RESUMEN
BACKGROUND: Aberrant PI3K/AKT signaling in BRAF-mutant cancers contributes to resistance to BRAF inhibitors. The authors examined dual MAPK and PI3K pathway inhibition in patients who had BRAF-mutated solid tumors (ClinicalTrials.gov identifier NCT01902173). METHODS: Patients with BRAF V600E/V600K-mutant solid tumors received oral dabrafenib at 150 mg twice daily with dose escalation of oral uprosertib starting at 50 mg daily, or, in the triplet cohorts, with dose escalation of both oral trametinib starting at 1.5 mg daily and oral uprosertib starting at 25 mg daily. Dose-limiting toxicities (DLTs) were assessed within the first 56 days of treatment. Radiographic responses were assessed at 8-week intervals. RESULTS: Twenty-seven patients (22 evaluable) were enrolled in parallel doublet and triplet cohorts. No DLTs were observed in the doublet cohorts (N = 7). One patient had a DLT at the maximum administered dose of triplet therapy (dabrafenib 150 mg twice daily and trametinib 2 mg daily plus uprosertib 75 mg daily). Three patients in the doublet cohorts had partial responses (including one who had BRAF inhibitor-resistant melanoma). Two patients in the triplet cohorts had a partial response, and one patient had an unconfirmed partial response. Pharmacokinetic data suggested reduced dabrafenib and dabrafenib metabolite exposure in patients who were also exposed to both trametinib and uprosertib, but not in whose who were exposed to uprosertib without trametinib. CONCLUSIONS: Concomitant inhibition of both the MAPK and PI3K-AKT pathways for the treatment of BRAF-mutated cancers was well tolerated, leading to objective responses, but higher level drug-drug interactions affected exposure to dabrafenib and its metabolites.
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Protocolos de Quimioterapia Combinada Antineoplásica , Imidazoles , Mutación , Neoplasias , Oximas , Inhibidores de Proteínas Quinasas , Proteínas Proto-Oncogénicas B-raf , Proteínas Proto-Oncogénicas c-akt , Piridonas , Pirimidinonas , Humanos , Proteínas Proto-Oncogénicas B-raf/genética , Proteínas Proto-Oncogénicas B-raf/antagonistas & inhibidores , Femenino , Masculino , Persona de Mediana Edad , Anciano , Adulto , Piridonas/administración & dosificación , Piridonas/efectos adversos , Pirimidinonas/administración & dosificación , Pirimidinonas/efectos adversos , Pirimidinonas/uso terapéutico , Imidazoles/administración & dosificación , Imidazoles/uso terapéutico , Imidazoles/efectos adversos , Imidazoles/farmacocinética , Proteínas Proto-Oncogénicas c-akt/metabolismo , Oximas/administración & dosificación , Oximas/efectos adversos , Oximas/uso terapéutico , Neoplasias/tratamiento farmacológico , Neoplasias/genética , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Inhibidores de Proteínas Quinasas/administración & dosificación , Inhibidores de Proteínas Quinasas/efectos adversos , Inhibidores de Proteínas Quinasas/uso terapéutico , Anciano de 80 o más Años , Terapia Molecular DirigidaRESUMEN
Blocking cancer genomic instability may prevent tumor diversification and escape from therapies. We show that, after MAPK inhibitor (MAPKi) therapy in patients and mice bearing patient-derived xenografts (PDX), acquired resistant genomes of metastatic cutaneous melanoma specifically amplify resistance-driver, nonhomologous end-joining (NHEJ), and homologous recombination repair (HRR) genes via complex genomic rearrangements (CGR) and extrachromosomal DNAs (ecDNA). Almost all sensitive and acquired-resistant genomes harbor pervasive chromothriptic regions with disproportionately high mutational burdens and significant overlaps with ecDNA and CGR spans. Recurrently, somatic mutations within ecDNA and CGR amplicons enrich for HRR signatures, particularly within acquired resistant tumors. Regardless of sensitivity or resistance, breakpoint-junctional sequence analysis suggests NHEJ as critical to double-stranded DNA break repair underlying CGR and ecDNA formation. In human melanoma cell lines and PDXs, NHEJ targeting by a DNA-PKCS inhibitor prevents/delays acquired MAPKi resistance by reducing the size of ecDNAs and CGRs early on combination treatment. Thus, targeting the causes of genomic instability prevents acquired resistance. SIGNIFICANCE: Acquired resistance often results in heterogeneous, redundant survival mechanisms, which challenge strategies aimed at reversing resistance. Acquired-resistant melanomas recurrently evolve resistance-driving and resistance-specific amplicons via ecDNAs and CGRs, thereby nominating chromothripsis-ecDNA-CGR biogenesis as a resistance-preventive target. Specifically, targeting DNA-PKCS/NHEJ prevents resistance by suppressing ecDNA/CGR rearrangements in MAPKi-treated melanomas. This article is highlighted in the In This Issue feature, p. 799.
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Melanoma , Neoplasias Cutáneas , Humanos , Animales , Ratones , Melanoma/tratamiento farmacológico , Melanoma/genética , Melanoma/metabolismo , Neoplasias Cutáneas/tratamiento farmacológico , Neoplasias Cutáneas/genética , Línea Celular , Inestabilidad Genómica , ADNRESUMEN
Metastasis and failure of present-day therapies represent the most common causes of mortality in patients with cutaneous melanoma. To identify the underlying genetic and transcriptomic landscapes, in this study we analyzed multi-organ metastases and tumor-adjacent tissues from 11 rapid autopsies after treatment with MAPK inhibitor (MAPKi) and/or immune checkpoint blockade (ICB) and death due to acquired resistance. Either treatment elicits shared genetic alterations that suggest immune-evasive, cross-therapy resistance mechanisms. Large, non-clustered deletions, inversions and inter-chromosomal translocations dominate rearrangements. Analyzing data from separate melanoma cohorts including 345 therapy-naive patients and 35 patients with patient-matched pre-treatment and post-acquired resistance tumor samples, we performed cross-cohort analyses to identify MAPKi and ICB as respective contributors to gene amplifications and deletions enriched in autopsy versus therapy-naive tumors. In the autopsy cohort, private/late mutations and structural variants display shifted mutational and rearrangement signatures, with MAPKi specifically selecting for signatures of defective homologous-recombination, mismatch and base-excision repair. Transcriptomic signatures and crosstalks with tumor-adjacent macroenvironments nominated organ-specific adaptive pathways. An immune-desert, CD8+-macrophage-biased archetype, T-cell exhaustion and type-2 immunity characterized the immune contexture. This multi-organ analysis of therapy-resistant melanoma presents preliminary insights with potential to improve therapeutic strategies.
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Melanoma , Neoplasias Cutáneas , Humanos , Melanoma/tratamiento farmacológico , Melanoma/genética , Melanoma/patología , Neoplasias Cutáneas/tratamiento farmacológico , Neoplasias Cutáneas/genética , Resistencia a Antineoplásicos/genética , Transcriptoma/genética , Perfilación de la Expresión GénicaRESUMEN
MAPK inhibitor (MAPKi) therapy in melanoma leads to the accumulation of tumor-surface PD-L1/L2, which may evade antitumor immunity and accelerate acquired resistance. Here, we discover that the E3 ligase ITCH binds, ubiquitinates, and downregulates tumor-surface PD-L1/L2 in MAPKi-treated human melanoma cells, thereby promoting T-cell activation. During MAPKi therapy in vivo, melanoma cell-intrinsic ITCH knockdown induced tumor-surface PD-L1, reduced intratumoral cytolytic CD8+ T cells, and accelerated acquired resistance only in immune-competent mice. Conversely, tumor cell-intrinsic ITCH overexpression reduced MAPKi-elicited PD-L1 accumulation, augmented intratumoral cytolytic CD8+ T cells, and suppressed acquired resistance in BrafV600MUT, NrasMUT, or Nf1MUT melanoma and KrasMUT-driven cancers. CD8+ T-cell depletion and tumor cell-intrinsic PD-L1 overexpression nullified the phenotype of ITCH overexpression, thereby supporting an in vivo ITCH-PD-L1-T-cell regulatory axis. Moreover, we identify a small-molecular ITCH activator that suppresses acquired MAPKi resistance in vivo. Thus, MAPKi-induced PD-L1 accelerates resistance, and a PD-L1-degrading ITCH activator prolongs antitumor response. SIGNIFICANCE: MAPKi induces tumor cell-surface PD-L1 accumulation, which promotes immune evasion and therapy resistance. ITCH degrades PD-L1, optimizing antitumor T-cell immunity. We propose degrading tumor cell-surface PD-L1 and/or activating tumor-intrinsic ITCH as strategies to overcome MAPKi resistance. This article is highlighted in the In This Issue feature, p. 1825.
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Antígeno B7-H1 , Melanoma , Proteínas Quinasas Activadas por Mitógenos , Proteínas Represoras , Ubiquitina-Proteína Ligasas , Animales , Linfocitos T CD8-positivos , Línea Celular Tumoral , Resistencia a Antineoplásicos/genética , Humanos , Melanoma/genética , Ratones , Proteínas Quinasas Activadas por Mitógenos/antagonistas & inhibidores , Proteínas Represoras/genética , Ubiquitina-Proteína Ligasas/genéticaRESUMEN
Extrachromosomal DNA (ecDNA) is a common mode of oncogene amplification but is challenging to analyze. Here, we adapt CRISPR-CATCH, in vitro CRISPR-Cas9 treatment and pulsed field gel electrophoresis of agarose-entrapped genomic DNA, previously developed for bacterial chromosome segments, to isolate megabase-sized human ecDNAs. We demonstrate strong enrichment of ecDNA molecules containing EGFR, FGFR2 and MYC from human cancer cells and NRAS ecDNA from human metastatic melanoma with acquired therapeutic resistance. Targeted enrichment of ecDNA versus chromosomal DNA enabled phasing of genetic variants, identified the presence of an EGFRvIII mutation exclusively on ecDNAs and supported an excision model of ecDNA genesis in a glioblastoma model. CRISPR-CATCH followed by nanopore sequencing enabled single-molecule ecDNA methylation profiling and revealed hypomethylation of the EGFR promoter on ecDNAs. We distinguished heterogeneous ecDNA species within the same sample by size and sequence with base-pair resolution and discovered functionally specialized ecDNAs that amplify select enhancers or oncogene-coding sequences.
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Glioblastoma , Neoplasias , Humanos , Oncogenes , ADN/genética , Neoplasias/genética , Neoplasias/patología , Glioblastoma/genética , Receptores ErbB/genéticaRESUMEN
Focal amplifications (FA) can mediate targeted therapy resistance in cancer. Understanding the structure and dynamics of FAs is critical for designing treatments that overcome plasticity-mediated resistance. We developed a melanoma model of dual MAPK inhibitor (MAPKi) resistance that bears BRAFV600 amplifications through either extrachromosomal DNA (ecDNA)/double minutes (DM) or intrachromosomal homogenously staining regions (HSR). Cells harboring BRAFV600E FAs displayed mode switching between DMs and HSRs, from both de novo genetic changes and selection of preexisting subpopulations. Plasticity is not exclusive to ecDNAs, as cells harboring HSRs exhibit drug addiction-driven structural loss of BRAF amplicons upon dose reduction. FA mechanisms can couple with kinase domain duplications and alternative splicing to enhance resistance. Drug-responsive amplicon plasticity is observed in the clinic and can involve other MAPK pathway genes, such as RAF1 and NRAS. BRAF FA-mediated dual MAPKi-resistant cells are more sensitive to proferroptotic drugs, extending the spectrum of ferroptosis sensitivity in MAPKi resistance beyond cases of dedifferentiation. SIGNIFICANCE: Understanding the structure and dynamics of oncogene amplifications is critical for overcoming tumor relapse. BRAF amplifications are highly plastic under MAPKi dosage challenges in melanoma, through involvement of de novo genomic alterations, even in the HSR mode. Moreover, BRAF FA-driven, dual MAPKi-resistant cells extend the spectrum of resistance-linked ferroptosis sensitivity. This article is highlighted in the In This Issue feature, p. 873.
Asunto(s)
Melanoma , Proteínas Proto-Oncogénicas B-raf , Línea Celular Tumoral , Resistencia a Antineoplásicos , Humanos , Melanoma/tratamiento farmacológico , Melanoma/genética , Melanoma/patología , Mutación , Recurrencia Local de Neoplasia/tratamiento farmacológico , Oncogenes , Inhibidores de Proteínas Quinasas/farmacología , Inhibidores de Proteínas Quinasas/uso terapéutico , Proteínas Proto-Oncogénicas B-raf/genética , Proteínas Proto-Oncogénicas B-raf/metabolismoRESUMEN
Rationally sequencing and combining PD-1/L1-and MAPK-targeted therapies may overcome innate and acquired resistance. Since increased clinical benefit of MAPK inhibitors (MAPKi) is associated with previous immune checkpoint therapy, we compare the efficacies of sequential and/or combinatorial regimens in subcutaneous murine models of melanoma driven by BrafV600, Nras, or Nf1 mutations as well as colorectal and pancreatic carcinoma driven by KrasG12C. Anti-PD-1/L1 lead-in preceding MAPKi combination optimizes response durability by promoting pro-inflammatory polarization of macrophages and clonal expansion of interferon-γhi, and CD8+ cytotoxic and proliferative (versus CD4+ regulatory) T cells that highly express activation genes. Since therapeutic resistance of melanoma brain metastasis (MBM) limits patient survival, we demonstrate that sequencing anti-PD-1/L1 therapy before MAPKi combination suppresses MBM and improves mouse survival with robust T cell clonal expansion in both intracranial and extracranial metastatic sites. We propose clinically testing brief anti-PD-1/L1 (± anti-CTLA-4) dosing before MAPKi co-treatment to suppress therapeutic resistance.
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Inhibidores de Puntos de Control Inmunológico/uso terapéutico , Inmunoterapia/métodos , Quinasas de Proteína Quinasa Activadas por Mitógenos/antagonistas & inhibidores , Neoplasias/tratamiento farmacológico , Animales , Humanos , Inhibidores de Puntos de Control Inmunológico/farmacología , RatonesRESUMEN
Neoadjuvant PD-1 blockade may be efficacious in some individuals with high-risk, resectable oral cavity head and neck cancer. To explore correlates of response patterns to neoadjuvant nivolumab treatment and post-surgical recurrences, we analyzed longitudinal tumor and blood samples in a cohort of 12 individuals displaying 33% responsiveness. Pretreatment tumor-based detection of FLT4 mutations and PTEN signature enrichment favors response, and high tumor mutational burden improves recurrence-free survival. In contrast, preexisting and/or acquired mutations (in CDKN2A, YAP1, or JAK2) correlate with innate resistance and/or tumor recurrence. Immunologically, tumor response after therapy entails T cell receptor repertoire diversification in peripheral blood and intratumoral expansion of preexisting T cell clones. A high ratio of regulatory T to T helper 17 cells in pretreatment blood predicts low T cell receptor repertoire diversity in pretreatment blood, a low cytolytic T cell signature in pretreatment tumors, and innate resistance. Our study provides a molecular framework to advance neoadjuvant anti-PD-1 therapy for individuals with resectable head and neck cancer.
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Carcinoma de Células Escamosas/tratamiento farmacológico , Neoplasias de la Boca/tratamiento farmacológico , Recurrencia Local de Neoplasia/tratamiento farmacológico , Nivolumab/uso terapéutico , Receptor de Muerte Celular Programada 1/genética , Receptor 3 de Factores de Crecimiento Endotelial Vascular/genética , Antineoplásicos Inmunológicos/uso terapéutico , Carcinoma de Células Escamosas/genética , Carcinoma de Células Escamosas/inmunología , Carcinoma de Células Escamosas/cirugía , Inhibidor p16 de la Quinasa Dependiente de Ciclina/genética , Inhibidor p16 de la Quinasa Dependiente de Ciclina/inmunología , Perfilación de la Expresión Génica , Regulación Neoplásica de la Expresión Génica , Humanos , Inhibidores de Puntos de Control Inmunológico/uso terapéutico , Janus Quinasa 2/genética , Janus Quinasa 2/inmunología , Neoplasias de la Boca/genética , Neoplasias de la Boca/inmunología , Neoplasias de la Boca/cirugía , Mutación , Terapia Neoadyuvante/métodos , Recurrencia Local de Neoplasia/genética , Recurrencia Local de Neoplasia/inmunología , Recurrencia Local de Neoplasia/cirugía , Fosfohidrolasa PTEN/genética , Fosfohidrolasa PTEN/inmunología , Receptor de Muerte Celular Programada 1/antagonistas & inhibidores , Receptor de Muerte Celular Programada 1/inmunología , Receptores de Antígenos de Linfocitos T alfa-beta/genética , Receptores de Antígenos de Linfocitos T alfa-beta/inmunología , Análisis de Supervivencia , Linfocitos T Reguladores/efectos de los fármacos , Linfocitos T Reguladores/inmunología , Linfocitos T Reguladores/patología , Células Th17/efectos de los fármacos , Células Th17/inmunología , Células Th17/patología , Resultado del Tratamiento , Receptor 3 de Factores de Crecimiento Endotelial Vascular/inmunología , Proteínas Señalizadoras YAP/genética , Proteínas Señalizadoras YAP/inmunologíaRESUMEN
Oral cavity squamous cell carcinoma (OCSCC) is a prevalent surgically treated subset of head and neck cancer with frequent recurrence and poor survival. Immunotherapy has demonstrated efficacy in recurrent/metastatic head and neck cancer. However, whether antitumor responses could be fostered by neoadjuvant presurgical immunotherapy remains unclear. Using a Simon's two-stage design, we present results of a single-arm phase-II trial where 12 patients with stage II-IVA OCSCC received 3 to 4 biweekly doses of 3 mg/kg nivolumab followed by definitive surgical resection with curative intent. Presurgical nivolumab therapy in this cohort shows an overall response rate of 33% (n = 4 patients; 95% CI: 12%-53%). With a median follow up of 2.23 years, 10 out of 12 treated patients remain alive. Neoadjuvant nivolumab is safe, well-tolerated, and is not associated with delays in definitive surgical treatment in this study. This work demonstrates feasibility and safety for incorporation of nivolumab in the neoadjuvant setting for OCSCC (ClinicalTrials.gov: NCT03021993).
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Carcinoma de Células Escamosas/tratamiento farmacológico , Neoplasias de la Boca/tratamiento farmacológico , Recurrencia Local de Neoplasia/tratamiento farmacológico , Nivolumab/uso terapéutico , Receptor de Muerte Celular Programada 1/genética , Anciano , Antineoplásicos Inmunológicos/uso terapéutico , Carcinoma de Células Escamosas/inmunología , Carcinoma de Células Escamosas/mortalidad , Carcinoma de Células Escamosas/cirugía , Estudios de Cohortes , Femenino , Regulación Neoplásica de la Expresión Génica , Humanos , Inhibidores de Puntos de Control Inmunológico/uso terapéutico , Masculino , Persona de Mediana Edad , Neoplasias de la Boca/inmunología , Neoplasias de la Boca/mortalidad , Neoplasias de la Boca/cirugía , Terapia Neoadyuvante/métodos , Recurrencia Local de Neoplasia/inmunología , Recurrencia Local de Neoplasia/mortalidad , Recurrencia Local de Neoplasia/cirugía , Estadificación de Neoplasias , Receptor de Muerte Celular Programada 1/antagonistas & inhibidores , Receptor de Muerte Celular Programada 1/inmunología , Análisis de Supervivencia , Resultado del TratamientoRESUMEN
MAPK targeting in cancer often fails due to MAPK reactivation. MEK inhibitor (MEKi) monotherapy provides limited clinical benefits but may serve as a foundation for combination therapies. Here, we showed that combining a type II RAF inhibitor (RAFi) with an allosteric MEKi durably prevents and overcomes acquired resistance among cancers with KRAS, NRAS, NF1, BRAF non-V600, and BRAF V600 mutations. Tumor cell-intrinsically, type II RAFi plus MEKi sequester MEK in RAF complexes, reduce MEK/MEK dimerization, and uncouple MEK from ERK in acquired-resistant tumor subpopulations. Immunologically, this combination expands memory and activated/exhausted CD8+ T cells, and durable tumor regression elicited by this combination requires CD8+ T cells, which can be reinvigorated by anti-PD-L1 therapy. Whereas MEKi reduces dominant intratumoral T-cell clones, type II RAFi cotreatment reverses this effect and promotes T-cell clonotypic expansion. These findings rationalize the clinical development of type II RAFi plus MEKi and their further combination with PD-1/L1-targeted therapy. SIGNIFICANCE: Type I RAFi + MEKi are indicated only in certain BRAF V600MUT cancers. In contrast, type II RAFi + MEKi are durably active against acquired MEKi resistance across broad cancer indications, which reveals exquisite MAPK addiction. Allosteric modulation of MAPK protein/protein interactions and temporal preservation of intratumoral CD8+ T cells are mechanisms that may be further exploited.This article is highlighted in the In This Issue feature, p. 521.
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Resistencia a Antineoplásicos , Quinasas MAP Reguladas por Señal Extracelular/antagonistas & inhibidores , Quinasas de Proteína Quinasa Activadas por Mitógenos/antagonistas & inhibidores , Inhibidores de Proteínas Quinasas/farmacología , Linfocitos T/efectos de los fármacos , Linfocitos T/inmunología , Linfocitos T/metabolismo , Animales , Protocolos de Quimioterapia Combinada Antineoplásica/efectos adversos , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapéutico , Biomarcadores de Tumor/genética , Biomarcadores de Tumor/metabolismo , Línea Celular Tumoral , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Resistencia a Antineoplásicos/efectos de los fármacos , GTP Fosfohidrolasas/genética , GTP Fosfohidrolasas/metabolismo , Humanos , Inmunidad Celular/efectos de los fármacos , Linfocitos Infiltrantes de Tumor/efectos de los fármacos , Linfocitos Infiltrantes de Tumor/inmunología , Linfocitos Infiltrantes de Tumor/metabolismo , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Ratones , Mutación , Neoplasias/tratamiento farmacológico , Neoplasias/etiología , Neoplasias/metabolismo , Neoplasias/patología , Unión Proteica , Estabilidad Proteica , Resultado del Tratamiento , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
Mass spectrometry (MS) and ion mobility with electrospray ionization (ESI) have the capability to measure and detect large noncovalent protein-ligand and protein-protein complexes. Using an ion mobility method of gas-phase electrophoretic mobility molecular analysis (GEMMA), protein particles representing a range of sizes can be separated by their electrophoretic mobility in air. Highly charged particles produced from a protein complex solution using electrospray can be manipulated to produce singly charged ions, which can be separated and quantified by their electrophoretic mobility. Results from ESI-GEMMA analysis from our laboratory and others were compared with other experimental and theoretically determined parameters, such as molecular mass and cryoelectron microscopy and X-ray crystal structure dimensions. There is a strong correlation between the electrophoretic mobility diameter determined from GEMMA analysis and the molecular mass for protein complexes up to 12 MDa, including the 93 kDa enolase dimer, the 480 kDa ferritin 24-mer complex, the 4.6 MDa cowpea chlorotic mottle virus (CCMV), and the 9 MDa MVP-vault assembly. ESI-GEMMA is used to differentiate a number of similarly sized vault complexes that are composed of different N-terminal protein tags on the MVP subunit. The average effective density of the proteins and protein complexes studied was 0.6 g/cm(3). Moreover, there is evidence that proteins and protein complexes collapse or become more compact in the gas phase in the absence of water.
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Modelos Químicos , Modelos Moleculares , Fosfopiruvato Hidratasa/química , Fosfopiruvato Hidratasa/ultraestructura , Espectrometría de Masa por Ionización de Electrospray/métodos , Simulación por Computador , Dimerización , Electroforesis/métodos , Peso Molecular , Complejos Multiproteicos/química , Complejos Multiproteicos/ultraestructuraRESUMEN
Autoantibody (autoAb) response is an important arm of endogenously arising anti-tumor immune responses, and has received new attention as a cancer biomarker with the recent success of immune check-point inhibitor therapy. Our laboratory has been focusing on measuring autoAb against B-cell epitopes in order to bypass the necessity to purify a panel of recombinant proteins. In order to optimize peptide-based autoAb measurement and to increase sensitivities to cover more patients, we developed a new approach of using mixed peptides to conjugate on the same microsphere and compared its results with the use of a dominant peptide epitope using Luminex microbead-based multiplex assays. The peptide epitopes of two cancer/germline antigens, New York esophageal cancer antigen-1 (NY-ESO-1) and X antigen family member-1b (XAGE-1b), and cancer/stem cell antigen, sex determining region Y-box-2 (SOX2), were used as prototypes in this study. Our results indicate that using mixed peptides of B-cell epitopes improves the sensitivity of detecting more patients with autoAb responses. Thus, when the full-length protein is not available for conjugating onto microspheres, a mixture of B-cell epitopes is the method of choice for using Luminex multiplex assay to detect autoAb response in cancer patients.
RESUMEN
Human sex determining region Y-box 2 (SOX2) is an important transcriptional factor involved in the pluripotency and stemness of human embryonic stem cells. SOX2 plays important roles in maintaining cancer stem cell activities of melanoma and cancers of the brain, prostate, breast, and lung. SOX2 is also a lineage survival oncogene for squamous cell carcinoma of the lung and esophagus. Spontaneous cellular and humoral immune responses against SOX2 present in cancer patients classify it as a tumor-associated antigen (TAA) shared by lung cancer, glioblastoma, and prostate cancer among others. In this study, B-cell epitopes were predicted using computer-assisted algorithms. Synthetic peptides based on the prediction were screened for recognition by serum samples from cancer patients using ELISA. Two dominant B-cell epitopes, SOX2:52-87 and SOX2:98-124 were identified. Prostate cancer, glioblastoma and lung cancer serum samples that recognized the above SOX2 epitopes also recognized the full-length protein based on Western blot. These B-cell epitopes may be used in assessing humoral immune responses against SOX2 in cancer immunotherapy and stem cell-related transplantation.
RESUMEN
The addition of m-nitrobenzyl alcohol (m-NBA) was shown previously (Lomeli et al., J. Am. Soc. Mass Spectrom. 2009, 20, 593-596) to enhance multiple charging of native proteins and noncovalent protein complexes in electrospray ionization (ESI) mass spectra. Additional new reagents have been found to "supercharge" proteins from nondenaturing solutions; several of these reagents are shown to be more effective than m-NBA for increasing positive charging. Using the myoglobin protein-protoporphyrin IX (heme) complex, the following reagents were shown to increase ESI charging: benzyl alcohol, m-nitroacetophenone, m-nitrobenzonitrile, o-NBA, m-NBA, p-NBA, m-nitrophenyl ethanol, sulfolane (tetramethylene sulfone), and m-(trifluoromethyl)-benzyl alcohol. Based on average charge state, sulfolane displayed a greater charge increase (61%) than m-NBA (21%) for myoglobin in aqueous solutions. The reagents that promote higher ESI charging appear to have low solution-phase basicities and relatively low gas-phase basicities, and are less volatile than water. Another feature of mass spectra from some of the active reagents is that adducts are present on higher charge states, suggesting that a mechanism by which proteins acquire additional charge involves direct interaction with the reagent, in addition to other factors such as surface tension and protein denaturation.
Asunto(s)
Proteínas/química , Espectrometría de Masa por Ionización de Electrospray/métodos , Tiofenos , Animales , Caballos , Indicadores y Reactivos/química , Mioglobina/química , Conformación Proteica , Electricidad Estática , Tiofenos/químicaRESUMEN
Increased multiple charging of native proteins and noncovalent protein complexes is observed in electrospray ionization (ESI) mass spectra obtained from nondenaturing protein solutions containing up to 1% (vol/vol) m-nitrobenzyl alcohol (m-NBA). The increases in charge ranged from 8% for the 690 kDa alpha(7)beta(7)beta(7)alpha(7) 20S proteasome complex to 48% additional charge for the zinc-bound 29 kDa carbonic anhydrase-II protein. No dissociation of the noncovalently bound ligands/subunits was observed upon the addition of m-NBA. It is not clear if the enhanced charging is related to altered surface tension as proposed in the "supercharging" model of Iavarone and Williams (Iavarone, A. T.; Williams, E. R. J. Am. Chem. Soc.2003, 125, 2319-2327). However, more highly charged noncovalent protein complexes have utility in relaxing slightly the mass-to-charge (m/z) requirements of the mass spectrometer for detection and will be effective for enhancing the efficiency for tandem mass spectrometry studies of protein complexes.