The Neoarchaean surficial sulphur cycle: An alternative hypothesis based on analogies with 20th-century atmospheric lead

We revisit the S-isotope systematics of sedimentary pyrite in a shaly limestone from the ca. 2.52 Ga Gamohaan Formation, Upper Campbellrand Subgroup, Transvaal, South Africa. The analysed rock is interpreted to have been deposited in a water depth of ca. 50-100 m, in a restricted sub-basin on a drowning platform. A previous study discovered that the pyrites define a nonzero intercept δ³⁴ S_V-CDT -Δ³³ S data array. The present study carried out further quadruple S-isotope analyses of pyrite, confirming and expanding the linear δ³⁴ S_V-CDT -Δ³³ S array with an δ³⁴ S zero intercept at ∆³³ S ca. +5. This was previously interpreted to indicate mixing of unrelated S-sources in the sediment environment, involving a combination of recycled sulphur from sulphides that had originally formed by sulphate-reducing bacteria, along with elemental sulphur. Here, we advance an alternative explanation based on the recognition that the Archaean seawater sulphate concentration was likely very low, implying that the Archaean ocean could have been poorly mixed with respect to sulphur. Thus, modern oceanic sulphur systematics provide limited insight into the Archaean sulphur cycle. Instead, we propose that the 20th-century atmospheric lead event may be a useful analogue. Similar to industrial lead, the main oceanic input of Archaean sulphur was through atmospheric raindown, with individual giant point sources capable of temporally dominating atmospheric input. Local atmospheric S-isotope signals, of no global significance, could thus have been transmitted into the localised sediment record. Thus, the nonzero intercept δ³⁴ S_V-CDT -Δ³³ S data array may alternatively represent a very localised S-isotope signature in the Neoarchaean surface environment. Fallout from local volcanic eruptions could imprint recycled MIF-S signals into pyrite of restricted depositional environments, thereby avoiding attenuation of the signal in the subdued, averaged global open ocean sulphur pool. Thus, the superposition of extreme local S-isotope signals offers an alternative explanation for the large Neoarchaean MIF-S excursions and asymmetry of the Δ³³ S rock record.

Gaps and barriers in health-care provision for co-morbid diabetes and chronic kidney disease: a cross-sectional study

BACKGROUND

Patients with diabetes and chronic kidney disease (CKD) are a complex subset of the growing number of patients with diabetes, due to multi-morbidity. Gaps between recommended and received care for diabetes and chronic kidney disease (CKD) are evident despite promulgation of guidelines. Here, we document gaps in tertiary health-care, and the commonest patient-reported barriers to health-care, before exploring the association between these gaps and barriers.

METHODS

This cross-sectional study recruited patients with diabetes and CKD (eGFR < 60 mL/min/1.73 m2) across 4 large hospitals. For each patient, questionnaires were completed examining clinical data, recommended care, and patient-reported barriers limiting health-care. Descriptive statistics, subgroup analyses by CKD stage and hospital, and analyses examining the relationship between health-care gaps and barriers were performed.

RESULTS

308 patients, of mean age 66.9 (SD 11.0) years, and mostly male (69.5%) and having type 2 diabetes (88.0%), participated. 49.1% had stage 3, 24.7% stage 4 and 26.3% stage 5 CKD. Gaps between recommended versus received care were evident: 31.9% of patients had an HbA1c ≥ 8%, and 39.3% had a measured blood pressure ≥ 140/90 mmHg. The commonest barriers were poor continuity of care (49.3%), inadequate understanding/education about CKD (43.5%), and feeling unwell (42.6%). However, barriers associated with a failure to receive items of recommended care were inadequate support from family and friends, conflicting advice from and poor communication amongst specialists, the effect of co-morbidities on self-management and feeling unmotivated (all p < 0.05).

CONCLUSIONS

Barriers to health-care varied across CKD stages and hospitals. Barriers associated with a deviation from recommended care were different for different items of care, suggesting that specific interventions targeting each item of care are required.

Sudden cardiac arrest due to a single sodium channel mutation producing a mixed phenotype of Brugada and Long QT3 syndromes

Inherited arrhythmia syndromes are a known, albeit rare, cause of sudden cardiac arrest which may present with characteristic electrocardiogram changes in patients with structurally normal heart. There are a variety of distinct arrhythmogenic syndromes that arise from mutations in voltage gated sodium channels, resulting in either gain or loss of function. We describe a patient with a primary inherited arrhythmia syndrome which presented as sudden cardiac arrest. Further workup revealed that her arrest was due to a combination of Brugada syndrome and Long QT3 syndrome secondary to a deleterious mutation of voltage-gated, sodium channel, type V alpha subunit (SCN5A Thr1709Met).

Cross-validation of Peak Oxygen Consumption Prediction Models From OMNI Perceived Exertion

This study cross-validated statistical models for prediction of peak oxygen consumption using ratings of perceived exertion from the Adult OMNI Cycle Scale of Perceived Exertion. 74 participants (men: n=36; women: n=38) completed a graded cycle exercise test. Ratings of perceived exertion for the overall body, legs, and chest/breathing were recorded each test stage and entered into previously developed 3-stage peak oxygen consumption prediction models. There were no significant differences (p>0.05) between measured and predicted peak oxygen consumption from ratings of perceived exertion for the overall body, legs, and chest/breathing within men (mean±standard deviation: 3.16±0.52 vs. 2.92±0.33 vs. 2.90±0.29 vs. 2.90±0.26 L·min(-1)) and women (2.17±0.29 vs. 2.02±0.22 vs. 2.03±0.19 vs. 2.01±0.19 L·min(-1)) participants. Previously developed statistical models for prediction of peak oxygen consumption based on subpeak OMNI ratings of perceived exertion responses were similar to measured peak oxygen consumption in a separate group of participants. These findings provide practical implications for the use of the original statistical models in standard health-fitness settings.

Abstract P6-13-08: Palbociclib and paclitaxel on an alternating schedule for advanced breast cancer: Results of a phase Ib trial

Background: Palbociclib (P) is an oral CDK 4/6 inhibitor (CDKi) that was recently FDA approved in combination with endocrine therapy for metastatic breast cancer. We have performed a Phase I trial of P in combination with paclitaxel (T) based on preclinical studies suggesting that P synergizes with T when given on an alternating schedule, enabling cell cycle synchronization in tumor cells. We now present the dose expansion cohort.

Methods: Patients (Pts) enrolled on the trial had Rb-expressing tumors of any estrogen/progesterone/HER2 receptor type, adequate organ function, and ≤3 prior chemotherapy regimens for metastatic breast cancer (mBC). Prior adjuvant or metastatic taxane was allowed. Dose escalation led to expansion at P100mg or 75mg, starting with 3 days of P (run-in) and reduction of P dosing from 5-day to 3-day intervals (days 2-4, 9-11, 16-18 of each 28 day cycle). T at 80mg/m2 was given weekly for 3 cycles; thereafter, T was administered days 1, 8 and 15 of 28 day cycle. Weekly toxicity assessments were performed; RECIST 1.0 response was assessed every 2 cycles as partial response (PR), stable disease (SD) or progressive disease (PD). Pts had the option to discontinue T and continue on P alone (3 on/1 off schedule) if they attained SD after cycle 6.

Results: 27 pts enrolled on study (15- dose escalation, 12- dose expansion). Results are shown in the Table. 21 pts had received prior taxane; pts had received a median of 2 chemotherapy regimens for mBC. DLTs were grade 3 AST/ALT (n=1, at 125 mg) and febrile neutropenia (FN) (n=1, at 100 mg). Uncomplicated grade 3/4 NTP was common and frequently led to dose reduction or dose interruption during the first cycle of therapy. Frequency of NTP did not change with reducing the days of P. Among 24 evaluable patients, 14 (58%), had PR or SD ≥ 6 months across all dose levels. Of 14 pts who responded, 10 (71%) had received prior taxane. 20 pts are off study; 19 for PD, and 2 for toxicity (NTP in cycle 17 and FN in cycle 1); 7 pts remain on study. Prolonged tumor responses were seen.

Conclusions: P and T can be safely combined on an alternating dosing schedule; the optimal combination dose is 75 mg of P and 80mg/m2 of weekly T. The high response rate warrants a randomized trial to determine the incremental benefit over T alone. Additional mechanistic studies are in progress to understand the in vivo effects of the alternating dosing schedule on cell cycle activity and tumor proliferation.

Starting Dose Level P (mg)Number (Total 27)DLTGrade 3/4 NTP (n)Final Dose P mg (n)Dose Interruption (n)Best Response (n)5030050 (1) 50 (1) 50 (1)No (2) Yes (1)PR (1) SD (1) PD (1)7530275 (1) 50 (1) 25 (1)No (1) Yes (2)PR (2) SD (1)100605100 (2) 75 (3) 25 (1)No (1) Yes (5)PR (2) SD (1) PD (3)12531- LFT375 (1) 50 (2)No (0) Yes (3)PR (1) SD (2)75 (Run-In)60175 (5) 50 (1)No (4) Yes (2)PR (1) SD (2) PD (1) N/A (2)*100 (Run-In)61- FN5100 (1) 75 (4) 25(1)No (1) Yes (5)PR (4) SD (1) N/A (1)^*2 pts not yet evaluable. ^1 pt went off study due to FN after cycle 1.

Citation Format: Clark AS, O'Dwyer P, Troxel A, Lal P, Feldman M, Gallagher M, Driscoll A, Colameco C, Lewis D, Rosen M, Matro J, Bradbury A, Domchek S, Fox K, DeMichele A. Palbociclib and paclitaxel on an alternating schedule for advanced breast cancer: Results of a phase Ib trial. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-13-08.

Abstract P4-13-04: Upregulation of cell cycle pathway genes without loss of RB1 contributes to acquired resistance to single-agent treatment with palbociclib in breast cancer

Background: The oral cdk4/6 inhibitor, Palbociclib (Palbo), has been shown to prolong progression-free survival when combined with anti-estrogen therapy and have single-agent activity in metastatic breast cancer (MBC). Progressive disease (PD) on therapy does occur, however, and little is known about resistance mechanisms. Preclinical data have suggested that cell cycle gene expression changes are a potential mechanism of resistance. We performed comprehensive genomic analyses on serial tumor samples from an exceptional responder to single-agent Palbo to determine whether such changes occur in vivo.

Methods: Serial biopsies were obtained from a 67 year old patient with MBC treated on a phase II trial of single-agent Palbo at the University of Pennsylvania. Tissue was obtained from the primary lesion (1999, Stage 3, ER-/PR+/Her2+) and first recurrence (2005, contralateral breast, bone, lung; ER+/PR-/Her2+, treated with Herceptin/letrozole). At PD (2010), pt received single-agent P, 50 mg daily for 21 days each 28-day cycle, with PR for 33 months. A sample from metastatic skin lesion at PD on P (2013) was obtained. Next generation targeted sequencing was performed at Foundation Medicine using the Heme Panel. RNA was profiled using a 784-gene custom Nanostring array including cell cycle genes and ER pathway genes. Determination of pathway enrichment was performed using GSEA and the statistical significance of network neighborhood over-representation was calculated using cumulative hypergeometric distribution.

Results: There was no genetic evidence suggesting loss of RB1, or alterations in p16, cyclin D1, cdk4, PIK3CA or ESR1, and the genomic profile did not change between the primary and recurrent tissue samples. As expected, amplification of ERRB2 was present in all samples. In contrast, expression of cell cycle-regulated genes (PLK1, TOP2A, CDK1, BUB1, CDC20, CCNA2, CCNE2, CCNB1 BIRC5) increased more than two-fold at PD on Palbo compared to pre-Palbo, along with evidence of activation of the FOXM1 network.

Conclusion: Gene expression changes associated with cell cycle activation and FOXM1 activation may lead to acquired resistance to Palbociclib, despite wild-type RB1. These data demonstrate the importance of pre-/post-treatment biopsies and the feasibility of high-level genomic assessment in archival tissues to elucidate resistance mechanisms of novel therapies.

Citation Format: DeMichele A, Shih NNC, Koehler M, Huang Bartlett C, Jiang Y, Harwick J, Huang D, Zheng X, Clark AS, Colameco C, Feldman MD, Gallagher M, Goodman N, O'Dwyer P, Rejto P. Upregulation of cell cycle pathway genes without loss of RB1 contributes to acquired resistance to single-agent treatment with palbociclib in breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-13-04.