Retinoblastoma protein expressed in human non-Hodgkin's lymphoma cells generates resistance against radiation-induced apoptosis

Inactivation of the retinoblastoma susceptibility (Rb) gene has been observed in various cancers. Nevertheless, in several cancer cases, including non-Hodgkin's lymphoma, previous investigations showed that the Rb gene product (pRb) was abundantly expressed with varying degree. Here we report the THS-SP1.1 cell line isolated from non-Hodgkin's lymphoma. The THS-SP1.1 cells abundantly expressed pRb and showed resistance against radiation-induced apoptosis. Culture with the antisense phosphorothioate oligonucleotide complementary to the Rb gene augmented the apoptosis of THS-SP1.1 cells after radiation, whereas the control oligonucleotides did not. These data showed that pRb abundantly expressed in the lymphoma cells inhibited radiation-induced apoptosis.