ABSTRACT
Tumor progression is a complex process that involves the interaction of cancer cells with the cancer-surrounding stromal cells. The cancer stroma influences the cancer cell growth and metastatic potential. The EGF family growth factor HB-EGF is synthesized in cancer cells and plays pivotal roles in oncogenic transformation and tumor progression, but the contribution of HB-EGF expressed in tumor stromal cells to tumor growth remains unclear. In the present study, we found that HB-EGF was expressed in host-derived cancer stromal cells in xenograft and allograft mouse tumor models. CRM197 is a specific inhibitor of human HB-EGF that has no effect on mouse HB-EGF. To elucidate whether host-derived stromal HB-EGF contributes to tumor growth, we generated knock-in mice expressing a CRM197-inhibitable humanized mutant form of HB-EGF. Administration of CRM197 to humanized knock-in mice that were bearing tumors derived from human or mouse cancer cells revealed that inhibition of host-derived stromal HB-EGF by CRM197 significantly reduced tumor growth. These results suggest that HB-EGF in the cancer-associated stroma plays a significant role for tumor growth, and that the HB-EGF derived from the stroma, as well as that expressed by cancer cells, is a potential target for cancer therapy. The present results also suggest that the humanized HB-EGF knock-in mice could be utilized for pathophysiological studies of HB-EGF as well as the development of therapeutic strategies targeting HB-EGF.
Subject(s)
Intercellular Signaling Peptides and Proteins/genetics , Neoplasms/etiology , Animals , Bacterial Proteins/therapeutic use , Cell Line, Tumor , Disease Models, Animal , Disease Progression , Gene Knock-In Techniques , Heparin-binding EGF-like Growth Factor , Humans , Intercellular Signaling Peptides and Proteins/metabolism , Mice , Mice, Nude , Neoplasms/drug therapy , Neoplasms/pathology , Stromal Cells/metabolism , Transplantation, Heterologous , Transplantation, HomologousABSTRACT
Although circadian transcription of Period2 (Per2) is fundamental for the generation of circadian rhythm, the molecular mechanism remains unclear. Here we report that cell-autonomous circadian transcription of Per2 is driven by two transcriptional elements, one for rhythm generation and the other for phase control. The former contains the E-box-like sequence (CACGTT) that is sufficient and indispensable to drive oscillation, and indeed circadian transcription factors site-specifically bind to it. Furthermore, the nature of this atypical E-box is different from that of the classical circadian E-box. The current feedback loop model is based mainly on Period1. Our results provide not only compelling evidence in support of this model but also an explanation for a general basic mechanism to produce various patterns in the phase and amplitude of cell-autonomous circadian gene expression.
