We report the surprising finding that common germline polymorphisms of APOE, present in approximately 39% of Caucasians, predict survival outcomes in human melanoma. Analysis of The Cancer Genome Atlas revealed that carriers of the APOE2 variant experienced shorter survival relative to APOE3 homozygotes, while APOE4 variant carriers exhibited increased survival.Consistent with this, melanoma growth in human APOE knock-in mice followed the order of APOE2 > APOE3 > APOE4, revealing causal regulation of progression by APOE variants. Mechanistically, recombinant ApoE protein variants differentially suppressed melanoma cell invasion and endothelial recruitment phenotypes. Moreover, tumors in APOE4 mice exhibited greater immune cell infiltration and activation relative to tumors of APOE2 mice. These findings support the notion that human germline genetic makeup can impact the trajectory of a future malignancy.The secreted glycoprotein Apolipoprotein E (ApoE) was previously found to suppress melanoma progression and metastasis through cancer cell autonomous and non-autonomous mechanisms (1-3). In humans there are three prevalent ApoE variants termed ApoE2, ApoE3, and ApoE4, which differ in only two amino acids and exhibit differential binding to ApoE receptors (Fig. 1a)(4-7). The APOE4 variant is the strongest monogenetic risk factor for Alzheimer's disease, while APOE2 confers reduced risk for this disease (8,9). APOE variants also modulate the risk for cardiovascular disease (reviewed in ( 10)). Given their high prevalence in the general population, the association of APOE variants with a number of human phenotypic outcomes has been investigated. However, a causal role for these variants in disease pathogenesis has only been demonstrated for Alzheimer's disease and atherosclerosis through the use of murine models (11,12). The potential association between APOE status and cancer outcomes has remained inconclusive (13,14).Given prior evidence supporting a role for ApoE in melanoma progression, we investigated the association between germline APOE variant status and clinical outcome of patients with advanced localized melanoma (stages II-III) by determining APOE genotypes from normal tissue whole exome sequencing data of

Structural alterations in DNA can serve as natural impediments to replication fork stability and progression, resulting in DNA damage and genomic instability. Naturally occurring polypurine mirror repeat sequences in the human genome can create endogenous triplex structures evoking a robust DNA damage response. Failures to recognize or adequately process these genomic lesions can result in loss of genomic integrity. Nucleotide excision repair (NER) proteins have been found to play a prominent role in the recognition and repair of triplex structures. We demonstrate using triplex-forming oligonucleotides that chromosomal triplexes perturb DNA replication fork progression, eventually resulting in fork collapse and the induction of double strand breaks (DSBs). We find that cells deficient in the NER damage recognition proteins, XPA and XPC, accumulate more DSBs in response to chromosomal triplex formation than NER-proficient cells. Furthermore, we demonstrate that XPC-deficient cells are particularly prone to replication-associated DSBs in the presence of triplexes. In the absence of XPA or XPC, deleterious consequences of triplex-induced genomic instability may be averted by activating apoptosis via dual phosphorylation of the H2AX protein. Our results reveal that damage recognition by XPC and XPA is critical to maintaining replication fork integrity and preventing replication fork collapse in the presence of triplex structures.

Disruption of the tumor suppressor PTEN, either at the protein or genomic level, plays an important role in human cancer development. The high frequency of PTEN deficiency reported across several cancer subtypes positions therapeutic approaches that exploit PTEN loss-of-function with the ability to significantly impact the treatment strategies of a large patient population. Here, we report that an endophytic fungus isolated from a medicinal plant produces an inhibitor of DNA double-strand-break repair. Furthermore, the novel alkaloid product, which we have named irrepairzepine (1), demonstrated synthetic lethal targeting in PTEN-deficient glioblastoma cells. Our results uncover a new therapeutic lead for PTEN-deficient cancers and an important molecular tool toward enhancing the efficacy of current cancer treatments.

The secreted lipid transporter apolipoprotein E (APOE) plays important roles in atherosclerosis and Alzheimer's disease and has been implicated as a suppressor of melanoma progression. APOE germline genotype predicts human melanoma outcomes, as APOE4 and APOE2 allele carriers exhibit increased versus reduced melanoma survival, respectively, relative to APOE3 homozygotes. While the APOE4 variant was recently shown to suppress melanoma progression by enhancing anti-tumor immunity, the melanoma cell-intrinsic effects of APOE variants on cancer progression remain poorly characterized. By using a genetically engineered mouse model, we show that human germline APOE genetic variants differentially modulate melanoma growth and metastasis in a melanoma LRP1 receptor-dependent manner. We identify protein synthesis as a tumor cell-intrinsic process differentially modulated by APOE variants, with APOE2 surprisingly promoting translation via LRP1. Our findings reveal a gain-of-function role for the APOE2 variant in melanoma progression, raising important implications for other diseases impacted by APOE genetics.

We report the surprising finding that common germline polymorphisms of APOE, present in approximately 39% of Caucasians, predict survival outcomes in human melanoma. Analysis of The Cancer Genome Atlas revealed that carriers of the APOE2 variant experienced shorter survival relative to APOE3 homozygotes, while APOE4 variant carriers exhibited increased survival. Consistent with this, melanoma growth in human APOE knock-in mice followed the order of APOE2 > APOE3 > APOE4, revealing causal regulation of progression by APOE variants. Mechanistically, recombinant ApoE protein variants differentially suppressed melanoma cell invasion and endothelial recruitment phenotypes. Moreover, tumors in APOE4 mice exhibited greater immune cell infiltration and activation relative to tumors of APOE2 mice. These findings support the notion that human germline genetic makeup can impact the trajectory of a future malignancy.

The secreted lipid transporter apolipoprotein E (APOE) plays important roles in atherosclerosis and Alzheimer’s disease and has been implicated as a suppressor of melanoma progression. The APOE germline genotype predicts human melanoma outcomes, with APOE4 and APOE2 allele carriers exhibiting prolonged and reduced survival, respectively, relative to APOE3 homozygotes. While the APOE4 variant was recently shown to suppress melanoma progression by enhancing anti-tumor immunity, further work is needed to fully characterize the melanoma cell-intrinsic effects of APOE variants on cancer progression. Using a genetically engineered mouse model, we showed that human germline APOE genetic variants differentially modulate melanoma growth and metastasis in an APOE2>APOE3>APOE4 manner. The LRP1 receptor mediated the cell-intrinsic effects of APOE variants on melanoma progression. Protein synthesis was a tumor cell-intrinsic process differentially modulated by APOE variants, with APOE2 promoting translation via LRP1. These findings reveal a gain-of-function role for the APOE2 variant in melanoma progression, which may aid in predicting melanoma patient outcomes and understanding the protective effect of APOE2 in Alzheimer’s disease.