DNA polymerase kappa (POLkappa) is a low fidelity translesional DNA polymerase implicated in spontaneous and DNA damage-induced mutagenesis. We have previously shown that POLkappa was frequently overexpressed in human lung cancer tissues as compared with their matched non-tumorous tissue counterpart. In the present study, we found a close correlation between elevated POLkappa expression and p53 inactivation in lung cancer tissues. To investigate whether POLK expression might be regulated by p53, we have determined the transcriptional initiation site of POLK gene and examined its promoter activity in A549, H358-129, and PC-3 human lung cancer cell lines. Wild-type p53, but not a mutant p53 (R273H) devoid of the DNA-binding activity, strongly inhibited POLK promoter activity in these cells. In addition, POLK promoter exhibited a significantly higher activity in p53-/- murine embryo fibroblasts (MEF) than in p53+/- and p53+/+ MEF. These results link p53 status with POLkappa expression and suggest that loss of p53 function may in part contribute to the observed POLkappa upregulation in human lung cancers.

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Calf spleen extractive injection (CSEI), extracted from the spleen of healthy cows (within 24 h of birth), is a small peptides enriched extraction while the ratio between peptide and ribose is 76 AE 15.2 mg/lg. CSEI is usually used as an ancillary agent to assist cancer patients with immune dysfunction. The present study aims to evaluate the immunomodulatory activity of CSEI in cyclophosphamide (CTX)-induced mice model of immunosuppression and its underlying mechanisms. During the experiment, thymosin ɑ1 (0.16 mg/kg) was served as the positive control drug. In CTX-induced immunosuppressed mice, CSEI significantly increased bodyweights and spleen indexes, and upgraded the natural killer activity together with lymphocytes proliferation. CSEI regulated the production of IgG and IgA, and the levels of IL-2, 6, 10, 12 and IFN-ɑ, c and TNF-ɑ in serum of CTX-induced immunosuppressed mice. Furthermore, CSEI markedly downregulated nuclear factor kappa-B (NF-jB) expression which was controlled by IKKb. Taken together, CSEI effectively improved immune function in CTX-induced immunosuppression related to NF-jB signalling pathway via regulating the production of immunoglobulins, interleukins and some inflammatory factors.