Real world outcomes of minimally invasive epicardial surgical left atrial appendage exclusion in atrial fibrillation patients with high risk of stroke and bleeding

Funding Acknowledgements

Type of funding sources: Private company. Main funding source(s): AtriCure, Inc

Introduction

The left atrial appendage (LAA) is the site of thrombus formation in patients with atrial fibrillation (AF) and first line therapy for reducing the risk of stroke is oral anticoagulation (OACs). A subset of patients with AF carry a very high risk of stroke and bleeding and are ineligible for OAC and percutaneous LAA occlusion; these patients may be suitable for minimally invasive thoracoscopic epicardial surgical LAA exclusion (LAAE) which can be used with a wide variety of LAA morphologies with a ~98% rate of complete exclusion. While use of LAAE is well studied as a concomitant procedure, there are relatively few data on its use as a stand-alone procedure.

Purpose

To compare real-world outcomes of LAAE versus no-LAAE in AF patients at high risk of stroke and bleeding who are not on OACs.

Methods

We performed an analysis of Medicare beneficiaries with AF who were not on OACs and received LAAE (ICD10-PCS code 02L74CK, Oct 2015 – Dec 31, 2017) in the absence of a concomitant surgical or catheter AF ablation procedure. Patients were propensity-matched (1:4) to otherwise similar patients who did not receive LAAE (control), using age, gender, race, region, AF type, CHA2DS2-VASc, HAS-BLED, and co-morbidities. The primary endpoint was hospital readmission for a thromboembolic event (ischemic stroke, systemic embolism, or transient ischemic attack). Kaplan Meier event rates were calculated and 95% CI were generated via bootstrapping.

Results

A total of 243 patients who underwent LAAE and 1.7M control patients met study criteria. In the matched cohort, the mean age was 75 years, 61% were men, 77% had non-paroxysmal AF, and the mean CHADS2-VASC and HAS-BLED scores were 5.5 and 4.2, respectively. The 1-year rate of thromboembolism in the LAAE and control arms were 7.3% (95% CI 4.3% -10.9%) and 13.6 (95% CI 11.0% -16.4%) (Figure), respectively, with an absolute and relative risk reduction of 6.2% (95% CI 2.0-10.3, p-value=0.001, NNT 17) and 0.54 (95% CI 0.29-0.68, p=0.001).

Conclusion

Among high-risk AF patients who were not on OAC, LAAE was associated with a clinically meaningful and significantly lower risk of TE. Additional studies are needed to confirm these finding.

Anticancer activity of 2'-hydroxyflavanone towards lung cancer

In previous studies, we found that 2'-hydroxyflavonone (2HF), a citrus flavonoid, inhibits the growth of renal cell carcinoma in a VHL-dependent manner. This was associated with the inhibition of glutathione S-transferases (GSTs), the first step enzyme of the mercapturic acid pathway that catalyzes formation of glutathione-electrophile conjugates (GS-E). We studied 2HF in small cell (SCLC) and non-small cell (NSCLC) lung cancer cell lines for sensitivity to 2HF antineoplastic activity and to determine the role of the GS-E transporter Rlip (Ral-interacting protein; RLIP76; RALBP1) in the mechanism of action of 2HF. Our results show that 2HF induced apoptosis in both histological types of lung cancer and inhibited proliferation and growth through suppression of CDK4, CCNB1, PIK3CA, AKT and RPS6KB1 (P70S6K) signaling. Increased E-cadherin and reduced fibronectin and vimentin indicated inhibition of epithelial-mesenchymal transition. Additionally, 2HF inhibited efflux of doxorubicin and increased its accumulation in the cells, but did not add to the transport inhibitory effect of anti-Rlip antibodies alone. Binding of Rlip to 2HF was evident from successful purification of Rlip by 2HF affinity chromatography. Consistent with increased drug accumulation, combined treatment with 1-chloro-2, 4-dinitrobenzene, reduced the GI50 of 2HF by an order of magnitude. Results of in-vivo nude mouse xenograft studies of SCLC and NSCLC, which showed that orally administered 2HF inhibited growth of both histological types of lung cancer, confirmed in-vitro study results. Our result suggest that Rlip inhibition is likely a mechanism of action. Our findings are basis of proposing 2HF as therapeutic or preventative drug for lung cancer.

Abstract 5547: Glutathione-conjugate transport by RLIP76 is required for clathrin-dependent endocytosis and chemical carcinogenesis

Targeted depletion of the RALBP1 encoded 76 kDa splice variant, RLIP76, causes marked and sustained regression of human xenografts of lung, colon, prostate, and kidney cancer without toxicity in nude mouse models. We proposed that the remarkable efficacy and broad-spectrum of RLIP76-targeted therapy is because its glutathione-conjugate (GS-E) transport-activity is required for clathrin-dependent endocytosis (CDE) that regulates all ligand-receptor signaling and that RLIP76 is required not only for survival of cancer cells, but also for their very existence. We studied RLIP76 mutant proteins and the functional consequences of their expression into RLIP76−/− MEFs which identified key residues for GS-E binding in RLIP76, established the requirement of RLIP76-mediated GS-E transport for CDE and demonstrated a direct correlation between GS-E transport activities with CDE. Depletion of RLIP76 near completely blocked signaling down-stream of EGF in a CDE-dependent manner and Wnt5a signaling in a CDE-independent manner. The seminal prediction of this hypothesis, that RLIP76−/− mice will be deficient in chemical neoplasia, was confirmed. Benzo[a]pyrene, dimethylbenzanthracene and phorbol esters are ineffective in causing neoplasia in RLIP76−/−. PMA-induced skin carcinogenesis in RLIP76+/+ mouse was suppressed completely by depletion of either PKCα or RLIP76 by siRNA or antisense and could be restored by topical application of RLIP76 protein in RLIP76−/− mouse skin. Likewise, chemical pulmonary carcinogenesis was absent in female and nearly absent in male RLIP76−/− mice. In RLIP76−/− mice, p53, p38, and JNK activation did not occur in response to either carcinogen. Our findings demonstrate a fundamental role of RLIP76 in chemical carcinogenesis. (Supported in part by NIH grant CA 77495 (SA), CA 155350, Cancer Research Foundation of North Texas, and Institute for Cancer Research & the Joe & Jessie Crump Fund for Medical Education (SS))

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5547. doi:10.1158/1538-7445.AM2011-5547

Abstract 3702: 2-Hydroxyflavanone inhibits renal cancer growth by inhibiting tumor cell proliferation and angiogenesis

Renal cell carcinoma (RCC) is one of the top ten cancers prevalent in USA. Loss-of-function mutation in the VHL is an established risk factor for RCC contributing to 75% of total reported cases of RCC. Loss of VHL leads to highly vascularized phenotype of renal tumors. Intake of oranges has been proven to reduce the risk of RCC in multi-center international clinical trials. Hence, we studied effects of 2HF, an active anti-cancer compound of oranges, in VHL- mutant RCC. Our in vitro investigations revealed that 2HF selectively inhibits VHL-mutant RCC by inhibiting EGFR signaling which is increased due to VHL mutations in RCC. Our results also revealed for the first time, that 2HF inhibits GSTπ activity. 2HF inhibited cyclin B1 and CDK4, and induced G2/M phase arrest in VHL-mutant RCC. Importantly, 2HF inhibited the angiogenesis in VHL-mutant RCC by decreasing VEGF expression. Our in vivo studies in mice xenografts confirmed our in vitro results as evident by decreased levels of proliferation marker, Ki67 and angiogenic marker CD31, in 2HF treated (0.01%, w/w) mice xenografts of VHL-mutant RCC. 2HF also increased the expression of E-cadherin in VHL-mutant RCC which would be of significance in restoring the normal epithelial phenotype. Collectively, our in vitro and in vivo results revealed the potent anti-proliferative and anti-angiogenic effects of 2HF in VHL-mutant RCC, sparing normal cells, which could have significant implications not only in the specific management of VHL-mutant RCC but also in treating other VHL syndromes with highly vascularized phenotype.

(Supported in part by NIH grant CA 77495 (SA), CA 155350, Cancer Research Foundation of North Texas, and Institute for Cancer Research & the Joe & Jessie Crump Fund for Medical Education (SSS))

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3702. doi:10.1158/1538-7445.AM2011-3702

Abstract 4210: Gsta4 modifies susceptibility to skin tumor development in mice and humans

The incidence of non-melanoma skin cancer (NMSC) is equivalent to that of all other human cancers combined, and genetic factors contribute to risk of the disease. Using genetic crosses of skin tumor promotion sensitive DBA/2 mice with relatively resistant C57BL/6 mice, loci that modify susceptibility to tumor promotion by 12-O-tetradecanoylphorbol-13-acetate (TPA) have been mapped to chromosomes (chr) 1, 2, 9, and 19. Here, we show that Glutathione S-transferase alpha 4 (Gsta4), which maps to skin tumor promotion susceptibility locus Psl1.2 on chr 9, was expressed at significantly different levels in the epidermis of C57BL/6 versus DBA/2 mice following treatment with diverse promoting agents. Gsta4 expression was dramatically upregulated in the epidermis of C57BL/6 mice, but not DBA/2 mice, following treatment with TPA, okadaic acid, chrysarobin, or ultraviolet light. Gsta4 deficient mice were more susceptible to skin tumor development in the two-stage skin carcinogenesis protocol providing compelling evidence that Gsta4 underlies the effect of Psl1.2 on susceptibility to skin tumor promotion by TPA. A number of polymorphisms were detected in the putative promoter region of Gsta4 in C57BL/6 versus DBA/2 mice, and ongoing studies are addressing the genetic basis of strain-specific expression of Gsta4 during tumor promotion. Finally, inheritance of polymorphisms in GSTA4 was associated with risk of NMSC in human populations, further supporting Gsta4/GSTA4 as a gene that modifies susceptibility to skin tumor development. Supported by NIH grant ES016623.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4210.