Advantage of POLARx over ARCTIC FRONT ADVANCE PRO during pulmonary vein isolation for paroxysmal atrial fibrillation

Introduction

The electrical pulmonary vein (PV) isolation has been established as a curative therapy for paroxysmal atrial fibrillation (AF). Arctic Front™cryoballoon has been used worldwide for AF cryoablation. Recently, a new cryoballoon, POLARxTM CRYOABLATION system have been introduced, of which material of the balloon is softer and the N2O gas flow rate is higher.

Purpose

The aim was to investigate the procedural parameter and efficacy of POLARx comparing with Arctic Front.

Methods

This retrospective single center study included 101 consecutive patients who underwent paroxysmal AF ablation using cryoballoon at Keio University hospital from April 2021 to March 2022. The procedural data including the cryoballoon temperature and the number and duration of cryoablation were compared between POLARx (POLARx group) and ARCTIC FRONT ADVANCE PRO (AFA group). After the cryoablation, we added the radiofrequency application in order to maximize the isolated area when the voltage was remained inside PV (Figure 1). The necessities of the additional radiofrequency applications were also compared.

Results

In the present study, 64 patients in AFA group and 37 patients in POLARx group were analyzed. POLARx group included younger population and less females (62.8±9.9 vs 67.5±9.4 year of age, P=0.02; 13.5 vs 32.8%, P=0.04). There was no significant difference in comorbidities and examination data such as left atrium diameter or brain natriuretic peptide level. The minimal cryoballoon temperatures reached in POLARx group were lower than AFA group (−59.3±6.2 vs −47.7±7.5°C, P<0.01). No difference was found in the total number and duration of cryoablation and the time to isolate PV (6.1±2.1 vs 5.9±1.6, P=0.69; 790.2±256.1 vs 776.1±235.0 sec, P=0.69; 41.8±21.3 vs 47.1±29.6 sec, P=0.44, respectively). With regard to individual PVs, the total number and duration were tended to be larger at right superior PV in POLARx group (1.9±1.1 vs 1.4±0.7, P=0.01; 231.8±123.8 vs 193.2±83.0 sec, P=0.07), while there was no significant difference at the other PVs. The rate of successful PV isolation by a single cryo-application was not different between AFA and POLARx group (54.3 vs 61.4%, P=0.17). The additional radiofrequency applications were more frequent in AFA group (14.8 vs. 4.9%, P=0.003). There was a significant difference at right inferior PV (32.8 vs 8.1%, P=0.01), while not at left superior PV, left inferior PV and right superior PV (9.4 vs 2.9%, P=0.42; 9.4 vs 5.7%, P=0.71; 7.8 vs 2.7%, P=0.41). Phrenic nerve injury was occurred 1 case in both group and esophageal ulcer was occurred in 1 case in AFA group. No other complication including cardiac tamponade was occurred.

Conclusion

The total number and duration of cryoablation were not significantly different between AFA and POLARx group, except for right superior PV. There was an advantage in largely isolating right inferior PV in POLARx group comparing with AFA group.

Funding Acknowledgement

Type of funding sources: None.

Tumor rejection by disturbing tumor stroma cell interactions

The stroma of solid tumors is a complex network of different cell types. We analyzed stroma cell interactions in two tumor models during cyclophosphamide (Cy)-induced tumor rejection. In growing tumors, tumor infiltrating macrophages (TIMs) produced interleukin (IL)-10. Beginning 6 h after Cy-treatment T cells in the tumor were inactivated and TIMs switched to interferon (IFN)-gamma production. Both, IL-10 production before and IFN-gamma production after Cy-treatment by TIMs required T cells. With the same kinetics as TIMs started to produce IFN-gamma the tumor vasculature was destroyed which required IFN-gamma receptor expression on host but not tumor cells. These events preceded hemorrhagic necrosis and residual tumor cell elimination by T cells. Together, T cells regulate the function of TIMs and tumor rejection can be induced by disturbing the stroma network.

Terminal deoxynucleotidyltransferase is negatively regulated by direct interaction with proliferating cell nuclear antigen

BACKGROUND

The repertoires of Ig and TcR are generated by a combinatorial rearrangement of variable (V), diversity (D), and joining (J) segments (V(D)J recombination) in B- and T-cells. Terminal deoxynucleotidyltransferase (TdT) adds extra nucleotides (N nucleotides) at the junctions of the gene segments to enhance the Ig and TcR genes diversity. Using an anti-TdT antibody column, TdT has been purified as a member of a megadalton protein complex from rat thymus. The N region would be synthesized with the large protein complex.

RESULTS

The cDNAs for proliferating cell nuclear antigen (PCNA) were isolated by yeast two-hybrid screening as the gene products which directly interacted with TdT. The interaction between PCNA and TdT was confirmed by co-immunoprecipitation, both in vitro and in vivo. TdT binds directly to a PCNA trimer, as shown by gel filtration. TdT interacts with PCNA in its DNA polymerization domain (DPD), but not in its BRCA-1 C-terminal (BRCT) domain. TdT activity was reduced to 17% of the maximum value by TdT/PCNA complex formation.

CONCLUSION

TdT interacts directly with PCNA through its DPD. A functional consequence of this interaction is the negative regulation of TdT activity. These findings suggest that TdT catalyses the addition of N nucleotides under the negative control of PCNA during V(D)J recombination.

Terminal deoxynucleotidyltransferase directly interacts with a novel nuclear protein that is homologous to p65

BACKGROUND

Terminal deoxynucleotidyltransferase (TdT) is a DNA polymerase that enhances Ig and TcR gene diversity in the N region in B- and T-cells. TdT is found as a member of a large protein complex in the lysate of the thymocytes. To elucidate the molecular mechanism of the synthesis of the N region, we first attempted to isolate the genes with products that are interacting directly with TdT.

RESULTS

Using a yeast two-hybrid system, we isolated a cDNA clone encoding a novel nuclear protein that interacts with TdT. This protein was designated as TdT interacting factor 1 (TdIF1). TdIF1 has a high degree of homology to the transcription factor p65, which belongs to the nuclear receptor superfamily. TdIF1 contains HMG-I and HMG-Y DNA binding domains (AT-hooks) and can bind to single- and double-stranded DNA. TdT and TdIF1 were co-eluted at position 232 kDa by gel filtration of MOLT4 lysate. TdIF1 can enhance TdT activity fourfold in vitro assay system using oligo(dT)16 as primers.

CONCLUSIONS

TdIF1 binds directly to TdT, both in vitro and in vivo. TdIF1 and TdT exist as the members of a 232 kDa protein complex. TdIF1 can enhance TdT activity maximum fourfold in vitro assay system, suggesting that it positively regulates the synthesis of the N region during V(D)J recombination in the Ig and TcR genes.

T helper cell type 1-associated and cytotoxic T lymphocyte-mediated tumor immunity is impaired in interleukin 4-deficient mice

It is widely accepted that cellular immune responses are induced by CD4(+) T helper 1 (Th1) cells secreting interleukin (IL)-2 and interferon (IFN)-gamma. Tumor immunity is often mediated by cytotoxic T lymphocytes (CTLs) whose activation is supported by Th1 cytokines. Since IL-4 directs Th2 development and has been shown to inhibit Th1-dominated responses, we assumed that IL-4-deficient (IL-4(-/-)) mice would develop vigorous CTL-mediated tumor immunity compared with IL-4-competent (IL-4(+/+)) mice. Surprisingly, IL-4(-/-) mice were severely impaired to develop tumor immunity to both a mammary adenocarcinoma line and a colon carcinoma line. The lack of tumor immunity in IL-4(-/-) mice was associated with reduced IFN-gamma production, diminished levels of tumor-reactive serum IgG2a, and undetectable CTL activity, indicating a defective Th1 response in the absence of endogenous IL-4. Anti-IL-4 monoclonal antibody blocked tumor immunity in IL-4(+/+) mice when administered at the time of immunization but not at the time of challenge. Additionally, tumor immunity could be induced in IL-4(-/-) mice, if IL-4 was provided by gene-modified cells together with immunizing tumor cells. These results demonstrate that tumor immunity requires IL-4 in the priming phase for the generation of effector cells rather than for their maintenance and exclude secondary, developmental defects in the "knockout" strain. Together, our results demonstrate a novel and previously unanticipated role of IL-4 for the generation of Th1-associated, CTL-mediated tumor immunity.

B cells inhibit induction of T cell-dependent tumor immunity

Cytotoxic T lymphocyte (CTL) mediated tumor immunity against major histocompatibility antigen (MHC) class I-positive but class II-negative tumors often requires help from CD4+ T cells. These CD4 cells are activated by MHC class II-positive cells that present tumor derived antigens. Considering that different antigen presenting cells, such as B cells, macrophages and dendritic cells compete for antigen and influence the outcome of an immune response, we analyzed tumor immunity in B cell-deficient mice. These mice appear normal with regard to T cell immunity and tolerance to some pure foreign antigens. We show here that the low immunogenicity of tumors is caused by B cells whose presence in the priming phase results in disabled CD4+ T cell help for CTL mediated tumor immunity. Instead, in the presence of B cells, a non-protective humoral immune response is induced. Our results may explain the enigmatic observation that tumor-reactive antibodies occur frequently in cancer patients.