Concomitant MEK and Cyclin Gene Alterations: Implications for Response to Targeted Therapeutics.

PURPOSE: Cyclin and MAPK/MEK-related gene alterations are implicated in cell-cycle progression and cancer growth. Yet, monotherapy to target the cyclin (CDK4/6) or the MEK pathway has often yielded disappointing results. Because coalterations in cyclin and MEK pathway genes frequently cooccur, we hypothesized that resistance to CDK4/6 or MEK inhibitor monotherapy might be mediated via activation of oncogenic codrivers, and that combination therapy might be useful. EXPERIMENTAL DESIGN: Herein, we describe 9 patients with advanced malignancies harboring concomitant CDKN2A and/or CDKN2B alterations (upregulate CDK4/6) along with KRAS or BRAF alterations (activate the MEK pathway) who were treated with palbociclib (CDK4/6 inhibitor) and trametinib (MEK inhibitor) combination-based regimens. RESULTS: Two patients (with pancreatic cancer) achieved a partial remission (PR) and, overall, 5 patients (56%) had clinical benefit (stable disease ≥ 6 months/PR) with progression-free survival of approximately 7, 9, 9, 11, and 17.5+ months. Interestingly, 1 of these patients whose cancer (gastrointestinal stromal tumor) had progressed on MEK targeting regimen, did well for about 1 year after palbociclib was added. CONCLUSIONS: These observations suggest that cotargeting cyclin and MEK signaling can be successful when tumors bear genomic coalterations that activate both of these pathways. Further prospective studies using this matching precision strategy to overcome resistance are warranted.See related commentary by Groisberg and Subbiah, p. 2672.

High prevalence of clonal hematopoiesis-type genomic abnormalities in cell-free DNA in invasive gliomas after treatment.

Plasma cell-free DNA (cfDNA) is emerging as an important diagnostic tool in cancer. However, cfDNA alterations may differ from those in tissue and sometimes may reflect processes unrelated to the cancer, including clonal hematopoiesis (CH). We examined plasma cfDNA, tested by next-generation sequencing (NGS), for characterized alterations (excluding variants of unknown significance) in 135 patients with invasive glioma. Overall, 21% (28/135) had ≥1 alteration; 17% (23/135) had CH-type cfDNA mutations. Temozolomide (a mutagenic alkylating agent) with concurrent radiation therapy prior to blood draw was significantly associated with an increase in CH-type mutations, even after age, race/ethnicity, and WHO-grade were considered as confounders (odds ratio [95% confidence interval, CI] 8.98 [1.13-71.46]; P = .04; multivariable analysis). Further, of 18 patients with invasive glioma who had both cfDNA and tissue DNA NGS and had ≥1 cfDNA alteration, 16 (89%) had ≥1 cfDNA alteration not found in their tissue DNA, including CH-type alterations in genes such as TP53 (most common), ATM, GNAS, and JAK2. Altogether, 87% of cfDNA alterations (20/23) observed in the 18 patients were implicated in CH. Finally, examining all 135 patients, CH-type cfDNA mutations were an independent prognostic factor for shorter survival (hazard ratio [95% CI] 3.28 [1.28-8.40]; P = .01). These findings emphasize that not all characterized cfDNA alterations detected in patients with solid tumors are cancer-related. Importantly, in patients with invasive gliomas who have had prior temozolomide and radiation, CH-related alterations in cfDNA are frequent and correlate with poor outcomes.

Human Nontumorigenic Microglia Synthesize Strongly Fluorescent Au/Fe Nanoclusters, Retaining Bioavailability.

The ability for cells to self-synthesize metal-core nanoclusters (mcNCs) offers increased imaging and identification opportunities. To date, much work has been done illustrating the ability for human tumorigenic cell lines to synthesize mcNCs; however, this has not been illustrated for nontumorigenic cell lines. Here, we present the ability for human nontumorigenic microglial cells, which are the major immune cells in the central nervous system, to self-synthesize gold (Au) and iron (Fe) core nanoclusters, following exposures to metallic salts. We also show the ability for cells to internalize presynthesized Au and Fe mcNCs. Cellular fluorescence increased in most exposures and in a dose dependent manner in the case of Au salt. Scanning transmission electron microscopic imaging confirmed the presence of the metal within cells, while transmission electron microscopy images confirmed nanocluster structures and self-synthesis. Interestingly, self-synthesized nanoclusters were of similar size and internal structure as presynthesized mcNCs. Toxicity assessment of both salts and presynthesized NCs illustrated a lack of toxicity from Au salt and presynthesized NCs. However, Fe salt was generally more toxic and stressful to cells at similar concentrations.

ARID1A alterations function as a biomarker for longer progression-free survival after anti-PD-1/PD-L1 immunotherapy.

BACKGROUND: Several cancer types harbor alterations in the gene encoding AT-Rich Interactive Domain-containing protein 1A (ARID1A), but there are no approved therapies to address these alterations. Recent studies have shown that ARID1A deficiency compromises mismatch repair proteins. Herein, we analyzed 3403 patients who had tumor tissue next-generation sequencing. FINDINGS: Among nine cancer subtypes with >5% prevalence of ARID1A alterations, microsatellite instability-high as well as high tumor mutational burden was significantly more frequent in ARID1A-altered versus ARID1A wild-type tumors (20% vs 0.9%, p<0.001; and 26% vs 8.4%, p<0.001, respectively). Median progression-free survival (PFS) after checkpoint blockade immunotherapy was significantly longer in the patients with ARID1A-altered tumors (n=46) than in those with ARID1A wild-type tumors (n=329) (11 months vs 4 months, p=0.006). Also, multivariate analysis showed that ARID1A alterations predicted longer PFS after checkpoint blockade (HR (95% CI), 0.61 (0.39 to 0.94), p=0.02) and this result was independent of microsatellite instability or mutational burden; median overall survival time was also longer in ARID1A-altered versus wild-type tumors (31 months vs 20 months), but did not reach statistical significance (p=0.13). CONCLUSIONS: Our findings suggest that ARID1A alterations merit further exploration as a novel biomarker correlating with better outcomes after checkpoint blockade immunotherapy.

Burkholderia pseudomallei, the causative agent of melioidosis, is rare but ecologically established and widely dispersed in the environment in Puerto Rico.

BACKGROUND: Burkholderia pseudomallei is a soil-dwelling bacterium and the causative agent of melioidosis. The global burden and distribution of melioidosis is poorly understood, including in the Caribbean. B. pseudomallei was previously isolated from humans and soil in eastern Puerto Rico but the abundance and distribution of B. pseudomallei in Puerto Rico as a whole has not been thoroughly investigated. METHODOLOGY/PRINCIPAL FINDINGS: We collected 600 environmental samples (500 soil and 100 water) from 60 sites around Puerto Rico. We identified B. pseudomallei by isolating it via culturing and/or using PCR to detect its DNA within complex DNA extracts. Only three adjacent soil samples from one site were positive for B. pseudomallei with PCR; we obtained 55 isolates from two of these samples. The 55 B. pseudomallei isolates exhibited fine-scale variation in the core genome and contained four novel genomic islands. Phylogenetic analyses grouped Puerto Rico B. pseudomallei isolates into a monophyletic clade containing other Caribbean isolates, which was nested inside a larger clade containing all isolates from Central/South America. Other Burkholderia species were commonly observed in Puerto Rico; we cultured 129 isolates from multiple soil and water samples collected at numerous sites around Puerto Rico, including representatives of B. anthina, B. cenocepacia, B. cepacia, B. contaminans, B. glumae, B. seminalis, B. stagnalis, B. ubonensis, and several unidentified novel Burkholderia spp. CONCLUSIONS/SIGNIFICANCE: B. pseudomallei was only detected in three soil samples collected at one site in north central Puerto Rico with only two of those samples yielding isolates. All previous human and environmental B. pseudomallei isolates were obtained from eastern Puerto Rico. These findings suggest B. pseudomallei is ecologically established and widely dispersed in the environment in Puerto Rico but rare. Phylogeographic patterns suggest the source of B. pseudomallei populations in Puerto Rico and elsewhere in the Caribbean may have been Central or South America.

A Rab5 endosomal pathway mediates Parkin-dependent mitochondrial clearance.

Damaged mitochondria pose a lethal threat to cells that necessitates their prompt removal. The currently recognized mechanism for disposal of mitochondria is autophagy, where damaged organelles are marked for disposal via ubiquitylation by Parkin. Here we report a novel pathway for mitochondrial elimination, in which these organelles undergo Parkin-dependent sequestration into Rab5-positive early endosomes via the ESCRT machinery. Following maturation, these endosomes deliver mitochondria to lysosomes for degradation. Although this endosomal pathway is activated by stressors that also activate mitochondrial autophagy, endosomal-mediated mitochondrial clearance is initiated before autophagy. The autophagy protein Beclin1 regulates activation of Rab5 and endosomal-mediated degradation of mitochondria, suggesting cross-talk between these two pathways. Abrogation of Rab5 function and the endosomal pathway results in the accumulation of stressed mitochondria and increases susceptibility to cell death in embryonic fibroblasts and cardiac myocytes. These data reveal a new mechanism for mitochondrial quality control mediated by Rab5 and early endosomes.

Autophagy and mitophagy in the myocardium: therapeutic potential and concerns.

The autophagic-lysosomal degradation pathway is critical for cardiac homeostasis, and defects in this pathway are associated with development of cardiomyopathy. Autophagy is responsible for the normal turnover of organelles and long-lived proteins. Autophagy is also rapidly up-regulated in response to stress, where it rapidly clears dysfunctional organelles and cytotoxic protein aggregates in the cell. Autophagy is also important in clearing dysfunctional mitochondria before they can cause harm to the cell. This quality control mechanism is particularly important in cardiac myocytes, which contain a very high volume of mitochondria. The degradation of proteins and organelles also generates free fatty acids and amino acids, which help maintain energy levels in myocytes during stress conditions. Increases in autophagy have been observed in various cardiovascular diseases, but a major question that remains to be answered is whether enhanced autophagy is an adaptive or maladaptive response to stress. This review discusses the regulation and role of autophagy in the myocardium under baseline conditions and in various aetiologies of heart disease. It also discusses whether this pathway represents a new therapeutic target to treat or prevent cardiovascular disease and the concerns associated with modulating autophagy.

Parkin protein deficiency exacerbates cardiac injury and reduces survival following myocardial infarction.

It is known that loss-of-function mutations in the gene encoding Parkin lead to development of Parkinson disease. Recently, Parkin was found to play an important role in the removal of dysfunctional mitochondria via autophagy in neurons. Although Parkin is expressed in the heart, its functional role in this tissue is largely unexplored. In this study, we have investigated the role of Parkin in the myocardium under normal physiological conditions and in response to myocardial infarction. We found that Parkin-deficient (Parkin(-/-)) mice had normal cardiac function for up to 12 months of age as determined by echocardiographic analysis. Although ultrastructural analysis revealed that Parkin-deficient hearts had disorganized mitochondrial networks and significantly smaller mitochondria, mitochondrial function was unaffected. However, Parkin(-/-) mice were much more sensitive to myocardial infarction when compared with wild type mice. Parkin(-/-) mice had reduced survival and developed larger infarcts when compared with wild type mice after the infarction. Interestingly, Parkin protein levels and mitochondrial autophagy (mitophagy) were rapidly increased in the border zone of the infarct in wild type mice. In contrast, Parkin(-/-) myocytes had reduced mitophagy and accumulated swollen, dysfunctional mitochondria after the infarction. Overexpression of Parkin in isolated cardiac myocytes also protected against hypoxia-mediated cell death, whereas nonfunctional Parkinson disease-associated mutants ParkinR42P and ParkinG430D had no effect. Our results suggest that Parkin plays a critical role in adapting to stress in the myocardium by promoting removal of damaged mitochondria.

Speech recognition and subjective perceptions of neck-loop FM receivers with cochlear implants.

PURPOSE: The goal of this investigation was to determine the potential benefit of using electromagnetically coupled frequency modulation (FM) neck-loop receivers to address common communication difficulties of adults and adolescents with cochlear implants (CIs). METHOD: Fourteen participants with CIs used the neck-loop FM receiver for a trial period and participated in pre- and post trial sessions consisting of speech-recognition-in-noise measures with and without the FM system and a subjective rating scale. Most participants also recorded their experiences during the FM-system trial period in a journal. RESULTS: The results suggested significantly improved speech recognition in noise with the neck-loop FM system before and after the trial period, with no changes in performance between test sessions. On average, the rating scale and journals revealed improvements with the FM system, relative to the CI alone, in noisy environments or situations at a distance from the primary talker or sound source. CONCLUSION: The results of the study suggest that neck-loop FM receivers significantly improved speech recognition in noise and everyday listening challenges of people using the CIs in 2 separate test sessions. Additional research is warranted for other types of neck-loop receivers and CI sound processors.