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BACKGROUND: The role of MET alterations in non-small cell lung cancer (NSCLC) is increasing and several targeted agents are under evaluation. MET exon 14 skipping mutations and MET amplifications are associated with potential sensitivity to MET inhibition, though resistance mechanisms are emerging. In MET addicted cells, MET inhibition leads to activation of proviral integration site for Moloney murine leukemia virus-1 (PIM1). PIM1 and proto-oncogene tyrosine-protein kinase Src (SRC) can regulate the expression of receptor tyrosine kinases (RTKs), potentially inducing resistance to MET inhibition through cross-activation. METHODS: We evaluated the activity of class I-II MET inhibitors, the SRC inhibitor dasatinib, and pan-PIM inhibitors in four MET addicted cell lines. We assessed the effect of the dual MET/PIM and MET/SRC inhibition on cell viability and at the protein level. We evaluated RNA expression profiles of the cell lines. Advanced NSCLCs were also screened for MET alterations. RESULTS: All cell lines were sensitive to class I-II MET inhibitors. All cell lines were resistant to single PIM and SRC inhibition. Dual MET/PIM inhibition was synergistic or additive in MET amplified cell lines and dual MET/SRC inhibition was highly synergistic in all MET addicted cell lines. The addition of an SRC inhibitor partially prevents the RTKs cross-activation. MET alterations were found in 9 out of 97 evaluable samples (9.3%); median overall survival in MET altered patients was 5 months (95% CI, 3 m-NA). CONCLUSIONS: We identified a potential role of PIM inhibition in MET amplified tumors and of SRC inhibition in MET addicted tumors. Potential applications of this new treatment strategy warrant further evaluation.
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BACKGROUND: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) induce significant responses in EGFR-mutation positive non-small cell lung cancer (NSCLC). However, universal progression is observed. METHODS: The effect of the anti-rheumatoid agent, auranofin, a selective inhibitor of oncogenic protein kinase C iota (PKCι) signaling and IPA-3, a non-ATP competitive p21-activated kinase 1 (PAK1) inhibitor in treatment-naïve and EGFR TKI-resistant EGFR-mutation positive NSCLC cell lines was investigated. PC9 and HCC827 cells were used. The four EGFR-TKI resistant cell lines were established from PC9. Cell viability assays, drug combination studies, and western blotting were performed. The combination index, and RTK or non-RTK expression were performed. RESULTS: The combination of IPA-3 and auranofin was highly synergistic in all 6 cell lines (combination indexes ranged from 0.37-0.62). The activities on EGFR, CDCP1, AXL, MET, and downstream effector pathways, including PAK1, PKCι, ERK, AKT, STAT3, Src, and YAP1 were abrogated. CONCLUSIONS: The combination of auranofin with IPA-3 could be a potential therapy for EGFR-mutation positive NSCLC resistant to EGFR TKIs. Auranofin with IPA-3 could become a therapeutic solution for EGFR-mutation positive NSCLC patients resistant to EGFR TKIs.
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Monotherapy with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) still leads to incomplete responses in most EGFR-mutation positive non-small cell lung cancer (NSCLC) patients, often due to acquired resistance through activation of parallel compensatory pathways. We have previously shown that co-targeting EGFR, signal transducer and activator of transcription 3 (STAT3), and Src-yes-associated protein 1 (YAP1) was highly synergistic in vitro and in vivo. In the present study, we treated EGFR-mutation positive cell lines with the combination of osimertinib plus a natural compound, pterostilbene, which has been reported to abrogate Src and STAT3 activation. Methods: Cell viability assays and immunoblotting were performed to reveal the mechanisms of action of pterostilbene, osimertinib and pterostilbene plus osimertinib in five EGFR-mutation positive NSCLC and one triple negative breast cancer (TNBC) cell lines. Results: Osimertinib plus pterostilbene yielded synergistic effects in all EGFR-mutation positive NSCLC cell lines investigated. Surprisingly, pterostilbene alone did not inhibit, nor downregulate Src phosphorylation in the EGFR-mutation positive NSCLC cell lines or the TNBC cell line, MDA-MB-231. However, the double combination of osimertinib plus pterostilbene reversed the osimertinib-induced STAT3, YAP1, and CUB domain-containing protein-1 (CDCP1) phosphorylation and slightly suppressed Src phosphorylation in PC9 and H1975 cells. Conclusion: The results of this study indicate that pterostilbene may be used to abrogate the activated resistance pathways of single osimertinib treatment in EGFR-mutation positive NSCLC. Future studies should focus on in vivo translation and confirmation of these results.
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Acrilamidas/uso terapéutico , Compuestos de Anilina/uso terapéutico , Antineoplásicos/uso terapéutico , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Estilbenos/uso terapéutico , Neoplasias de la Mama Triple Negativas/tratamiento farmacológico , Proteínas Adaptadoras Transductoras de Señales/antagonistas & inhibidores , Proteínas Adaptadoras Transductoras de Señales/genética , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Antígenos de Neoplasias/metabolismo , Carcinoma de Pulmón de Células no Pequeñas/genética , Carcinoma de Pulmón de Células no Pequeñas/patología , Moléculas de Adhesión Celular/metabolismo , Línea Celular Tumoral , Resistencia a Antineoplásicos , Sinergismo Farmacológico , Receptores ErbB/antagonistas & inhibidores , Receptores ErbB/genética , Humanos , Fosforilación , Factor de Transcripción STAT3/antagonistas & inhibidores , Factor de Transcripción STAT3/metabolismo , Factores de Transcripción/antagonistas & inhibidores , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Neoplasias de la Mama Triple Negativas/genética , Neoplasias de la Mama Triple Negativas/patología , Proteínas Señalizadoras YAPRESUMEN
INTRODUCTION: p21-activated kinase 1 (PAK1) stimulates growth and metastasis in non-small cell lung cancer (NSCLC). Protein kinase C iota (PKCι) is an enzyme highly expressed in NSCLC, regulating PAK1 signaling. In the present study we explored whether the PKCι-PAK1 signaling pathway approach can be an efficient target in different types of NSCLC cell and mouse models. METHODS: The effect of IPA-3 (PAK1 inhibitor) plus auranofin (PKCι inhibitor) combination was evaluated by cell viability assay, colony formation and western blotting assay, using three types of NSCLC cell lines: EGFR or KRAS mutant adenocarcinoma and squamous cell carcinoma with PAK1 amplification. In addition, for clinical availability, screening for new PAK1 inhibitors was carried out and the compound OTSSP167 was evaluated in combination with auranofin in cell and mice models. RESULTS: The combination of IPA-3 or OTSSP167 plus auranofin showed high synergism for inhibiting cell viability and colony formation in three cell lines. Mechanistic characterization revealed that this drug combination abrogated expression and activation of membrane receptors and downstream signaling proteins crucial in lung cancer: EGFR, MET, PAK1, PKCι, ERK1/2, AKT, YAP1 and mTOR. A nude mouse xenograft assay demonstrated that this drug combination strongly suppressed tumor volume compared with single drug treatment. CONCLUSIONS: Combination of IPA-3 or OTSSP167 and auranofin was highly synergistic in EGFR or KRAS mutant adenocarcinoma and squamous cell carcinoma cell lines and decreased tumor volume in mice models. It is of interest to further test the targeting of PKCι-PAK1 signaling pathways in EGFR mutant, KRAS mutant and squamous NSCLC patients.
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Adenocarcinoma/patología , Carcinoma de Pulmón de Células no Pequeñas/patología , Receptores ErbB/genética , Isoenzimas/metabolismo , Proteína Quinasa C/metabolismo , Proteínas Proto-Oncogénicas p21(ras)/genética , Transducción de Señal/efectos de los fármacos , Quinasas p21 Activadas/metabolismo , Células A549 , Adenocarcinoma/genética , Animales , Antineoplásicos/farmacología , Carcinogénesis/efectos de los fármacos , Carcinoma de Pulmón de Células no Pequeñas/genética , Supervivencia Celular/efectos de los fármacos , Interacciones Farmacológicas , Femenino , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/patología , Ratones , Terapia Molecular Dirigida , Mutación , Inhibidores de Proteínas Quinasas/farmacología , Ensayos Antitumor por Modelo de Xenoinjerto , Quinasas p21 Activadas/antagonistas & inhibidoresRESUMEN
BACKGROUND: Osimertinib improve therapy for non-small cell lung cancer (NSCLC). However, invariable acquired resistance appears. METHODS: MTT assay was used to analyze cell viability. Protein expression and activation was detected by Western blotting. In addition, the effects of heat shock protein 90 (Hsp90) inhibitors and osimertinib were studied in colony formation assays. RESULTS: Our laboratory generated osimertinib resistant cell lines from PC9 cell line and overexpression or activation of several proteins was detected. Hsp90 inhibitors, ganetespib and luminespib, inhibited cell viability and colony formation in H1975, PC9 and PC9-derived osimertinib-resistant cell lines and combination of these inhibitors with osimertinib achieved to enhance this cell viability and colony formation inhibition. Luminespib downregulated the expression of the several proteins involved in osimertinib-resistance and the combination of this compound plus osimertinib caused an important decrease of expression of several of these proteins, such as Stat3, Yap, Akt, EGFR and Met. Osimertinib activated the phosphorylation of several membrane receptors and downstream molecules that was partially inhibited by luminespib. In addition, a lung cancer patient with an EGFR eon 20 mutation had a partial radiographic response to ganetespib. CONCLUSIONS: Hsp90 inhibitors and osimertinib exhibits a good efficiency to inhibit cell viability, colony formation and inhibits expression and activation of proteins involved in osimertinib-resistance and may represent an effective strategy for NSCLC with intrinsic resistance to osimertinib inhibition.
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Non-small cell lung cancer (NSCLC) tumors harboring mutations in EGFR ultimately relapse to therapy with EGFR tyrosine kinase inhibitors (EGFR TKIs). Here, we show that resistant cells without the p.T790M or other acquired mutations are sensitive to the Aurora B (AURKB) inhibitors barasertib and S49076. Phospho-histone H3 (pH3), a major product of AURKB, is increased in most resistant cells and treatment with AURKB inhibitors reduces the levels of pH3, triggering G1/S arrest and polyploidy. Senescence is subsequently induced in cells with acquired mutations while, in their absence, polyploidy is followed by cell death. Finally, in NSCLC patients, pH3 levels are increased after progression on EGFR TKIs and high pH3 baseline correlates with shorter survival. Our results reveal that AURKB activation is associated with acquired resistance to EGFR TKIs, and that AURKB constitutes a potential target in NSCLC progressing to anti-EGFR therapy and not carrying resistance mutations.
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Antineoplásicos/farmacología , Aurora Quinasa B/metabolismo , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Neoplasias Pulmonares/tratamiento farmacológico , Inhibidores de Proteínas Quinasas/farmacología , Adulto , Anciano , Anciano de 80 o más Años , Animales , Antineoplásicos/uso terapéutico , Aurora Quinasa B/antagonistas & inhibidores , Aurora Quinasa B/genética , Carcinoma de Pulmón de Células no Pequeñas/genética , Carcinoma de Pulmón de Células no Pequeñas/mortalidad , Carcinoma de Pulmón de Células no Pequeñas/patología , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Progresión de la Enfermedad , Resistencia a Antineoplásicos/genética , Receptores ErbB/antagonistas & inhibidores , Receptores ErbB/genética , Femenino , Puntos de Control de la Fase G1 del Ciclo Celular/efectos de los fármacos , Histonas/metabolismo , Humanos , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/mortalidad , Neoplasias Pulmonares/patología , Masculino , Ratones , Persona de Mediana Edad , Organofosfatos/farmacología , Organofosfatos/uso terapéutico , Fosforilación/efectos de los fármacos , Poliploidía , Inhibidores de Proteínas Quinasas/uso terapéutico , Quinazolinas/farmacología , Quinazolinas/uso terapéutico , ARN Interferente Pequeño/metabolismo , Análisis de Supervivencia , Resultado del Tratamiento , Ensayos Antitumor por Modelo de XenoinjertoRESUMEN
INTRODUCTION: Epidermal growth factor receptor (EGFR) pathway deregulation promotes the acquisition of stemlike properties in non-small-cell lung cancer. EGFR inhibition through NOTCH enriches lung cancer stem cells (CSCs). Src through Yes-associated protein 1 (YAP1) activates NOTCH. Signal transduction and activator of transcription 3 (STAT3) activation occurs upon EGFR blockade and regulates the generation of CSCs. PATIENTS AND METHODS: Using the Aldefluor assay kit, we investigated the enrichment of aldehyde dehydrogenase (ALDH)-positive cells in EGFR-mutation-positive cells treated with gefitinib, afatinib, and osimertinib. Western blot analysis was performed to evaluate changes in CSC marker expression upon EGFR blockade. We performed gene expression analysis in a cohort of EGFR-mutation-positive non-small-cell lung cancer patients. We evaluated the association of gene expression with treatment outcomes. RESULTS: The cell subpopulation surviving EGFR inhibition had high ALDH activity and elevated CSC marker expression. Concurrent inhibition of EGFR, STAT3, and Src diminished the CSC subpopulation in an EGFR-mutation-positive cellular model. In a cohort of 64 EGFR-mutation-positive patients, 2 ALDH1 isoforms and the NOTCH target hairy and enhancer of split 1 (HES1), when highly expressed, were predictive of worse outcome to EGFR blockade. The gene expression of B-cell-specific Moloney murine leukemia virus integration site 1 (Bmi-1) that maintains the self-renewal of stem cells was also related to treatment outcome. CONCLUSION: Single EGFR inhibitors increase the population of CSCs. Combinatory therapy targeting STAT3 and Src may be of potential benefit. ALDH1, HES1, and Bmi-1 are essential biomarkers in the initial assessment of EGFR-mutation-positive patients.
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Familia de Aldehído Deshidrogenasa 1/metabolismo , Antineoplásicos/uso terapéutico , Biomarcadores de Tumor/metabolismo , Carcinoma de Pulmón de Células no Pequeñas/diagnóstico , Neoplasias Pulmonares/diagnóstico , Mutación/genética , Células Madre Neoplásicas/metabolismo , Factor de Transcripción HES-1/metabolismo , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Carcinoma de Pulmón de Células no Pequeñas/genética , Línea Celular Tumoral , Quimioterapia Combinada , Receptores ErbB/genética , Regulación Neoplásica de la Expresión Génica , Humanos , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/genética , Complejo Represivo Polycomb 1/metabolismo , Inhibidores de Proteínas Quinasas/farmacología , Factor de Transcripción STAT3/antagonistas & inhibidores , Familia-src Quinasas/antagonistas & inhibidoresRESUMEN
Immune checkpoint blockade has modified the treatment landscape for many types of tumors, including lung cancer. Still our knowledge on the biology of the interaction between tumor cells and the microenvironment is limited, preventing the optimal use of these new compounds and the maximum benefit that the patients can derive from them. We have actively worked on the role of STAT3, a transcriptional factor that causes innate resistance to targeted therapies in oncogene-addicted tumors. In this short review we take the opportunity to express our opinion and review existing knowledge on the immune role of STAT3 and the possible implications that this may have for the discovery of new biomarkers to predict response to immunotherapy, as well as new partners to combine with and increase the efficacy of immune checkpoint inhibitors.
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Non-small-cell lung cancer patients with activating epidermal growth factor receptor (EGFR) mutations typically benefit from EGFR tyrosine kinase inhibitor treatment. However, virtually all patients succumb to acquired EGFR tyrosine kinase inhibitor resistance that occurs via diverse mechanisms. The diversity and unpredictability of EGFR tyrosine kinase inhibitor resistance mechanisms presents a challenge for developing new treatments to overcome EGFR tyrosine kinase inhibitor resistance. Here, we show that Akt activation is a convergent feature of acquired EGFR tyrosine kinase inhibitor resistance, across a spectrum of diverse, established upstream resistance mechanisms. Combined treatment with an EGFR tyrosine kinase inhibitor and Akt inhibitor causes apoptosis and synergistic growth inhibition in multiple EGFR tyrosine kinase inhibitor-resistant non-small-cell lung cancer models. Moreover, phospho-Akt levels are increased in most clinical specimens obtained from EGFR-mutant non-small-cell lung cancer patients with acquired EGFR tyrosine kinase inhibitor resistance. Our findings provide a rationale for clinical trials testing Akt and EGFR inhibitor co-treatment in patients with elevated phospho-Akt levels to therapeutically combat the heterogeneity of EGFR tyrosine kinase inhibitor resistance mechanisms.EGFR-mutant non-small cell lung cancer are often resistant to EGFR tyrosine kinase inhibitor treatment. In this study, the authors show that resistant tumors display high Akt activation and that a combined treatment with AKT inhibitors causes synergistic tumour growth inhibition in vitro and in vivo.
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Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Receptores ErbB/antagonistas & inhibidores , Receptores ErbB/metabolismo , Neoplasias Pulmonares/metabolismo , Proteínas Proto-Oncogénicas c-akt/metabolismo , Animales , Apoptosis , Carcinoma de Pulmón de Células no Pequeñas/genética , Línea Celular Tumoral , Análisis Mutacional de ADN , Resistencia a Antineoplásicos , Activación Enzimática , Femenino , Humanos , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/genética , Ratones , Ratones SCID , Mutación , Trasplante de Neoplasias , Proteómica , Transducción de SeñalRESUMEN
Gefitinib, erlotinib or afatinib are the current treatment for non-small-cell lung cancer (NSCLC) harboring an activating mutation of the epidermal growth factor receptor (EGFR), but less than 5% of patients achieve a complete response and the median progression-free survival is no longer than 12 months. Early adaptive resistance can occur as soon as two hours after starting treatment by activating signal transducer and activation of transcription 3 (STAT3) signaling. We investigated the activation of STAT3 in a panel of gefitinib-sensitive EGFR mutant cell lines, and gefitinib-resistant PC9 cell lines developed in our laboratory. Afatinib has great activity in gefitinib-sensitive as well as in gefitinib-resistant EGFR mutant NSCLC cell lines. However, afatinib therapy causes phosphorylation of STAT3 tyrosine 705 (pSTAT3Tyr705) and elevation of STAT3 and RANTES mRNA levels. The combination of afatinib with TPCA-1 (a STAT3 inhibitor) ablated pSTAT3Tyr705 and down-regulated STAT3 and RANTES mRNA levels with significant growth inhibitory effect in both gefitinib-sensitive and gefitinib-resistant EGFR mutant NSCLC cell lines. Aldehyde dehydrogenase positive (ALDH+) cells were still observed with the combination at the time that Hairy and Enhancer of Split 1 (HES1) mRNA expression was elevated following therapy. Although the combination of afatinib with STAT3 inhibition cannot eliminate the potential problem of a remnant cancer stem cell population, it represents a substantial advantage and opportunity to further prolong progression free survival and probably could increase the response rate in comparison to the current standard of single therapy.
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Carcinoma de Pulmón de Células no Pequeñas/genética , Carcinoma de Pulmón de Células no Pequeñas/metabolismo , Receptores ErbB/genética , Neoplasias Pulmonares/genética , Neoplasias Pulmonares/metabolismo , Mutación , Factor de Transcripción STAT3/metabolismo , Transducción de Señal , Afatinib , Amidas/farmacología , Apoptosis/efectos de los fármacos , Carcinoma de Pulmón de Células no Pequeñas/patología , Línea Celular Tumoral , Supervivencia Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Resistencia a Antineoplásicos/genética , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Neoplasias Pulmonares/patología , Modelos Biológicos , Inhibidores de Proteínas Quinasas/farmacología , Quinazolinas/farmacología , Tiofenos/farmacologíaRESUMEN
BIM is a proapoptotic protein that initiates apoptosis triggered by EGFR tyrosine kinase inhibitors (TKI). mTOR negatively regulates apoptosis and may influence response to EGFR TKI. We examined mRNA expression of BIM and MTOR in 57 patients with EGFR-mutant NSCLC from the EURTAC trial. Risk of mortality and disease progression was lower in patients with high BIM compared with low/intermediate BIM mRNA levels. Analysis of MTOR further divided patients with high BIM expression into two groups, with those having both high BIM and MTOR experiencing shorter overall and progression-free survival to erlotinib. Validation of our results was performed in an independent cohort of 19 patients with EGFR-mutant NSCLC treated with EGFR TKIs. In EGFR-mutant lung adenocarcinoma cell lines with high BIM expression, concomitant high mTOR expression increased IC50 of gefitinib for cell proliferation. We next sought to analyse the signalling pattern in cell lines with strong activation of mTOR and its substrate P-S6. We showed that mTOR and phosphodiesterase 4D (PDE4D) strongly correlate in resistant EGFR-mutant cancer cell lines. These data suggest that the combination of EGFR TKI with mTOR or PDE4 inhibitors could be adequate therapy for EGFR-mutant NSCLC patients with high pretreatment levels of BIM and mTOR.
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Proteínas Reguladoras de la Apoptosis/genética , Carcinoma de Pulmón de Células no Pequeñas/genética , Receptores ErbB/genética , Clorhidrato de Erlotinib/uso terapéutico , Neoplasias Pulmonares/genética , Proteínas de la Membrana/genética , Mutación/genética , Proteínas Proto-Oncogénicas/genética , Serina-Treonina Quinasas TOR/genética , Anciano , Apoptosis/efectos de los fármacos , Apoptosis/genética , Proteínas Reguladoras de la Apoptosis/metabolismo , Proteína 11 Similar a Bcl2 , Carcinoma de Pulmón de Células no Pequeñas/tratamiento farmacológico , Carcinoma de Pulmón de Células no Pequeñas/patología , Estudios de Cohortes , Supervivencia sin Enfermedad , Clorhidrato de Erlotinib/farmacología , Femenino , Gefitinib , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Concentración 50 Inhibidora , Neoplasias Pulmonares/tratamiento farmacológico , Neoplasias Pulmonares/patología , Masculino , Proteínas de la Membrana/metabolismo , Persona de Mediana Edad , Proteínas Proto-Oncogénicas/metabolismo , Quinazolinas/farmacología , Quinazolinas/uso terapéutico , ARN Mensajero/genética , ARN Mensajero/metabolismo , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Serina-Treonina Quinasas TOR/metabolismo , Resultado del TratamientoRESUMEN
Alternative splicing is the mechanism by which different combinations of exons in the pre-mRNA give rise to distinct mature mRNAs. This process is mediated by splicing factors that bind the pre-mRNA and affect the recognition of its splicing signals. Saccharomyces species lack many of the regulatory factors present in metazoans. Accordingly, it is generally assumed that the amount of alternative splicing is limited. However, there is recent compelling evidence that yeast have functional alternative splicing, mainly in response to environmental conditions. We have previously shown that sequence and structure properties of the pre-mRNA could explain the selection of 3' splice sites (ss) in Saccharomyces cerevisiae. In this work, we extend our previous observations to build a computational classifier that explains most of the annotated 3'ss in the CDS and 5' UTR of this organism. Moreover, we show that the same rules can explain the selection of alternative 3'ss. Experimental validation of a number of predicted alternative 3'ss shows that their usage is low compared to annotated 3'ss. The majority of these alternative 3'ss introduce premature termination codons (PTCs), suggesting a role in expression regulation. Furthermore, a genome-wide analysis of the effect of temperature, followed by experimental validation, yields only a small number of changes, indicating that this type of regulation is not widespread. Our results are consistent with the presence of alternative 3'ss selection in yeast mediated by the pre-mRNA structure, which can be responsive to external cues, like temperature, and is possibly related to the control of gene expression.
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Empalme Alternativo , Regulación Fúngica de la Expresión Génica , Conformación de Ácido Nucleico , Precursores del ARN/química , Sitios de Empalme de ARN/genética , ARN de Hongos/química , Saccharomyces cerevisiae/genética , Codón de Terminación/genética , Biología Computacional , Precursores del ARN/genética , ARN de Hongos/genética , Selección GenéticaRESUMEN
The northern blot, or RNA gel blot, is a widely used method for the discovery, validation and expression analysis of small regulatory RNA such as small interfering RNA (siRNA), microRNA (miRNA) and piwi-interacting RNA (piRNA). Although it is straightforward and quantitative, the main disadvantage of a northern blot is that it detects such RNA less sensitively than most other approaches. We found that the standard dose of UV used in northern blots was not the most efficient at immobilizing small RNA of 20-40 nt on nylon membranes. However, increasing the dose of UV reduced the detection of miRNA by hybridization in northern blotting experiments. We discovered that using the soluble carbodiimide, EDC, to cross-link RNA to nylon membranes greatly improved the detection of small RNA by hybridization. Compared to standard UV cross-linking procedures, EDC cross-linking provided a 25-50-fold increase in the sensitivity of detection of siRNA from plants and miRNA or piRNA from mammalian cells. All types of hybridization probes tested benefited from the new cross-linking procedure. Cross-linking was dependent on a terminal phosphate and so, should be applicable to other related categories of small RNA.