The significance of TNFAIP8 in prostate cancer response to radiation and docetaxel and disease recurrence

Abstract

TNFAIP8 is a NF-κB-inducible, oncogenic molecule. Previous “promoter array” studies have identified differential methylation and regulation of TNFAIP8 in prostate epithelial and cancer cell lines. Here we demonstrate that TNFAIP8 expression is induced by androgen in hormone-responsive LNCaP prostate cancer cells. In athymic mice bearing hormone-refractory PC-3 prostate tumor xenografts, intravenous treatment with a liposomal formulation of TNFAIP8 antisense oligonucleotide (LE-AS5) caused reduced expression of TNFAIP8 in tumor tissues, and a combination of LE-AS5 and radiation or docetaxel treatment resulted in significant inhibition of PC-3 tumor growth as compared to single agents. The immunohistochemical evaluation of TNFAIP8 expression revealed correlation of both cytoplasmic and nuclear TNFAIP8 overexpression with high grade prostatic adenocarcinomas, while nuclear overexpression was found to be an independent predictor of disease recurrence controlling for tumor grade. Increased nuclear TNFAIP8 expression was statistically significantly associated with a 2.44 fold (95 % confidence interval: 1.01–5.91) higher risk of prostate cancer recurrence. Mechanistically, TNFAIP8 seems to function as a scaffold (or adaptor) protein. In the antibody microarray analysis of proteins associated with the TNFAIP8 immune-complex, we have identified Karyopherin alpha2 as a novel binding partner of nuclear TNFAIP8 in PC-3 cells. The Ingenuity Pathway Analysis of the TNFAIP8 interacting proteins suggested that TNFAIP8 influences cancer progression pathways and networks involving integrins and matrix metalloproteinases. Taken together, present studies demonstrate that TNFAIP8 is a novel therapeutic target in prostate cancer, and indicate a potential relationship of the nuclear trafficking of TNFAIP8 with adverse outcomes in a subset of prostate cancer patients.

The novel p53 target TNFAIP8 variant 2 is increased in cancer and offsets p53-dependent tumor suppression

“…The last exon is common, whereas usage of other exons differs across variants (Supplementary Figure S1). Several reports have shown that TNFAIP8 is overexpressed in human cancers, [3][4][5]8,[19][20][21][22] yet none of these publications have used methods with adequate specificity to discriminate among TNFAIP8 variants. In order to determine the expression patterns of the variants in human tumors compared with normal tissue, we analyzed cataloged RNA-sequencing (RNA-seq) data from primary human tumor and normal tissue for 11 cancer types in The Cancer Genome Atlas (TCGA) (Figure 1a and Supplementary Figure S2A).…”

“…Of interest, TNFAIP8 has been proposed to be a scaffolding protein, and both p53 and PCNA were previously identified as potential TNFAIP8-binding partners. 4 It is thus intriguing to consider the possibility that v2 binding may possibly regulate access of acetylases and/or deacetylases to p53. TNFAIP8 could also conceivably regulate the activity of a signaling protein or transcription factor (other than p53 (Figure 5e)) that regulates PCNA expression.…”

“…The last exon is common, whereas usage of other exons differs across variants (Supplementary Figure S1). Several reports have shown that TNFAIP8 is overexpressed in human cancers, [3][4][5]8,[19][20][21][22] yet none of these publications have used methods with adequate specificity to discriminate among Abbreviations: BrdU, 5-bromo-2'-deoxyuridine; ChIP-seq, chromatin immunoprecipitation sequencing; DOX, doxorubicin; Gadd45A, growth arrest and DNA damageinducible 45a; H3K4me1, histone H3 mono-methylation on lysine 4; H3K4me3, histone H3 tri-methylation on lysine 4; H3K27ac, histone H3 acetylation on lysine 27; p53RE, p53 response element; PCNA, proliferating cell nuclear antigen; Scri, cells expressing scrambled shRNA; shRNA, short hairpin RNA; TCGA, The Cancer Genome Atlas; TNFAIP8, tumor necrosis factor-α-induced protein 8; TP8i, cells expressing TNFAIP8 shRNA …”

“…1,2 Although little is known about TNFAIP8, it has recently been found to be overexpressed in a wide range of human cancers. Some studies have suggested protumor functions for TNFAIP8, including enhancement of cell survival, proliferation, and metastasis [3][4][5][6][7][8][9] and resistance to cancer chemotherapeutics in mice. 4,10 Nonetheless, nothing is known about how TNFAIP8 influences responses to DNA damage in cancer cells.…”

“…Some studies have suggested protumor functions for TNFAIP8, including enhancement of cell survival, proliferation, and metastasis [3][4][5][6][7][8][9] and resistance to cancer chemotherapeutics in mice. 4,10 Nonetheless, nothing is known about how TNFAIP8 influences responses to DNA damage in cancer cells. Moreover, several transcript variants from the TNFAIP8 gene were recently registered in the NCBI reference sequence database, but no study to date has differentiated among them or defined the factors that govern their expression.…”