Biomedical subjects

Xin Lin

Publications and source records attributed to Xin Lin.

At least 19 recordsLinked to original sources

PubMed2025

Transitioning from native to synthetic receptors: broadening T-cell engineering and beyond.

T-cell immunotherapy has progressed rapidly, evolving from native T-cell receptor biology to the development of innovative synthetic receptors that extend therapeutic applications beyond cancer. This review explores engineering strategies, ranging from natural TCRs to synthetic receptors, that increase T-cell activation and therapeutic potential. We begin by highlighting the foundational role of native receptors in the T-cell response, emphasizing how these structural and functional insights inform the design of next-generation synthetic receptors. Comparisons between CAR and TCR-like synthetic receptors underscore their respective advantages in specificity, efficacy, and safety, as well as potential areas for further improvement. In addition, gene editing technologies such as CRISPR-Cas9 enable precise modifications to the T-cell genome, enhancing receptor performance and minimizing immunogenic risks. In addition to tumors, these engineered T cells can be directed against viral infections, autoimmune disorders, and other diseases. We also explore advanced strategies that engage multiple immune cell types to achieve synergistic, durable responses. By demonstrating how native and synthetic receptors collectively drive innovation, this review aims to inspire new research directions and ultimately expand the scope of T-cell engineering for universal therapeutic applications.

Humans↗

PubMed2007

Genetic polymorphism in bladder cancer.

Individual variation in the genetic constitution of humans may affect the host responses to constant assaults from exogenous and endogenous carcinogens, which will eventually impact cancer risk, disease prognosis and clinical outcome. Bladder cancer is one of the most common cancers in the world. In this review, the published research articles studying the association between genetic polymorphisms and bladder cancer risk and disease progression are summarized. Genetic polymorphisms are categorized based on their primary cellular functions: genes in carcinogen metabolism, DNA repair, cell cycle control, inflammation, apoptosis, methylation, genes functioning as G proteins, and cell adhesion molecules. Furthermore, we discuss a number of limitations of current genetic susceptibility research and suggest future directions in molecular epidemiology study. This review presents an overview of current molecular epidemiology of bladder cancer and provides a useful resource for understanding the pathogenesis of bladder cancer.

Apoptosis↗

PubMed2007

B cell lymphoma 10 is essential for FcepsilonR-mediated degranulation and IL-6 production in mast cells.

The adaptor protein B cell lymphoma 10 (Bcl10) plays an essential role in the functions of the AgRs in T and B cells. In this study, we report that Bcl10 also plays an important role in mast cells. Bcl10 is expressed in mast cells. Although Bcl10-deficient mast cells undergo normal development, we demonstrate that Bcl10 is essential for specific functions of FcepsilonR. Although Bcl10-deficient mast cells have normal de novo synthesis and release of the lipid mediator arachidonic acid, the mutant cells possess impaired FcepsilonR-mediated degranulation, indicated by decreased serotonin release, and impaired cytokine production, measured by release of IL-6. In addition, Bcl10-deficient mice display impaired IgE-mediated passive cutaneous anaphylaxis. Moreover, although Bcl10-deficient mast cells have normal FcepsilonR-mediated Ca(2+) flux, activation of PI3K, and activation of the three types of MAPKs (ERKs, JNK, and p38), the mutant cells have markedly diminished FcepsilonR-mediated activation of NF-kappaB and decreased activation of AP-1. Thus, Bcl10 is essential for FcepsilonR-induced activation of AP-1, NF-kappaB, degranulation, and cytokine production in mast cells.

Adaptor Proteins, Signal Transducing↗

PubMed2007

High-order interactions among genetic variants in DNA base excision repair pathway genes and smoking in bladder cancer susceptibility.

Cancer is a common multifactor human disease resulting from complex interactions between many genetic and environmental factors. In this study, we used a multifaceted analytic approach to explore the relationship between eight single nucleotide polymorphisms in base excision repair (BER) pathway genes, smoking, and bladder cancer susceptibility in a hospital-based case-control study. Overall, we did not find an association between any single BER gene single nucleotide polymorphism and bladder cancer risk. However, in stratified analysis, the OGG1 S326C variant genotypes in ever smokers (odds ratio, 0.74; 95% confidence interval, 0.56-0.99) and ADP-ribosyltransferase (ADPRT) V762A variant genotypes in never smokers (odds ratio, 0.58; 95% confidence interval, 0.37-0.91) conferred a significantly reduced risk. Using logistic regression, we observed that there was a two-way interaction between ADPRT V762A and smoking status. We next used classification and regression tree analysis to explore high-order gene-gene and gene-environment interactions. We found that smoking is the most important influential factor for bladder cancer risk. Consistent with the above findings, we found that the ADPRT V762A was only significantly involved in bladder cancer risk in never smokers and the OGG1 S326C was only significantly involved in ever smokers. We also observed gene-gene interactions among OGG1 S326C, XRCC1 R194W, and MUTYH H335Q in ever smokers. Using multifactor dimensionality reduction approach, the four-factor model, including smoking status, OGG1 S326C (rs1052133), APEX1 D148E (rs3136820), and ADPRT762 (rs1136410), had the best ability to predict bladder cancer risk with the highest cross-validation consistency (100%) and the lowest prediction error (37.02%; P < 0.001). These results support the hypothesis that genetic variants in BER genes contribute to bladder cancer risk through gene-gene and gene-environmental interactions.

Algorithms↗

PubMed2006

The CARMA1-Bcl10 signaling complex selectively regulates JNK2 kinase in the T cell receptor-signaling pathway.

Members of the c-Jun NH(2)-terminal kinase (JNK) family play crucial roles in cell activation, differentiation, and apoptosis. Although many studies have indicated that JNK1 and JNK2 have functional differences and redundancy, the upstream signaling pathway that selectively activates JNK1 or JNK2 remains unknown. In this study, we have revealed a selective mechanism of JNK activation, in which JNK2, but not JNK1, was regulated by CARMA1, a scaffold molecule, after stimulation of the T cell receptor (TCR). This CARMA1-dependent regulation of JNK2 worked through the scaffold molecule Bcl10, which was inducibly associated with JNK2 and served as a JNK-interacting protein (JIP)-like scaffold to assemble the kinases JNK2, MKK7, and TAK1. Finally, we showed that CARMA1- and Bcl10-mediated JNK2 activation had a critical role in regulating the amount of c-Jun protein. Together, our studies provide genetic evidence that JNK1 and JNK2 are differentially regulated in the TCR-signaling pathway and play different functions.

Animals↗

PubMed2006

The adaptor protein CARD9 is required for innate immune responses to intracellular pathogens.

The caspase-recruitment domain-containing adaptor protein CARD9 regulates the innate signaling responses to fungal infection. Here we show that CARD9 is required for innate immune responses against intracellular pathogens. We generated Card9(-/-) mice and found that CARD9-deficient macrophages had defects in activation of the kinases p38 and Jnk but not of transcription factor NF-kappaB after bacterial and viral infection. CARD9-deficient mice failed to clear infection and showed altered cytokine production after challenge with Listeria monocytogenes. In wild-type cells, we found CARD9 inducibly associated with both the intracellular 'biosensor' Nod2 and the serine-threonine kinase RICK. Our data demonstrate that CARD9 has a critical function in Nod2-mediated activation of p38 and Jnk in innate immune responses to intracellular pathogens.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Bcl10 plays a critical role in NF-kappaB activation induced by G protein-coupled receptors.

G protein-coupled receptors (GPCRs) play pivotal roles in cell proliferation, differentiation, and survival. Although many studies indicate that the stimulation of GPCRs leads to NF-kappaB activation, the molecular mechanism by which GPCRs induced NF-kappaB activation remains largely unknown. Bcl10 is an essential adaptor molecule connecting antigen receptor signaling cascades to NF-kappaB activation in lymphocytes. However, the function of Bcl10 in nonlymphoid cells remains to be determined. In this study, we demonstrated that the deficiency of Bcl10 resulted in the defect in NF-kappaB activation induced by either expressing the constitutively active mutant of G protein or stimulation of cells with lysophosphatidic acid or endothelin-1, which activate their GPCR. In contrast, TNF-alpha-, LPS-, and integrin-induced NF-kappaB activation was not affected in Bcl10-deficient cells. Together, our results provide genetic evidence showing that Bcl10 is a key signaling component mediating NF-kappaB activation induced by GPCRs in nonlymphoid cells.

Adaptor Proteins, Signal Transducing↗

PubMed2006

Microtransponders, the miniature RFID electronic chips, as platforms for cell growth in cytotoxicity assays.

BACKGROUND: An electronic radio frequency (RF) microchip, the microtransponder (MTP), has been developed as a platform for assays in the fields of genomics and proteomics. Upon activation by light, each MTP provides a unique RF identification (ID) signal that matches a chip to the specific biological material attached to it. The MTP is powered by a photocell and has an antenna that transmits the signal. The aim of the present study was to explore utility of MTPs as a platform for cell growth in cytotoxicity assays. METHODS: The MCF-7, MCF-116, A549, or T-24 cells growing on MTPs placed in petri dishes or slide chambers were cultured untreated or exposed to antitumor drugs topotecan, mitoxantrone, or onconase for up to 4 days. Their attachment to- and growth on- MTPs was assessed by fluorescence microscopy and laser scanning cytometry (LSC) and compared with growth on the dish surface in the MTP neighborhood. The MTPs were fixed in ethanol, stained with propidium iodide (PI), and interrogated in flow in the instrument capable to rapidly (up to 103 MTPs/s) identify their ID signal and measure fluorescence. RESULTS: The cells plated on MTPs exhibited similar attachment properties to those plated in culture dishes. When measured by LSC, they had similar mitotic activity, growth rate, and cell cycle distributions as the cells adhering to the culture dish in the neighborhood of MTPs. The fluorescence intensity of MTPs provided information about the cell number per MTP, which made it possible to assess cell growth rate and monitor the cytostatic/cytotoxic effects of the tested drugs. CONCLUSIONS: The MTP-based system holds promise for the multiplexed cell assays in which numerous different cell lines can be screened for their growth rate or sensitivity while exposed to particular agents in the same vessel. Other advantages of the system are the rapidity of the screening and a very large number of ID codes. Because many cell lines/types can be assayed in a single dish, the system also offers cost savings on tissue culture reagents.

Adenocarcinoma↗

PubMed2006

Unambiguous prediction of human integrin transmembrane heterodimer interactions using only homologous sequences.

Part of the interaction between the alpha- and beta-subunits of integrins is known to take place at the transmembrane (TM) domain, where both heteromeric and homomeric aggregates have been reported in vivo and in vitro. In a recent computational study, totally independent from biochemical or biophysical data, we explored the plausibility of various TM homo-oligomers using evolutionary conservation data as a filter for non-native interactions. We showed that several homodimeric and homotrimeric interactions for alpha- and beta-chains are evolutionarily conserved. We report herein the results of the application of the same exhaustive approach to the integrin heterodimer. We have studied all known human TM integrin alphabeta pairs, and we show unambiguously that two models of interaction are evolutionarily conserved. These two models are consistent with those proposed previously based on mutagenesis and crosslinking. Comparison with previous experimental data strongly supports that a glycophorin A-like model is an intermediate form of interaction between the resting state and the active form, where chain separation occurs. Surprisingly, these two models are also conserved when considering most of the possible alphabeta pair combinations, suggesting that specific pairing of integrins is not determined by the TM domain, which has remained unchanged in spite of the variety of known integrin functions. This fact highlights a common ancestral mechanism for signal transduction that has remained through evolution. In a broader context, our results show that it is possible to obtain correct and detailed interactions of alpha-helical heterodimers with total independence of experimental data.

Amino Acid Sequence↗

PubMed2006

Expression of telomere-associated genes as prognostic markers for overall survival in patients with non-small cell lung cancer.

PURPOSE: Human telomeres, which are composed of long, repetitive sequences of TTAGGG and a variety of proteins, function as a protective structure capping the ends of chromosomes. Telomere dysfunction plays important roles in cancer initiation and progression. TRF1, TRF2, POT1, and RAP1 are four major telomere proteins that regulate telomere stability and telomere length. We hypothesized that the expression of these genes would have significant predictive value for cancer development and prognosis. EXPERIMENTAL DESIGN: We compared the mRNA expression level of TRF1, TRF2, POT1, and RAP1 between tumor and adjacent normal tissues from 148 patients with non-small cell lung cancer using real-time quantitative PCR. We then estimated the prognostic value of the mRNA expression of these genes in tumors. RESULTS: The expression level of TRF1 was significantly lower in tumor tissues than in adjacent normal tissues (P < 0.0001); no significant difference was found for TRF2, POT1, and RAP1. The expression of RAP1 gene in tumors was highly predictive of overall survival. In the Cox proportional hazards model, patients with higher RAP1 expression were associated with a significantly better survival [hazard ratio (HR), 0.47; 95% confidence interval (95% CI), 0.24-0.91]. This improved survival was more prominent in men (HR, 0.45; 95% CI, 0.22-0.996) and in ever smokers (HR, 0.50; 95% CI, 0.24-1.02). Kaplan-Meier survival curves showed that patients with higher RAP1 expression had significantly longer median survival than patients with lower expression (median = 51.21 versus 15.34 months, P < 0.0009). The expressions of TRF2 in tumor tissues were significantly correlated with tumor grades (P = 0.0114). CONCLUSIONS: RAP1 expression may be a useful biomarker of tumor progression and survival.

Aged↗

PubMed2006

Indirubin enhances tumor necrosis factor-induced apoptosis through modulation of nuclear factor-kappa B signaling pathway.

Although indirubin is known to exhibit anti-cancer and anti-inflammatory activities, very little is known about its mechanism of action. In this study, we investigated whether indirubin mediates its effects through interference with the NF-kappaB pathway. As examined by the DNA binding of NF-kappaB, we found that indirubin suppressed tumor necrosis factor (TNF)-induced NF-kappaB activation in a dose- and time-dependent manner. Indirubin also suppressed the NF-kappaB activation induced by various inflammatory agents and carcinogens. Further studies showed that indirubin blocked the phosphorylation and degradation of IkappaB alpha through the inhibition of activation of IkappaB alpha kinase and phosphorylation and nuclear translocation of p65. NF-kappaB reporter activity induced by TNFR1, TNF receptor-associated death domain, TRAF2, TAK1, NF-kappaB-inducing kinase, and IKKbeta was inhibited by indirubin but not that induced by p65 transfection. We also found that indirubin inhibited the expression of NF-kappaB-regulated gene products involved in antiapoptosis (IAP1, IAP2, Bcl-2, Bcl-xL, and TRAF1), proliferation (cyclin D1 and c-Myc), and invasion (COX-2 and MMP-9). This correlated with enhancement of the apoptosis induced by TNF and the chemotherapeutic agent taxol in human leukemic KBM-5 cells. Indirubin also suppressed cytokine-induced cellular invasion. Overall, our results indicate that anti-cancer and anti-inflammatory activities previously assigned to indirubin may be mediated in part through the suppression of the NF-kappaB activation pathway.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2006

A nonsynonymous single-nucleotide polymorphism in the PDZ-Rho guanine nucleotide exchange factor (Ser1416Gly) modulates the risk of lung cancer in Mexican Americans.

BACKGROUND: Based on in vitro studies, Rho guanine nucleotide exchange factors (RhoGEFs) are key regulators of mitogenic and transforming pathways. At least 1 family member, PDZ-RhoGEF, also integrates signaling between monomeric Rho G proteins and heterotrimeric G proteins through a so-called regulator of G-protein signaling (RGS) domain. Recently, the authors reported that 3 single-nucleotide polymorphisms (SNPs) in 2 members of the RGS family were associated with significant reductions in the risk of cancer. METHODS: For the current report, the authors studied the risk of lung cancer associated with a nonsynonymous SNP (rs868188; Ser1416Gly) in PDZ-RhoGEF in a large lung cancer case-control study of 2260 Caucasians and 369 Mexican Americans. RESULTS: Compared with individuals who had the wild-type genotype (AA), Mexican Americans with the variant genotypes (AG and GG) had a significantly reduced risk for lung cancer (odds ratio [OR], 0.57; 95% confidence interval [95%CI], 0.34-0.94). The protective effect appeared to be more evident in younger individuals (OR, 0.42; 95%CI, 0.20-0.91), men (OR, 0.36; 95%CI, 0.18-0.71), and ever smokers (OR, 0.50; 95%CI, 0.29-0.88). A joint effect was observed between Ser1416Gly and polymorphisms in 2 cell-cycle control genes: p53 (intron 3) and cyclin D1 (CCND1). Tallying the variant alleles of the 4 RGS gene SNPs, a gene-dosage effect was apparent. Compared with individuals who had < 3 variant alleles, patients with > or = 3 variant alleles had a 51% reduction in lung cancer risk (OR, 0.49; 95%CI, 0.28-0.88). CONCLUSIONS: To the authors' knowledge, this is the first epidemiological study to link PDZ-RhoGEF polymorphisms with cancer risk. The results suggest that there are interactions between RGS2, RGS6, and PDZ-RhoGEF and validate this family of proteins as key regulators of tumorigenesis.

Aged↗

PubMed2006

Model of a putative pore: the pentameric alpha-helical bundle of SARS coronavirus E protein in lipid bilayers.

The coronavirus responsible for the severe acute respiratory syndrome contains a small envelope protein, E, with putative involvement in host apoptosis and virus morphogenesis. To perform these functions, it has been suggested that protein E can form a membrane destabilizing transmembrane (TM) hairpin, or homooligomerize to form a TM pore. Indeed, in a recent study we reported that the alpha-helical putative transmembrane domain of E protein (ETM) forms several SDS-resistant TM interactions: a dimer, a trimer, and two pentameric forms. Further, these interactions were found to be evolutionarily conserved. Herein, we have studied multiple isotopically labeled ETM peptides reconstituted in model lipid bilayers, using the orientational parameters derived from infrared dichroic data. We show that the topology of ETM is consistent with a regular TM alpha-helix. Further, the orientational parameters obtained unequivocally correspond to a homopentameric model, by comparison with previous predictions. We have independently confirmed that the full polypeptide of E protein can also aggregate as pentamers after expression in Escherichia coli. This interaction must be stabilized, at least partially, at the TM domain. The model we report for this pentameric alpha-helical bundle may explain some of the permabilizing properties of protein E, and should be the basis of mutagenesis efforts in future functional studies.

Amino Acid Sequence↗

PubMed2006

Genome mining in Streptomyces coelicolor: molecular cloning and characterization of a new sesquiterpene synthase.

The terpene synthase encoded by the SCO5222 (SC7E4.19) gene of Streptomyces coelicolor was cloned by PCR and expressed in Escherichia coli as an N-terminal-His6-tag protein. Incubation of the recombinant protein, SCO5222p, with farnesyl diphosphate (1, FPP) in the presence of Mg(II) gave a new sesquiterpene, (+)-epi-isozizaene (2), whose structure and stereochemistry were determined by a combination of 1H, 13C, COSY, HMQC, HMBC, and NOESY NMR. The steady-state kinetic parameters were kcat 0.049 +/- 0.001 s-1 and a Km (FPP) of 147 +/- 14 nM. Individual incubations of recombinant epi-isozizaene synthase with [1,1-2H2]FPP (1a), (1R)-[1-2H]-FPP (1b), and (1S)-[1-2H]-FPP (1c) and NMR analysis of the resulting deuterated epi-isozizaenes supported an isomerization-cyclization-rearrangement mechanism involving the intermediacy of (3R)-nerolidyl diphosphate (3).

Alkyl and Aryl Transferases↗

PubMed2006

Stat3 activation of NF-{kappa}B p100 processing involves CBP/p300-mediated acetylation.

Activation of the noncanonical NF-kappaB signaling pathway involved in the proteolytic processing of NF-kappaB p100 to p52 is tightly regulated, and overproduction of p52 leads to lymphocyte hyperplasia and transformation. We have demonstrated that active but not latent Stat3, expressed in many types of human cancers involved in cell proliferation and survival, induces p100 processing to p52 by activation of IKKalpha and subsequent phosphorylation of p100. The Stat3-mediated p100 processing to p52 requires activation of Stat3 by the acetyltransferase activity of cAMP-response element-binding protein (CREB)-binding protein (CBP)/p300. A mutant of Stat3 defective in acetylation blocked Stat3-mediated p100 processing to p52 and acted as a dominant negative in blocking the production of p52. Furthermore, overexpression of p52 protected cells from apoptotic cell death. Thus, activation of the processing of p100 to p52 by Stat3 may represent one of the common pathways used by cancer cells to survive and escape therapy.

Acetylation↗

PubMed2006

Two types of transmembrane homomeric interactions in the integrin receptor family are evolutionarily conserved.

Integrins are heterodimers, but recent in vitro and in vivo experiments suggest that they are also able to associate through their transmembrane domains to form homomeric interactions. Two fundamental questions are the biological relevance of these aggregates and their form of interaction in the membrane domain. Although in vitro experiments have shown the involvement of a GxxxG-like motif, several crosslinking in vivo data are consistent with an almost opposite form of interaction between the transmembrane alpha-helices. In the present work, we have explored these two questions using molecular dynamics simulations for all available integrin types. We have tested the hypothesis that homomeric interactions are evolutionary conserved, and essential for the cell, using conservative substitutions to filter out nonnative interactions. Our results show that two models, one involving a GxxxG-like motif (model I) and an almost opposite form of interaction (model II) are conserved across all alpha and beta integrin types, both in homodimers and homotrimers, with different specificities. No conserved interaction was found for homotetramers. Our results are completely independent from experimental data, both during molecular dynamics simulations and in the selection of the correct models. We rationalize previous seemingly conflicting findings regarding the nature of integrin interhelical homomeric interactions.

Amino Acid Motifs↗

PubMed2006

Ubiquitination of RIP is required for tumor necrosis factor alpha-induced NF-kappaB activation.

Stimulation of cells with tumor necrosis factor (TNFalpha) triggers a recruitment of various signaling molecules, such as RIP, to the TNFalpha receptor 1 complex, leading to activation of NF-kappaB. Previous studies indicate that RIP plays an essential role for TNFalpha-induced NF-kappaB activation, but the molecular mechanism by which RIP mediates TNFalpha signals to activate NF-kappaB is not fully defined. Earlier studies suggest that RIP undergoes a ligand-dependent ubiquitination. However, it remains to be determined whether the ubiquitination of RIP is required for TNFalpha-induced NF-kappaB activation. In this study, we have identified Lys377 of RIP as the functional ubiquitination site, because mutating this residue to arginine completely abolished RIP-mediated NF-kappaB activation. The K377R mutation of RIP cannot undergo ligand-dependent ubiquitination and fails to recruit its downstream signaling components into the TNFalpha receptor 1 complex. Together, our studies provide the first genetic evidence that the ubiquitination of RIP is required for TNFalpha-induced NF-kappaB activation.

Amino Acid Sequence↗

PubMed2006

Overexpression of PKCalpha is required to impart estradiol inhibition and tamoxifen-resistance in a T47D human breast cancer tumor model.

We previously reported that stable overexpression of protein kinase C alpha (PKCalpha) in hormone responsive T47D:A18 breast cancer cells produces a hormone-independent/tamoxifen (TAM)-resistant and 17beta-estradiol (E2)-inhibitory phenotype in vivo. Furthermore, overexpression of PKCalpha in T47D:A18 cells also results in cross-upregulation of PKCs beta and delta. In this study, we further characterized the contribution of PKC isozymes alpha, beta and delta to this complex phenotype. To determine whether downregulation of PKCalpha is sufficient to restore the hormone-dependent phenotype in T47D:A18/PKCalpha cells, PKCalpha was selectively knocked down using short hairpin RNA (shRNA). To determine the contribution of PKCbeta or delta to the hormone-independent/TAM-resistant and E2-inhibitory phenotype, stable T47D:A18/PKCbeta and T47D:A18/PKCdelta clones were established. Downregulation of PKCalpha by shRNA in T47D:A18/PKCalpha20 cells also resulted in reduced PKCbeta protein expression in vitro. Tumors established from a T47D:A18/PKCalpha/shRNA stable clone exhibit 50% reduction of PKCalpha protein without concomitant reduction in PKCbeta, and exhibit partial reversal of the TAM-resistant and E2-inhibitory phenotype in vivo. Furthermore, stable overexpression of neither PKCbeta nor PKCdelta in T47D:A18 cells are sufficient to produce hormone-independent growth in vitro or in vivo, nor TAM-resistant and E2-inhibited growth in vivo. Taken together, these results suggest that PKCalpha is required to impart the TAM-resistant and E2-inhibitory phenotype in vivo.

Animals↗