Cancer Cell Signaling PathwaysResearch Team Leader Wiesława Widłak, Ph. D., Dr. Sci.

Major objectives of research:

Research activities of the Cancer Cell Signaling Pathways group focus around the transcription factor HSF1 (Heat Shock Factor 1). We analyze signaling pathways that are activated by HSF1, especially in stressful conditions. We examine interactions between HSF1-dependent and estrogen-dependent or NF-κB-dependent pathways. The activation of HSF1 is an important element of the heat shock response, which also supports tumorigenesis. Currently, the main topic of our research isto clarify the mechanisms leading to HSF1 activation by estrogen (17-β-estradiol, E2) in non-cancerous and cancerous breast epithelial cells. We also want to determine the contribution of HSF1 in an estrogen-inducd neoplastic transformation and in maintaining tumor growth.

In response to proteotoxic stress (e.g. heat shock), leading to HSF1 activation, cytoprotective mechanisms or apoptotic cell death are induced.The molecular mechanisms involved in switching from pro-survival signaling to pro-death signaling in cells subjected to hyperthermia are not fully understood. We postulate that these two opposite processes can be directly regulated by HSF1. In heat-resistant cells, HSF1 activates the expression of genes encoding cytoprotective HSPs (Heat Shock Proteins), which prevent apoptosis. In heat-sensitive cells (such as spermatocytes) heat stress leads to global transcription inhibition. SPEN (SPEN homolog, transcriptional regulator; msx2- interacting protein) is one of a few genes whose expression in spermatogenic cells is up-regulated due to the activation of HSF1. Thus, we examine the involvement of SPEN protein in the transcription regulation in mouse spermatogenic cells, particularly during heat shock. The aim of our research is also to characterize the heat shock response in different cells which differ in their sensitivity to stress. In particular we study the regulation of the expression and the function of proapoptotic proteins activated during stress which were selected in our previous analysis.

Mouse gene 3110001I22Rik, coding for LOC66598 protein, was discovered by scientists from the RIKEN institute in Yokohama as part of the The RIKEN integrated database of mammals project. The gene is located on the 16th chromosome in the first intron of the Bfar gene, and its function remains unknown. Gene 3110001I22Rik was chosen by us as a result of microarray experiments, which showed an increase expression after heat shock. Preliminary experiments suggest that the LOC66598 protein may have pro-apoptotic properties. In silico research indicated its likely domains: LGE and rich in serine. Both they may be significant in the proper functioning of the LOC66598 protein.

PMAIP1/NOXA is the primary p53-responsive gene, a member of the BCL-2 protein family. Its overexpression leads to apoptosis. We found that HSF1 (heat shock transcription factor 1) is also involved in Pmaip1 regulation. Based on functional genomic studies we identified HSF1 binding to its consensus binding sites (HSEs), interestingly located in the Pmaip1 introns, and we found Pmaip1 to be the most induced gene by constitutively active, mutated HSF1 in juvenile testes of transgenic mice (which initiated spermatocytes apoptosis leading to infertility in males). We observed that heat shock also up-regulated the Pmaip1 transcription in mouse spermatocytes. Then we found similar HSF1 binding and up-regulation of Pmaip1/PMAIP1 transcription connected with protein accumulation in certain somatic human and mouse cell lines and tissues.

In cooperation with the Silesian University of Technology we execute the project considering interactions between HSF1-dependent and NF-κB-dependent pathways. In cells exposed to heat shock, activation of NF-κB is inhibited in spite of stimulation (eg. by TNFα cytokine). The aim of the research is to find the "time window", in which NF-κB is most effectively blocked after heat shock and to explain the mechanism. We are also looking for differences in HSF1/NF-κB signaling between normal and cancer cells. For the purposes of modelling (using bioinformatic tools) interactions between HSF1 and NF-κB we created cell lines with expression of these transcription factors labelled with red or green fluorescence proteins (for live-imaging microscopy).


Keywords: neoplastic transformation, cellular stress, apoptosis, cytoprotection, heat shock proteins, HSF1, estrogen, NFκB, ChIP-Seq, RNA-Seq


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