Browsing by Author "Li, Xin"
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Item The Association Between Citrus Consumption and Skin Cancer: An Analysis of Risk and Nutrient-Gene Interaction(2020-12) Marley, Andrew Raymond; Han, Jiali; Sibg, Yiqing; Li, Xin; Li, Ming; Champion, Victoria L.Purpose. In the US, melanoma and non-melanoma skin cancer (NMSC) rates have increased substantially in recent decades. While many skin cancer risk factors have been established, the impact of dietary citrus, which is naturally abundant in photocarcinogenic psoralens, remains enigmatic. The purpose of this research was to investigate associations between citrus consumption and risks of melanoma and NMSC, and to conduct a genome-wide study to identify genetic variants that may modify this association. Methods. Participants from the UK Biobank were leveraged for these analyses. Citrus consumption was collected via five rounds of 24-hour recall questionnaires, with complete citrus data available for n=210,126 participants. Ascertainment of melanoma and NMSC cases were identified by international classification of disease codes via linkage with national registries. Logistic regression was used to estimate odds ratios and 95% confidence intervals for the associations between citrus consumption and skin cancer outcomes. Individual citrus products were assessed for independent associations with skin cancer risk, and established skin cancer risk factors were tested for interaction. Joint 2-degree-of-freedom (df) and 1-df tests were used to assess interaction between total citrus consumption and genetic variants. Results. After controlling for covariates, high total citrus consumption was significantly associated with increased melanoma risk, an association primarily driven by orange and orange juice consumption. Skin color was found to be a significant effect modifier for the association between total citrus consumption and melanoma risk, but only before adjusting for multiple comparisons. No significant associations were observed for high total citrus consumption or consumption of any individual citrus products and NMSC risk. Significant associations for half a serving of citrus consumption and NMSC risk were likely due to chance or confounding. Index SNPs on chromosomes 3, 9, and 16 were significant according to the joint 2-df test, and 7 SNPs on chromosome 16 displayed evidence of a citrus-gene interaction. Conclusion. My analyses provide evidence in support of high citrus consumption significantly increasing risk of melanoma, but not NMSC. I also identified SNPs on AFG3L1P that may modify this association. Future research should further explore these associations, particularly for NMSC and to confirm my genetic findings.Item Association between indoor tanning frequency during early life and other potentially addictive behaviors among US women(Elsevier, 2021) Tsibris, Hillary C.; Nan, Hongmei; Li, Xin; Global Health, School of Public HealthItem Association of genetic variants of TMEM135 and PEX5 in the peroxisome pathway with cutaneous melanoma-specific survival(AME Publishing, 2021-03) Wang, Haijiao; Liu, Hongliang; Dai, Wei; Luo, Sheng; Amos, Christopher I.; Lee, Jeffrey E.; Li, Xin; Yue, Ying; Nan, Hongmei; Wei, Qingyi; Epidemiology, School of Public HealthBackground: Peroxisomes are ubiquitous and dynamic organelles that are involved in the metabolism of reactive oxygen species (ROS) and lipids. However, whether genetic variants in the peroxisome pathway genes are associated with survival in patients with melanoma has not been established. Therefore, our aim was to identify additional genetic variants in the peroxisome pathway that may provide new prognostic biomarkers for cutaneous melanoma (CM). Methods: We assessed the associations between 8,397 common single-nucleotide polymorphisms (SNPs) in 88 peroxisome pathway genes and CM disease-specific survival (CMSS) in a two-stage analysis. For the discovery, we extracted the data from a published genome-wide association study from The University of Texas MD Anderson Cancer Center (MDACC). We then replicated the results in another dataset from the Nurse Health Study (NHS)/Health Professionals Follow-up Study (HPFS). Results: Overall, 95 (11.1%) patients in the MDACC dataset and 48 (11.7%) patients in the NHS/HPFS dataset died of CM. We found 27 significant SNPs in the peroxisome pathway genes to be associated with CMSS in both datasets after multiple comparison correction using the Bayesian false-discovery probability method. In stepwise Cox proportional hazards regression analysis, with adjustment for other covariates and previously published SNPs in the MDACC dataset, we identified 2 independent SNPs (TMEM135 rs567403 C>G and PEX5 rs7969508 A>G) that predicted CMSS (P=0.003 and 0.031, respectively, in an additive genetic model). The expression quantitative trait loci analysis further revealed that the TMEM135 rs567403 GG and PEX5 rs7969508 GG genotypes were associated with increased and decreased levels of mRNA expression of their genes, respectively. Conclusions: Once our findings are replicated by other investigators, these genetic variants may serve as novel biomarkers for the prediction of survival in patients with CM.Item Characterization of a Bioengineered AAV3B Capsid Variant with Enhanced Hepatocyte Tropism and Immune Evasion(Liebert, 2023-04) Rana, Jyoti; Marsic, Damien; Zou, Chenhui; Muñoz-Melero, Maite; Li, Xin; Kondratov, Oleksandr; Li, Ning; de Jong, Ype P.; Zolotukhin, Sergei; Biswas, Moanaro; Pediatrics, School of MedicineCapsid engineering of adeno-associated virus (AAV) can surmount current limitations to gene therapy such as broad tissue tropism, low transduction efficiency, or pre-existing neutralizing antibodies (NAb) that restrict patient eligibility. We previously generated an AAV3B combinatorial capsid library by integrating rational design and directed evolution with the aim of improving hepatotropism. A potential isolate, AAV3B-DE5, gained a selective proliferative advantage over five rounds of iterative selection in hepatocyte spheroid cultures. In this study, we reanalyzed our original dataset derived from the AAV3B combinatorial library and isolated variants from earlier (one to three) rounds of selection, with the assumption that variants with faster replication kinetics are not necessarily the most efficient transducers. We identified a potential candidate, AAV3B-V04, which demonstrated significantly enhanced transduction in mouse-passaged primary human hepatocytes as well as in humanized liver chimeric mice, compared to the parental AAV3B or the previously described isolate, AAV3B-DE5. Interestingly, the AAV3B-V04 capsid variant exhibited significantly reduced seroreactivity to pooled or individual human serum samples. Forty-four percent of serum samples with pre-existing NAbs to AAV3B had 5- to 20-fold lower reciprocal NAb titers to AAV3B-V04. AAV3B-V04 has only nine amino acid substitutions, clustered in variable region IV compared to AAV3B, indicating the importance of the loops at the top of the three-fold protrusions in determining both transduction efficiency and immunogenicity. This study highlights the effectiveness of rational design combined with targeted selection for enhanced AAV transduction via molecular evolution approaches. Our findings support the concept of limiting selection rounds to isolate the best transducing AAV3B variant without outgrowth of faster replicating candidates. We conclude that AAV3B-V04 provides advantages such as improved human hepatocyte tropism and immune evasion and propose its utility as a superior candidate for liver gene therapy.Item Citrus Consumption and Risk of Non-Melanoma Skin Cancer in the UK Biobank(Taylor & Francis, 2022) Marley, Andrew R.; Li, Ming; Champion, Victoria L.; Song, Yiqing; Han, Jiali; Li, Xin; Epidemiology, School of Public HealthBackground: Non-melanoma skin cancer (NMSC) incidence has been dramatically increasing worldwide. Psoralen, a known photocarcinogen, is naturally abundant in citrus products, leading to the hypothesis that high citrus consumption may increase NMSC risk. Methods: We fitted age- and multivariable-adjusted logistic regression models to evaluate the association between citrus consumption and NMSC risk among 197,372 UKBB participants. A total of 9,613 NMSC cases were identified using International Classification of Disease 10 codes. Citrus consumption data were collected via five rounds of 24-hour recall questionnaires. Results: We found no association between high total citrus consumption and NMSC risk, although a slightly elevated NMSC risk was observed among participants who consumed >0 to half a serving of total citrus per day (OR [95% CI] = 1.08 [1.01-1.16]). There was no association between individual citrus products and NMSC risk. Conclusion: High citrus consumption was not associated with an increased risk of NMSC in our UKBB sample. Further studies are needed to clarify these associations. Supplemental data for this article is available online at https://doi.org/10.1080/01635581.2021.1952439 .Item Citrus-Gene Interaction and Melanoma Risk in the UK Biobank(Wiley, 2022) Marley, Andrew R.; Li, Ming; Champion, Victoria L.; Song, Yiqing; Han, Jiali; Li, Xin; Epidemiology, School of Public HealthHigh citrus consumption may increase melanoma risk; however, little is known about the biological mechanisms of this association, or whether it is modified by genetic variants. We conducted a genome-wide analysis of gene-citrus consumption interactions on melanoma risk among 1563 melanoma cases and 193 296 controls from the UK Biobank. Both the 2-degrees-of-freedom (df) joint test of genetic main effect and gene-environment (G-E) interaction and the standard 1-df G-E interaction test were performed. Three index SNPs (lowest P-value SNP among highly correlated variants [r2 > .6]) were identified from among the 365 genome-wide significant 2-df test results (rs183783391 on chromosome 3 [MITF], rs869329 on chromosome 9 [MTAP] and rs11446223 on chromosome 16 [DEF8]). Although all three were statistically significant for the 2-df test (4.25e-08, 1.98e-10 and 4.93e-13, respectively), none showed evidence of interaction according to the 1-df test (P = .73, .24 and .12, respectively). Eight nonindex, 2-df test significant SNPs on chromosome 16 were significant (P < .05) according to the 1-df test, providing evidence of citrus-gene interaction. Seven of these SNPs were mapped to AFG3L1P (rs199600347, rs111822773, rs113178244, rs3803683, rs73283867, rs78800020, rs73283871), and one SNP was mapped to GAS8 (rs74583214). We identified several genetic loci that may elucidate the association between citrus consumption and melanoma risk. Further studies are needed to confirm these findings.Item Comprehensive Comparison of AAV Purification Methods: Iodixanol Gradient Centrifugation vs. Immuno-Affinity Chromatography(Hindawi, 2023) Lam, Anh K.; Mulcrone, Patrick L.; Frabutt, Dylan; Zhang, Junping; Chrzanowski, Matthew; Arisa, Sreevani; Munoz, Maite; Li, Xin; Biswas, Moanaro; Markusic, David; Herzog, Roland W.; Xiao, Weidong; Pediatrics, School of MedicineRecombinant adeno-associated viruses (AAVs) have emerged as a widely used gene delivery platform for both basic research and human gene therapy. To ensure and improve the safety profile of AAV vectors, substantial efforts have been dedicated to the vector production process development using suspension HEK293 cells. Here, we studied and compared two downstream purification methods, iodixanol gradient ultracentrifugation versus immuno-affinity chromatography (POROS™ CaptureSelect™ AAVX column). We tested multiple vector batches that were separately produced (including AAV5, AAV8, and AAV9 serotypes). To account for batch-to-batch variability, each batch was halved for subsequent purification by either iodixanol gradient centrifugation or affinity chromatography. In parallel, purified vectors were characterized, and transduction was compared both in vitro and in vivo in mice (using multiple transgenes: Gaussia luciferase, eGFP, and human factor IX). Each purification method was found to have its own advantages and disadvantages regarding purity, viral genome (vg) recovery, and relative empty particle content. Differences in transduction efficiency were found to reflect batch-to-batch variability rather than disparities between the two purification methods, which were similarly capable of yielding potent AAV vectors.Item Cumulative Erythemal Ultraviolet Radiation and Risk of Cancer in 3 Large US Prospective Cohorts(Oxford University Press, 2022) Chang, Michael S.; Hartman, Rebecca I.; Trepanowski, Nicole; Giovannucci, Edward L.; Nan, Hongmei; Li, Xin; Epidemiology, School of Public HealthUltraviolet radiation (UVR) exposure is the major risk factor for melanoma. However, epidemiologic studies on UVR and noncutaneous cancers have reported inconsistent results, with some suggesting an inverse relationship potentially mediated by vitamin D. To address this, we examined 3 US prospective cohorts, the Health Professionals Follow-up Study (HPFS) (1986) and Nurses’ Health Study (NHS) I and II (1976 and 1989), for associations between cumulative erythemal UVR and incident cancer risk, excluding nonmelanoma skin cancer. We used a validated spatiotemporal model to calculate erythemal UVR. Participants (47,714 men; 212,449 women) were stratified into quintiles by cumulative average erythemal UVR, using the first quintile as referent, for Cox proportional hazards regression analysis. In the multivariable-adjusted meta-analysis of all cohorts, compared with the lowest quintile, risk of any cancer was slightly increased across all other quintiles (highest quintile hazard ratio (HR) = 1.04, 95% confidence interval (CI): 1.01, 1.07; P for heterogeneity = 0.41). All UVR quintiles were associated with similarly increased risk of any cancer excluding melanoma. As expected, erythemal UVR was positively associated with risk of melanoma (highest quintile HR = 1.17, 95% CI: 1.04, 1.31; P for heterogeneity = 0.83). These findings suggest that elevated UVR is associated with increased risk of both melanoma and noncutaneous cancers.Item Cutaneous nevi and internal cancer risk: Results from two large prospective cohorts of US women(Wiley, 2020-07) Li, Xin; Wu, Wenting; Giovannucci, Edward; Stampfer, Meir J.; Gao, Xiang; Han, Jiali; Epidemiology, School of Public HealthElevated cutaneous nevus number has been linked to longer telomeres. Recently, a large systematic Mendelian randomization study identified a significant positive association between telomere length and risk of cancer. Here, we hypothesized that higher nevus count, as a phenotypic marker of longer telomere, may be associated with increased risk of internal cancer, and prospectively examined the association between nevus count and total as well as site‐specific cancer risk among participants in the Nurses’ Health Study (NHS, 1986–2012) and the Nurses’ Health Study 2 (NHS2, 1989–2013) using Cox proportional hazards models. During 3,900,264 person‐years of follow‐up, we documented a total of 23,004 internal cancer cases (15,484 in the NHS and 7,520 in the NHS2). Compared to participants who had no nevi, the multivariate hazard ratios of total cancer (excluding skin cancer) were 1.06 (95% confidence interval [CI], 1.03–1.09) for women with 1–5 nevi, 1.08 (95% CI, 1.03–1.15) for those who had 6–14 nevi and 1.19 (95% CI, 1.05–1.35) for those with 15 or more nevi (p trend <0.0001). Moreover, because nevus count has been associated with risk of breast cancer previously, we conducted a secondary analysis by excluding breast cancer from the outcomes of interest. The results were very similar to those of our primary analysis. For individual cancer, most of the associations with nevus count were positive but not statistically significant. In conclusion, we identified the number of cutaneous nevi as a phenotypic marker associated with internal cancer risk, which may be explained by telomere biology.Item Effect of CpG Depletion of Vector Genome on CD8+ T Cell Responses in AAV Gene Therapy(Frontiers Media, 2021-05-31) Bertolini, Thais B.; Shirley, Jamie L.; Zolotukhin, Irene; Li, Xin; Kaisho, Tsuneyasu; Xiao, Weidong; Kumar, Sandeep R.P.; Herzog, Roland W.; Pediatrics, School of MedicineAdeno associated viral (AAV) vectors have emerged as a preferred platform for in vivo gene replacement therapy and represent one of the most promising strategies to treat monogenetic disorders such as hemophilia. However, immune responses to gene transfer have hampered human gene therapy in clinical trials. Over the past decade, it has become clear that innate immune recognition provides signals for the induction of antigen-specific responses against vector or transgene product. In particular, TLR9 recognition of the vector's DNA genome in plasmacytoid dendritic cells (pDCs) has been identified as a key factor. Data from clinical trials and pre-clinical studies implement CpG motifs in the vector genome as drivers of immune responses, especially of CD8+ T cell activation. Here, we demonstrate that cross-priming of AAV capsid-specific CD8+ T cells depends on XCR1+ dendritic cells (which are likely the main cross-presenting cell that cooperates with pDCs to activate CD8+ T cells) and can be minimized by the elimination of CpG motifs in the vector genome. Further, a CpG-depleted vector expressing human coagulation factor IX showed markedly reduced (albeit not entirely eliminated) CD8+ T cell infiltration upon intramuscular gene transfer in hemophilia B mice when compared to conventional CpG+ vector (comprised of native sequences), resulting in better preservation of transduced muscle fibers. Therefore, this deimmunization strategy is helpful in reducing the potential for CD8+ T cell responses to capsid or transgene product. However, CpG depletion had minimal effects on antibody responses against capsid or transgene product, which appear to be largely independent of CpG motifs.