Opposite Effects of the Overexpression of Protein Kinase Cγ and δ on the Growth Properties of Human Glioma Cell Line U251 MG

The protein kinase C-η isoform induces proliferation in glioblastoma cell lines through an ERK/Elk-1 pathway

“…One explanation for the conflict is that individual glioblastomas express unique profiles of PKC isozymes (Couldwell et al, 1990;Pollack et al, 1991;Szaniawska et al, 1996). PKC-a has been implicated in proliferation and in suppression of apoptosis (Shen and Glazer, 1998), whereas PKC-g augments anchorage-independent growth in cell culture (Mishima et al, 1994).…”

“…We compared the response to PMA in U-251 cell to that of U-1242 cells. U-251 cells express PKC-Z (Mishima et al, 1994) but the U-1242 line do not (Hussaini et al, 2000). PMA increases the mitogenic response in U-251 cells, and inhibits the mitogenic response in U-1242 cells.…”

“…Different PKC isoforms have been associated with different proliferation rates of neoplastic astrocytes. For example, in the U-251 MG glioblastoma cell line (U-251), Mishima et al (1994), reported that stable overexpression of PKC-g is associated with increased growth, whereas PKC-d is associated with decreased growth. Therefore, a given PKC isotype may dictate the degree of the proliferative response to phorbol 12-myristate 13-acetate (PMA).…”

Phorbol 12-Myristate 13-Acetate Induces Protein Kinase Cη-specific Proliferative Response in Astrocytic Tumor Cells

“…The differential expression of PKC isozymes, each mediating diverse biologic functions, could account for the contrasting effects of phorbol esters on specific biologic activities in astrocytic tumors (33-35). Likewise, this PKC isozyme diversity also could account for the apparently different cellular responses following the expression or overexpression of specific PKC isozymes (18,17,36).…”

“…Both human and experimental rodent gliomas express multiple classes of PKC isozymes, including PKC-␣, -␤, -␥, -␦, -⑀, -, -, and - (17)(18)(19)(20)(21). In cultured human and rat glioma cells, the differential expression of specific isozymes accompanies alterations in both proliferative activity and phenotypic differentiation that are related to specific cell lineages.…”