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The DNA-damage-signaling pathway has been implicated in all human cancers. However, the genetic defects and the mechanisms of this pathway in prostate carcinogenesis remain poorly understood. In this study, we analyzed CHEK2, the upstream regulator of p53 in the DNA-damage-signaling pathway, in several groups of patients with prostate cancer. A total of 28 (4.8%) germline CHEK2 mutations (16 of which were unique) were found among 578 patients. Additional screening for CHEK2 mutations in 149 families with familial prostate cancer revealed 11 mutations (5 unique) in nine families. These mutations included two frameshift and three missense mutations. Importantly, 16 of 18 unique CHEK2 mutations identified in both sporadic and familial cases were not detected among 423 unaffected men, suggesting a pathological effect of CHEK2 mutations in prostate cancer development. Analyses of the two frameshift mutations in Epstein Barr virus-transformed cell lines, using reverse-transcriptase polymerase chain reaction and western blot analysis, revealed abnormal splicing for one mutation and dramatic reduction of CHEK2 protein levels in both cases. Overall, our data suggest that mutations in CHEK2 may contribute to prostate cancer risk and that the DNA-damage-signaling pathway may play an important role in the development of prostate cancer.

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Genetic defects in CHEK2 and TP53 have been implicated in prostate cancer development. However, the interaction of these two genes in prostate cancer tumorigenesis has not been investigated. We previously described 11 CHEK2 mutations in a group of 84 primary prostate tumors. In this report, we screened the same group of tumors for TP53 mutations and revealed nine somatic and two germline mutations. One germline TP53 mutation (c.408A>T/p.Gln136His) and two somatic mutations (c.1022T>G/p.Phe341Cys and c.108-109ins22/p.His37fsX13) are novel to human cancer. More interestingly, CHEK2 and TP53 mutations were observed to be mutually substituted in these tumors. Analysis of five commonly used prostate cancer cell lines revealed that four cell lines harboring TP53 mutations carry no CHEK2 mutation while the only cell line (LNCaP) carrying wild-type TP53 harbors a CHEK2 mutation. The novel CHEK2 mutation (c.1160C>T/p.Thr387Asn) identified in LNCaP cells changes amino acid Thr387 to Asn which has been shown to impair CHEK2 autophosphorylation and activation. Our data suggest that the CHEK2 and TP53 mutations can substitute each other in at least 25% (21/84) of prostate cancers and that DNA damage-signaling pathway plays an important role in prostate cancer tumorigenesis. Published

These data are consistent with the hypothesis that the LH-beta variant is a weak risk factor for prostate cancer.

African American (AA) families have the highest risk of prostate cancer (PC). However, the genetic defects contributing to PC in these families remain poorly understood. We performed Whole-exome sequencing of one affected and one unaffected brother in a large AA family with hereditary PC. The novel non-synonymous variants discovered only in the affected were analyzed in all affected and unaffected men in twenty AA-PC families. Here, we report one rare recurrent ADPRHL1 germline mutation (c.A233T; p.D78V) in four of the twenty families. The mutation co-segregates with PC in two families and presents in two affected men in other two, but was absent in 170 unrelated healthy AA men. The mutation expressed in benign prostate cells showed aberrant promotion of cell proliferation while expression of the wild-type ADPRHL1 in PC cells suppressed cell proliferation and oncogenesis. Mechanistically, the ADPRHL1 mutant activates PARP1 leading to an increased H2O2 or cisplatin induced DNA damage response for PC cell survival. Indeed, the PARP1 inhibitor, Olaparib, suppresses PC cell survival induced by mutant ADPRHL1. Given that the expression levels of ADPRHL1 are significantly high in normal prostate tissues and reduce as Gleason scores increase in tumors, our findings provide genetic, biochemical, and clinic-pathological evidence that ADPRHL1 is a tumor suppressor in prostate. A loss of function mutation in ADPRHL1 induces prostate tumorigenesis and confers PC susceptibility in high-risk AA families. Implications: This study highlighted a potential strategy of ADPRHL1 mutation detection in PC risk assessment and a potential therapeutic application for those within AA-PC families.

The speckle-type POZ protein (SPOP) is a tumor suppressor in prostate cancer (PCa). SPOP somatic mutations have been reported in up to 15% of PCa of those of European descent. However, the genetic roles of SPOP in African American (AA)-PCa are currently unknown. We sequenced the SPOP gene to identify somatic mutations in 49 AA prostate tumors and identified three missense mutations (p.Y87C, p.F102S, and p.G111E) in five AA prostate tumors (10%) and one synonymous variant (p.I106I) in one tumor. Intriguingly, all of mutations and variants clustered in exon six, and all of the mutations altered conserved amino acids. Moreover, two mutations (p.F102S and p.G111E) have only been identified in AA-PCa to date. Quantitative real-time polymerase chain reaction analysis showed a lower level of SPOP expression in tumors carrying SPOP mutations than their matched normal prostate tissues. In addition, SPOP mutations and novel variants were detected in 5 of 27 aggressive PCa and one of 22 less aggressive PCa (P < 0.05). Further studies with increased sample size are needed to validate the clinicopathological significance of these SPOP mutations in AA-PCa.

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