Monoclonal antibodies to epidermal growth factor receptors in studies of receptor structure and function

Progranulin/GP88, A Complex and Multifaceted Player of Tumor Growth by Direct Action and via the Tumor Microenvironment

Investigation of the role of progranulin/GP88 on the proliferation and survival of a wide variety of cells has been steadily increasing. Several human diseases stem from progranulin dysregulation either through its overexpression in cancer or its absence as in the case of null mutations in some form of frontotemporal dementia. The present review focuses on the role of progranulin/GP88 in cancer development, progression, and drug resistance. Various aspects of progranulin identification, biology, and signaling pathways will be described. Information will be provided about its direct role as an autocrine growth and survival factor and its paracrine effect as a systemic factor as well as via interaction with extracellular matrix proteins and with components of the tumor microenvironment to influence drug resistance, migration, angiogenesis, inflammation, and immune modulation. This chapter will also describe studies examining progranulin/GP88 tumor tissue expression as well as circulating level as a prognostic factor for several cancers. Due to the wealth of publications in progranulin, this review does not attempt to be exhaustive but rather provide a thread to lead the readers toward more in-depth exploration of this fascinating and unique protein.

The effect of ionizing radiation on signal transduction: antibodies to EGF receptor sensitize A431 cells to radiation

What determines the degree of cell-resistance or sensitivity to ionizing radiation is not yet known. As a corollary to the ability of ceramide to induce apoptosis, some questions arise as to whether malignant cells escape apoptosis because of their inability to mount a ceramide response to inducers of apoptosis. To shed more light on the molecular mechanisms of tumor cell response to radiation, we tested whether exposure to ionizing radiation (of 200-1000 cGy) is associated with changes in ceramide levels in A431 tumor epithelial cells and whether the ability of ceramide to induce apoptosis is inhibited by protein kinase C (PKC) activation. Our studies demonstrate an immediate decrease in cellular levels of ceramide in response to radiation, while sphingosine levels increase. Under the same conditions the cellular 1,2-diacylglycerol (DAG) levels decrease as well, being accompanied by the translocation of PKC alpha from the membrane to the cytoplasm. Elevation of membrane PKC levels by 12-O-tetradecanoylphorbol 13-acetate (TPA) treatment had no effect on cell survival after irradiation, while treatment with EGF during and after irradiation augmented cell survival. Moreover, monoclonal antibodies to the EGF receptor (EGFR) sensitize cells to radiation by facilitating radiation-induced apoptosis. It is thus plausible that in human Squamous carcinoma cells, radiation activates predominantly the EGFR to induce resistance, while both sphingomyelin and PKC signal transduction pathways are deactivated and demonstrate no significant role in the modulation of the sensitivity or the resistance of A431 cells to ionizing radiation.

Explant organ culture: a review

Organ explant culture models offer several significant advantages for studies of patho-physiologic mechanisms like cell injury, secretion, differentiation and structure development. Organs or small explants/slices can be removed in vivo and maintained in vitro for extended periods of time if careful attention is paid to the media composition, substrate selection, and atmosphere. In the case of human tissues obtained from autopsy or surgery, additional attention must be paid to the postmortem interval, temperature, hydration, and cause of death. Explant organ culture has been effectively utilized to establish outgrowth cell cultures and characterize the histiotypic relationships between the various cell types within an organ or tissue.