An Expedited Transition to the Back Wall Suturing for Side-to-Side In Situ Microvascular Anastomosis: A Technique Update.

BACKGROUND: The side-to-side in situ microvascular anastomosis is an important tool in the cerebrovascular neurosurgeon's armamentarium. The execution of the side-to-side anastomosis, however, can be limited by the inability to acquire sufficient visualization and approximation of the recipient and donor vessels. OBJECTIVE: To expedite the transition to the back wall suturing of the donor and recipient vessels during side-to-side in situ microvascular anastomosis. METHODS: Incorporation of the first suture throw from the outside to the inside of the vessel lumen with the initial stay suture at the proximal apex of the arteriotomy is described. The apical knot is tied between one limb of the resultant loop and the free end of the suture. The remainder of side-to-side anastomosis can then be completed in a standard fashion starting from the inside of the lumen. RESULTS: This modification allows for an expedited transition to the back wall suturing of the 2 arterial segments and avoids difficulties associated with taking the first bite from behind the knot at the proximal apex of the arteriotomy or the transfer of the needle between the approximated vessels. This updated technique is illustrated with a case example, illustration, and video. CONCLUSION: This technical modification for the side-to-side anastomosis helps optimize microsurgical efficiency by limiting needle, suture, and vessel handling after the initial suture placement, which has classically been a challenge of this bypass.

Mitochondrial dysfunction RAD51, and Ku80 proteolysis promote apoptotic effects of Dinaciclib in Bcl-xL silenced cells.

In the present study, we investigated the effect of CDK inhibitors (ribociclib, palbociclib, seliciclib, AZD5438, and dinaciclib) on malignant human glioma cells for cell viability, apoptosis, oxidative stress, and mitochondrial function using various assays. None of the CDK inhibitors induced cell death at a clinically relevant concentration. However, low nanomolar concentrations of dinaciclib showed higher cytotoxic activity against Bcl-xL silenced cells in a time- and concentration-dependent manner. This effect was not seen with other CDK inhibitors. The apoptosis-inducing capability of dinaciclib in Bcl-xL silenced cells was evidenced by cell shrinkage, mitochondrial dysfunction, DNA damage, and increased phosphatidylserine externalization. Dinaciclib was found to disrupt mitochondrial membrane potential, resulting in the release of cytochrome c, AIF, and smac/DIABLO into the cytoplasm. This was accompanied by the downregulation of cyclin-D1, D3, and total Rb. Dinaciclib caused cell cycle arrest in a time- and concentration-dependent manner and with accumulation of cells in the sub-G1 phase. Our results also revealed that dinaciclib, but not ribociclib or palbociclib or seliciclib or AZD5438 induced intrinsic apoptosis via upregulation of the levels of pro-apoptotic proteins (Bax and Bak), resulting in the activation of caspases and cleavage of PARP. We also found an additional mechanism for the dinaciclib-induced augmentation of apoptosis due to abrogation RAD51-cyclin D1 interaction, specifically proteolysis of the DNA repair proteins RAD51 and Ku80. Our results suggest that successfully interfering with Bcl-xL function may restore sensitivity to dinaciclib and could hold the promise for an effective combination therapeutic strategy.

Survivin inhibitor YM155 induces mitochondrial dysfunction, autophagy, DNA damage and apoptosis in Bcl-xL silenced glioma cell lines.

Because the anti-apoptotic protein Bcl-xL is overexpressed in glioma, one might expect that inhibiting or silencing this gene would promote tumor cell killing. However, our studies have shown that this approach has limited independent activity, but may tip the balance in favor of apoptosis induction in response to other therapeutic interventions. To address this issue, we performed a pharmacological screen using a panel of signaling inhibitors and chemotherapeutic agents in Bcl-xL silenced cells. Although limited apoptosis induction was observed with a series of inhibitors for receptor tyrosine kinases, PKC inhibitors, Src family members, JAK/STAT, histone deacetylase, the PI3K/Akt/mTOR pathway, MAP kinase, CDK, heat shock proteins, proteasomal processing, and various conventional chemotherapeutic agents, we observed a dramatic potentiation of apoptosis in Bcl-xL silenced cells with the survivin inhibitor, YM155. Treatment with YM155 increased the release of cytochrome c, smac/DIABLO and apoptosis inducing-factor, and promoted loss of mitochondrial membrane potential, activation of Bax, recruitment of LC3-II to the autophagosomes and apoptosis in Bcl-xL silenced cells. We also found an additional mechanism for the augmentation of apoptosis due to abrogation of DNA double-strand break repair mediated by Rad51 repression and enhanced accumulation of γH2AX. In summary, our observations may provide a new insight into the link between Bcl-xL and survivin inhibition for the development of novel therapies for glioma. © 2016 Wiley Periodicals, Inc.

Dinaciclib, a Cyclin-Dependent Kinase Inhibitor Promotes Proteasomal Degradation of Mcl-1 and Enhances ABT-737-Mediated Cell Death in Malignant Human Glioma Cell Lines.

The prognosis for malignant glioma, the most common brain tumor, is still poor, underscoring the need to develop novel treatment strategies. Because glioma cells commonly exhibit genomic alterations involving genes that regulate cell-cycle control, there is a strong rationale for examining the potential efficacy of strategies to counteract this process. In this study, we examined the antiproliferative effects of the cyclin-dependent kinase inhibitor dinaciclib in malignant human glioma cell lines, with intact, deleted, or mutated p53 or phosphatase and tensin homolog on chromosome 10; intact or deleted or p14ARF or wild-type or amplified epidermal growth factor receptor. Dinaciclib inhibited cell proliferation and induced cell-cycle arrest at the G2/M checkpoint, independent of p53 mutational status. In a standard 72-hour 3-[4,5-dimethylthiazol- 2yl]-5-[3-carboxymethoxyphenyl]-2-[4-sulfophenyl]-2H, tetrazolium (MTS) assay, at clinically relevant concentrations, dose-dependent antiproliferative effects were observed, but cell death was not induced. Moreover, the combination of conventional chemotherapeutic agents and various growth-signaling inhibitors with dinaciclib did not yield synergistic cytotoxicity. In contrast, combination of the Bcl-2/Bcl-xL inhibitors ABT-263 (4-[4-[[2-(4-chlorophenyl)-5,5-dimethylcyclohexen-1-yl]methyl]piperazin-1-yl]-N-[4-[[(2R)-4-morpholin-4-yl-1-phenylsulfanylbutan-2-yl]amino]-3-(trifluoromethylsulfonyl)phenyl]sulfonylbenzamide) or ABT-737 (4-[4-[[2-(4-chlorophenyl)phenyl]methyl]piperazin-1-yl]-N-[4-[[(2R)-4-(dimethylamino)-1-phenylsulfanylbutan-2-yl]amino]-3-nitrophenyl]sulfonylbenzamide) with dinaciclib potentiated the apoptotic response induced by each single drug. The synergistic killing by ABT-737 with dinaciclib led to cell death accompanied by the hallmarks of apoptosis, including an early loss of the mitochondrial transmembrane potential; the release of cytochrome c, smac/DIABLO, and apoptosis-inducing factor; phosphatidylserine exposure on the plasma membrane surface and activation of caspases and poly ADP-ribose polymerase. Mechanistic studies revealed that dinaciclib promoted proteasomal degradation of Mcl-1. These observations may have important clinical implications for the design of experimental treatment protocols for malignant human glioma.