A Germline DNA Polymorphism Enhances Alternative Splicing of the KLF6 Tumor Suppressor Gene and Is Associated with Increased Prostate Cancer Risk

Abstract

Prostate cancer is a leading and increasingly prevalent cause of cancer death in men. Whereas family history of disease is one of the strongest prostate cancer risk factors and suggests a hereditary component, the predisposing genetic factors remain unknown. We first showed that KLF6 is a tumor suppressor somatically inactivated in prostate cancer and since then, its functional loss has been further established in prostate cancer cell lines and other human cancers. Wild-type KLF6, but not patient-derived mutants, suppresses cell growth through p53-independent transactivation of p21. Here we show that a germline KLF6 single nucleotide polymorphism, confirmed in a tri-institutional study of 3,411 men, is significantly associated with an increased relative risk of prostate cancer in men, regardless of family history of disease. This prostate cancer-associated allele generates a novel functional SRp40 DNA binding site and increases transcription of three alternatively spliced KLF6 isoforms. The KLF6 variant proteins KLF6-SV1 and KLF6-SV2 are mislocalized to the cytoplasm, antagonize wtKLF6 function, leading to decreased p21 expression and increased cell growth, and are up-regulated in tumor versus normal prostatic tissue. Thus, these results are the first to identify a novel mechanism of selfencoded tumor suppressor gene inactivation and link a relatively common single nucleotide polymorphism to both regulation of alternative splicing and an increased risk in a major human cancer. (Cancer Res 2005; 65(4): 1213-22)

Non-random subcellular distribution of variant EKLF in erythroid cells

“…For example, KLF6 is expressed in multiple spliced isoforms that are not equivalently segregated, leading to significant downstream consequences [41]. In the present studies, different forms of EKLF are enriched in the cytoplasm versus the nucleus as visualized during SDS-PAGE, which may arise from alterative splicing.…”

KLF4, p21 and context-dependent opposing forces in cancer

“…Recently, a single-nucleotide polymorphism (SNP) in KLF6 has been identified that correlates with an increased relative risk of prostate cancer 67 . It is associated with increased production of three alternatively spliced, dominant-negative KLF6 isoforms.…”

KLF6 and TP53 mutations are a rare event in prostate cancer: distinguishing between Taq polymerase artifacts and true mutations

“…30,[36][37][38][39] The role that KLF6 polymorphisms play in increasing the risk of developing prostate cancer is also controversial. Narla et al 40 proposed that the presence of a germline single-nucleotide polymorphism (SNP) (IVS1 -27G4A) in KLF6 could produce a splicing variant that would reduce the activation of p21. This polymorphism was associated with an increased risk for prostate cancer, 40 but subsequent reports have shown contradictory results.…”

“…Narla et al 40 proposed that the presence of a germline single-nucleotide polymorphism (SNP) (IVS1 -27G4A) in KLF6 could produce a splicing variant that would reduce the activation of p21. This polymorphism was associated with an increased risk for prostate cancer, 40 but subsequent reports have shown contradictory results. 32,[41][42][43][44] Moreover, the R201R polymorphism of KLF6 has been reported to be of marginal importance in the predisposition of developing prostate cancer in a series of Finnish hereditary prostate cancer patients.…”