BackgroundCurrent diagnostic and prognostic blood-based biomarkers for neuroendocrine tumors are limited. MiRNAs have tumor-specific expression patterns, are relatively stable, and can be measured in patient blood specimens. We performed a multi-stage study to identify and validate characteristic circulating miRNAs in patients with metastatic small intestine neuroendocrine tumors, and to assess associations between miRNA levels and survival.MethodsUsing a 742-miRNA panel, we identified candidate miRNAs similarly expressed in 19 small intestine neuroendocrine tumors and matched plasma samples. We refined our panel in an independent cohort of plasma samples from 40 patients with metastatic small intestine NET and 40 controls, and then validated this panel in a second, large cohort of 120 patients with metastatic small intestine NET and 120 independent controls.ResultsmiRNA profiling of 19 matched small intestine neuroendocrine tumors and matched plasma samples revealed 31 candidate miRNAs similarly expressed in both tissue and plasma. We evaluated expression of these 31 candidate miRNAs in 40 independent cases and 40 normal controls, and identified 4 miRNAs (miR-21-5p, miR-22-3p, miR-29b-3p, and miR-150-5p) that were differently expressed in cases and controls (p<0.05). We validated these 4 miRNAs in a separate, larger panel of 120 cases and 120 controls. We confirmed that high circulating levels of miR-22-3p (p<0.0001), high levels of miR 21-5p, and low levels of miR-150-5p (p=0.027) were associated with the presence of metastatic small intestine NET. While levels of 29b-3p were lower in cases than in controls in both the initial cohort and the validation cohort, the difference in the validation cohort did not reach statistical significance. We further found that high levels of circulating miR-21-5p, high levels of circulating miR-22-3p and low levels of circulating miR-150-5p were each independently associated with shorter overall survival. A combined analysis using all three markers was highly prognostic for survival (HR 0.47, 95% CI 0.27-0.82).ConclusionsOur study suggests that elevated circulating levels of miR-21-5p and miR-22-3p and low levels of miR-150-5p are characteristic in patients with metastatic small intestine neuroendocrine tumors, and further suggests that levels of these miRNAs are associated with overall survival. These observations provide the basis for further validation studies, as well as studies to assess the biological function of these miRNAs in small intestine neuroendocrine tumors.
TBR-760 (formerly BIM-23A760) is a chimeric dopamine (DA)-somatostatin (SST) compound with potent agonist activity at both DA type 2 (D2R) and SST type 2 (SSTR2) receptors. Studies have shown that chimeric DA-SST compounds are more efficacious than individual DA and/or SST analogs, either alone or combined, in inhibiting secretion from primary cultures of human somatotroph and lactotroph tumor cells. Non-functioning pituitary adenomas (NFPAs) express both D2R and SSTR2 and, consequently, may respond to TBR-760. We utilized a mouse model with the pro-opiomelanocortin (POMC) gene knocked-out that spontaneously develops aggressive NFPAs. Genomic microarray and DA and SST receptor mRNA expression analysis indicate that POMC KO mouse tumors and human NFPAs have similar expression profiles, despite arising from different cell lineages, establishing POMC KO mice as a model for study of NFPAs. Treatment with TBR-760 for 8 weeks resulted in nearly complete inhibition of established tumor growth, whereas tumors from vehicle-treated mice increased in size by 890 ± 0.7%. Comparing TBR-760 with its individual DA and SST components, TBR-760 arrested tumor growth. Treatment with equimolar or 10x-higher doses of the individual SST or DA agonists, either alone or in combination, had no significant effect. One exception was the lower dose of DA agonist that induced modest suppression of tumor growth. Only the chimeric compound TBR-760 arrested tumor growth in this mouse model of NFPA. Further, significant tumor shrinkage was observed in 20% of the mice treated with TBR-760. These results support the development of TBR-760 as a therapy for patients with NFPA.
TBR-760 is a chimeric dopamine (DA)-somatostatin (SST) compound with potent agonist activity at both DA type 2 (D2R; EC50 0.064nM) and SST type 2 (SSTR2; EC50 1.2nM) receptors. Prior studies have demonstrated that the chimeric DA-SST compounds are more potent and effective than either individual or combinations of individual DA and/or SST analogs in inhibiting secretion from pituitary adenomas. Non-functioning pituitary adenomas (NFPA) express high levels of D2R as well as lower levels of SSTRs, including the type 2 receptor (1), and thus have an appropriate receptor profile to respond to TBR-760. The present study examines the ability of TBR-760 to inhibit tumor growth in a mouse model of aggressive NFPA. Heterozygous and null mutant mice lacking one or both copies, respectively, of the pro-opiomelanocortin (POMC) gene (POMC-KO mice)(2) spontaneously develop aggressive, non-secreting pituitary adenomas (3). The POMC-KO mouse tumors have been shown to express D2R and SSTR2 at a similar level as human NFPAs (4). In addition, merging of microarray data (Affymetrix, U133 plus_2.0 and Mouse Genome 430 2.0 arrays), reveals 154 common gene signatures between human NFPAs and the POMC-KO mouse tumors. In an initial study, heterozygous POMC-KO mice with an established pituitary tumor of approx. 10mm3 (mean volume 8.9±0.3), as determined by MRI, were treated with a range of TBR-760 doses (0.125 to 12.5mg/kg, sc, QD) for 60 days. During that time, tumors in vehicle-treated mice increased in size by 890±0.7%, whereas all doses of TBR-760 tested resulted in a nearly complete inhibition of tumor growth from treatment initiation. We then compared the effect of the TBR-760 chimera with that of its individual SST agonist (SSTA) and DA agonist (DAA) components on tumor growth in the POMC-KO mice. As in the earlier study, TBR-760 treatment (1mg/kg, sc, QD), initiated when the mice had an established tumor of approx. 10mm3, completely arrested tumor growth during the 8 weeks of treatment (final mean tumor volume of 8.5±1.3mm3 vs. 54.61±10.6mm3 in vehicle-treated mice). Treatment with equimolar or 10x-higher doses of the individual SSTA or DAA, either alone or in combination, had no significant effect on tumor growth, except in the lower dose DAA group where a modest suppression of tumor growth was observed. These data demonstrate that only the dual DA-SST chimeric compound, TBR-760, completely arrested tumor growth in the POMC-KO mouse model of NFPA. Further, despite the highly aggressive nature of the POMC-KO tumors, significant tumor shrinkage was observed in 20% of the mice treated with TBR-760. These results support the development of TBR-760 as a medical therapy to prevent or arrest the growth of NFPAs and, potentially, to induce NFPA shrinkage. References: (1) Florio et al., 2008 Endocr Relat Cancer; 15: 583-596. (2) Yaswen et al., 1999 Nat Med; 9:1066-70 (3) Karpac J et al., 2006 Cell Mol Biol; 52: 47-52.
Introduction: Detection of ctDNA in plasma samples permits temporal assessment of tumor mutation status during treatment. Poziotinib is an oral pan-HER TKI that has been demonstrated to be efficacious in NSCLC patients harboring HER2 exon 20 insertion mutations. We assessed serial plasma samples for changes in tumor genotype in both treatment naive and second line patients to evaluate correlation with clinical response. Methods: For NSCLC patients, HER2 exon 20 insertion mutations identified by tumor tissue based NGS were required for entry into the ZENITH20 study. Plasma samples were collected prior to treatment and at C3D1 (8 weeks post treatment 16mg poziotinib QD). The Guardant360® 74-gene liquid biopsy assay, which assessed changes in ctDNA and, subsequently, mean variant allele fraction (mVAF), was utilized for analysis of samples. The Guardant360 Response™ Molecular Response (MR) algorithm was calculated as a ratio of mVAF of oncogenic alterations at baseline compared to poziotinib treatment at C3D1. Results: 23 patients with tumor tissue confirmed NSCLC harboring HER2 exon 20 insertion mutations were studied. 22 of 23 (96%) had baseline plasma samples with detectable ctDNA. 21 of 22 samples had detectable HER2 exon 20 insertion mutations, resulting in a concordance of 95% versus tissue based NGS. The most prevalent HER2 exon 20 insertion alteration was the A775_G776ins YVMA variant, found in 50% of the baseline blood and tumor samples using both methods (100% concordance). 16 of 17 patients had both baseline and C3D1 samples, permitting assessment of temporal response. 15 of the 16 (94%) patients demonstrated a decrease in mVAF at C3D1 compared to the mVAF at baseline. 12 of 15 patients demonstrated an >50% reduction in mVAF at C3D1, with 7 of the 12 patients showing >95% reduction in mVAF at C3D1 with clinical outcomes of 5 PRs, 1 non-CR/non-PD and 1 SD. Interestingly, 3 of these patients showed complete clearance of ctDNA target HER2 exon 20 insertions at the C3D1 timepoint. Conclusions: Baseline plasma ctDNA genotyping correlated with tumor tissue based NGS in an NSCLC patient population with HER2 mutations. Poziotinib treatment resulted in mVAF reduction, which correlated with clinical response per RECIST1.1. Assessment of longitudinal changes in ctDNA during drug therapy may potentially be used to predict patient response and possibly tumor resistance. Further evaluation in larger cohorts and longer duration of treatment is required to help elucidate the impact of these findings. Citation Format: Arunthi Thiagalingam, Sribalaji Lakshmikanthan, Allysia J. Mak, Scott A. Shell, Sharon Leu, Rocky Washington, Lyndah Dreiling, Gajanan Bhat, Francois Lebel, John A. Barrett. Predictive ability of circulating tumor DNA by Guardant360 in poziotinib-treated patients with NSCLC harboring HER2 exon 20 insertion mutations [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3400.
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