cells of mice treated with CBLB502, a pharmacologically optimized flagellin derivative. This identified the liver and gastrointestinal tract as primary CBLB502 target organs. In particular, liver hepatocytes were the main cell type directly and specifically responding to systemic administration of CBLB502 but not to that of the TLR4 agonist LPS. To assess CBLB502 impact on other pathways, we created multireporter mice with hepatocytes transduced in vivo with reporters for 46 inducible transcription factor families and found that along with NF-κB, CBLB502 strongly activated STAT3-, phenobarbital-responsive enhancer module (PREM), and activator protein 1 (AP-1-) -driven pathways. Livers of CBLB502-treated mice displayed induction of numerous immunomodulatory factors and massive recruitment of various types of immune cells. This led to inhibition of growth of liver metastases of multiple tumors regardless of their TLR5 status. The changed liver microenvironment was not, however, hepatotoxic, because CBLB502 induced resistance to Fas-mediated apoptosis in normal liver cells. Temporary occlusion of liver blood circulation prevented CBLB502 from protecting hematopoietic progenitors in lethally irradiated mice, indicating involvement of a factor secreted by responding liver cells. These results define the liver as the key mediator of TLR5-dependent effects in vivo and suggest clinical applications for TLR5 agonists as hepatoprotective and antimetastatic agents.

Nickolay Neznanov 1 , Andrei P. Komarov 2 , Lubov Neznanova 1 , Patricia Stanhope-Baker 3 and Andrei V. Gudkov 1,3 1 Department of Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, NY 14263 2 Cellecta, Inc. Mountain View, CA 94043 3 Cleveland BioLabs, Inc., Buffalo, NY 14263 Received: March 18, 2011; Accepted: March 27, 2011; Published: March 27, 2011; Keywords: bortezomib, puromycin, hyperthermia, heat shock, apoptosis, cancer treatment, translation, ubiquitination, protein degradation, protein denaturing Correspondence: Andrei V. Gudkov, e-mail: // // Abstract Proteotoxic stress (PS) is generated in cells under a variety of conditions involving accumulation of misfolded proteins. To avoid the toxicity of unmitigated PS, cells activate the heat shock response (HSR). HSR involves upregulation of factors such as ubiquitin and the non-housekeeping chaperone Hsp70 which assist with metabolism of aberrant proteins. The PS-HSR axis is a potential anticancer treatment target since many tumor cells display constitutive PS and dependence on HSR due to their rapid rates of proliferation and translation. In fact, induction of PS via stimulation of protein misfolding (hyperthermia), inhibition of proteasomes (bortezomib) or inhibition of Hsp90 (geldanamycin) have all been considered or used for cancer treatment. We found that combination of bortezomib with an inducer of protein misfolding (hyperthermia or puromycin) resulted in enhanced PS. HSR was also induced, but could not mitigate the elevated PS and the cells died via largely p53-independent apoptosis. Thus, combination treatments were more cytotoxic in vitro than the component single treatments. Consistent with this, combination of non-toxic doses of puromycin with bortezomib significantly increased the antitumor activity of bortezomib in a mouse model of multiple myeloma. These results provide support for using combination treatments that disrupt the balance of PS and HSR to increase the therapeutic index of anticancer therapies.

Antigen receptor genes are assembled from their component gene segments by a highly regulated series of site-specific DNA recombination reactions known as V(D)J recombination. Proteins encoded by the RAG1 and RAG2 genes are responsible for the recognition and double-stranded cleavage of a highly conserved DNA sequence flanking all rearranging gene segments. It remains uncertain how this common lymphoid recombinase is targeted to distinct loci in developing B and T cells and to specific loci at successive stages of lymphocyte development. This review considers evidence that DNA sequences which regulate the transcription of antigen receptor genes also regulate the recombination reaction by determining the accessibility of individual loci to the V(D)J recombinase.