Alternative splicing of its 5'-UTR limits CD20 mRNA translation and enables resistance to CD20-directed immunotherapies

Aberrant skipping of coding exons in CD19 and CD22 compromises the response to immunotherapy in B-cell malignancies. Here, we showed that the MS4A1 gene encoding human CD20 also produces several messenger RNA (mRNA) isoforms with distinct 5' untranslated regions. Four variants (V1-4) were detected using RNA sequencing (RNA-seq) at distinct stages of normal B-cell differentiation and B-lymphoid malignancies, with V1 and V3 being the most abundant. During B-cell activation and Epstein-Barr virus infection, redirection of splicing from V1 to V3 coincided with increased CD20 positivity. Similarly, in diffuse large B-cell lymphoma, only V3, but not V1, correlated with CD20 protein levels, suggesting that V1 might be translation-deficient. Indeed, the longer V1 isoform contained upstream open reading frames and a stem-loop structure, which cooperatively inhibited polysome recruitment. By modulating CD20 isoforms with splice-switching morpholino oligomers, we enhanced CD20 expression and anti-CD20 antibody rituximab-mediated cytotoxicity in a panel of B-cell lines. Furthermore, reconstitution of CD20-knockout cells with V3 mRNA led to the recovery of CD20 positivity, whereas V1-reconstituted cells had undetectable levels of CD20 protein. Surprisingly, in vitro CD20-directed chimeric antigen receptor T cells were able to kill both V3- and V1-expressing cells, but the bispecific T-cell engager mosunetuzumab was only effective against V3-expressing cells. To determine whether CD20 splicing is involved in immunotherapy resistance, we performed RNA-seq on 4 postmosunetuzumab follicular lymphoma relapses and discovered that in 2 of them, the downregulation of CD20 was accompanied by a V3-to-V1 shift. Thus, splicing-mediated mechanisms of epitope loss extend to CD20-directed immunotherapies.

Alternative splicing of its 5'-UTR limits CD20 mRNA translation and enables resistance to CD20-directed immunotherapies

Aberrant skipping of coding exons in CD19 and CD22 compromises responses to immunotherapy for B-cell malignancies. Here, we show that the MS4A1 gene encoding human CD20 also produces several mRNA isoforms with distinct 5' untranslated regions (5'-UTR). Four variants (V1-4) were detectable by RNA-seq in distinct stages of normal B-cell differentiation and B-lymphoid malignancies, with V1 and V3 being the most abundant by far. During B-cell activation and Epstein-Barr virus infection, redirection of splicing from V1 to V3 coincided with increased CD20 positivity. Similarly, in diffuse large B-cell lymphoma only V3, but not V1, correlated with CD20 protein levels, suggesting that V1 might be translation-deficient. Indeed, the longer V1 isoform was found to contain upstream open reading frames (uORFs) and a stem-loop structure, which cooperatively inhibited polysome recruitment. By modulating CD20 isoforms with splice-switching Morpholino oligomers, we enhanced CD20 expression and anti-CD20 antibody rituximab-mediated cytotoxicity in a panel of B-cell lines. Furthermore, reconstitution of CD20-knockout cells with V3 mRNA led to the recovery of CD20 positivity, while V1-reconstituted cells had undetectable levels of CD20 protein. Surprisingly, in vitro CD20-directed CAR T cells were able to kill both V3- and V1-expressing cells, but the bispecific T cell engager mosunetuzumab was only effective against V3-expressing cells. To determine whether CD20 splicing is involved in immunotherapy resistance, we performed RNA-seq on four post-mosunetuzumab follicular lymphoma relapses and discovered that in two of them downregulation of CD20 was accompanied by the V3-to-V1 shift. Thus, splicing-mediated mechanisms of epitope loss extend to CD20-directed immunotherapies.

Key Points

In normal & malignant human B cells, CD20 mRNA is alternatively spliced into four 5'-UTR isoforms, some of which are translation-deficient.The balance between translation-deficient and -competent isoforms modulates CD20 protein levels & responses to CD20-directed immunotherapies.

Explanation of Novelty

We discovered that in normal and malignant B-cells, CD20 mRNA is alternatively spliced to generate four distinct 5'-UTRs, including the longer translation-deficient V1 variant. Cells predominantly expressing V1 were still sensitive to CD20-targeting chimeric antigen receptor T-cells. However, they were resistant to the bispecific anti-CD3/CD20 antibody mosunetuzumab, and the shift to V1 were observed in CD20-negative post-mosunetuzumab relapses of follicular lymphoma.

Potent preclinical activity of FLT3-directed chimeric antigen receptor T-cell immunotherapy against FLT3- mutant acute myeloid leukemia and KMT2A-rearranged acute lymphoblastic leukemia

Chimeric antigen receptor (CAR) T-cell immunotherapies targeting CD19 or CD22 induce remissions in the majority of patients with relapsed/refractory B-cell acute lymphoblastic leukemia (ALL), although relapse due to target antigen loss or downregulation has emerged as a major clinical dilemma. Accordingly, great interest exists in developing CAR T cells directed against alternative leukemia cell surface antigens that may help to overcome immunotherapeutic resistance. The fms-like tyrosine kinase 3 receptor (FLT3) is constitutively activated via FLT3 mutation in acute myeloid leukemia (AML) or wild-type FLT3 overexpression in KMT2A (lysine-specific methyltransferase 2A)-rearranged ALL, which are associated with poor clinical outcomes in children and adults. We developed monovalent FLT3-targeted CAR T cells (FLT3CART) and bispecific CD19xFLT3CART and assessed their anti-leukemia activity in preclinical models of FLT3-mutant AML and KMT2A-rearranged infant ALL. We report robust in vitro FLT3CART-induced cytokine production and cytotoxicity against AML and ALL cell lines with minimal cross-reactivity against normal hematopoietic and non-hematopoietic tissues. We also observed potent in vivo inhibition of leukemia proliferation in xenograft models of both FLT3-mutant AML and KMT2A-rearranged ALL, including a post-tisagenlecleucel ALL-to-AML lineage switch patient-derived xenograft model pairing. We further demonstrate significant in vitro and in vivo activity of bispecific CD19xFLT3CART against KMT2Arearranged ALL and posit that this additional approach might also diminish potential antigen escape in these high-risk leukemias. Our preclinical data credential FLT3CART as a highly effective immunotherapeutic strategy for both FLT3- mutant AML and KMT2A-rearranged ALL which is poised for further investigation and clinical translation.

A Comparison of Single Fraction and Multi Fraction Radiosurgery on the Gamma Knife ICON: A Single Institution Review

Purpose

Brain metastases are a common development in patients with malignant solid tumors. Stereotactic radiosurgery (SRS) has a long track record of effectively and safely treating these patients, with some limitations to the use of single fraction SRS based on size and volume. In this study, we reviewed outcomes of patients treated using SRS and fractionated SRS (fSRS) to compare predictors and outcomes of those treatments.

Methods and Materials

Two hundred patients treated with SRS or fSRS for intact brain metastases were included. We tabulated baseline characteristics and performed a logistic regression to identify predictors of fSRS. Cox regression was used to identify predictors of survival. Kaplan-Meier analysis was used to calculate survival, local failure, and distant failure rates. A receiver operating characteristic curve was generated to determine timepoint from planning to treatment associated with local failure.

Results

The only predictor of fSRS was tumor volume >2.061 cm³. There was no difference in local failure, toxicity, or survival by fractionation of biologically effective dose. Predictors of worse survival were age, extracranial disease, history of whole brain radiation therapy, and volume. Receiver operating characteristic analysis identified 10 days as potential factor in local failure. At 1 year, local control was 96.48 and 76.92% for those patients treated before or after that interval, respectively (P = .0005).

Conclusions

Fractionated SRS is a safe and effective alternative for patients with larger volume tumors not suitable for single fraction SRS. Care should be taken to treat these patients expeditiously as a delay was shown to affect local control in this study.

Temsirolimus combined with cyclophosphamide and etoposide for pediatric patients with relapsed/refractory acute lymphoblastic leukemia: a Therapeutic Advances in Childhood Leukemia Consortium trial (TACL 2014-001)

Phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) signaling is commonly dysregulated in acute lymphoblastic leukemia (ALL). The TACL2014-001 phase I trial of the mTOR inhibitor temsirolimus in combination with cyclophosphamide and etoposide was performed in children and adolescents with relapsed/refractory ALL. Temsirolimus was administered intravenously (IV) on days 1 and 8 with cyclophosphamide 440 mg/m2 and etoposide 100 mg/m2 IV daily on days 1-5. The starting dose of temsirolimus was 7.5 mg/m2 (DL1) with escalation to 10 mg/m2 (DL2), 15 mg/m2 (DL3), and 25 mg/m2 (DL4). PI3K/mTOR pathway inhibition was measured by phosphoflow cytometry analysis of peripheral blood specimens from treated patients. Sixteen heavily-pretreated patients were enrolled with 15 evaluable for toxicity. One dose-limiting toxicity of grade 4 pleural and pericardial effusions occurred in a patient treated at DL3. Additional dose-limiting toxicities were not seen in the DL3 expansion or DL4 cohort. Grade 3/4 non-hematologic toxicities occurring in three or more patients included febrile neutropenia, elevated alanine aminotransferase, hypokalemia, mucositis, and tumor lysis syndrome and occurred across all doses. Response and complete were observed at all dose levels with a 47% overall response rate and 27% complete response rate. Pharmacodynamic correlative studies demonstrated dose-dependent inhibition of PI3K/mTOR pathway phosphoproteins in all studied patients. Temsirolimus at doses up to 25 mg/m2 with cyclophosphamide and etoposide had an acceptable safety profile in children with relapsed/refractory ALL. Pharmacodynamic mTOR target inhibition was achieved and appeared to correlate with temsirolimus dose. Future testing of next-generation PI3K/mTOR pathway inhibitors with chemotherapy may be warranted to increase response rates in children with relapsed/refractory ALL.

Activated interleukin-7 receptor signaling drives B-cell acute lymphoblastic leukemia in mice

Philadelphia chromosome-like acute lymphoblastic leukemia (Ph-like ALL) is a high-risk subtype of B-ALL often associated with genetic variants that alter cytokine receptor signaling, including mutations in the interleukin-7 receptor (IL7R). To investigate whether IL7R variants are leukemia-initiating, we built mouse models expressing activated Il7r (aIL7R). B-cell intrinsic aIL7R mice developed spontaneous B-ALL, demonstrating sufficiency of Il7r activating mutations in leukemogenesis. Concomitant introduction of a knock-out allele in the associated adapter protein Lnk (encoded by Sh2b3) or a dominant-negative variant of the transcription factor Ikaros (Ikzf1) increased disease penetrance. The resulting murine leukemias displayed monoclonality and recurrent somatic Kras mutations and efficiently engrafted into immunocompetent mice. Phosphoproteomic analyses of aIL7R leukemic cells revealed constitutive Stat5 signaling and B cell receptor (BCR)-like signaling despite the absence of surface pre-BCR. Finally, in vitro treatment of aIL7R leukemic B-cells with Jak, mTOR, or Syk inhibitors blocked growth, confirming that each pathway is active in this mouse model of IL7R-driven B-ALL.

Network Analysis Reveals Synergistic Genetic Dependencies for Rational Combination Therapy in Philadelphia Chromosome-Like Acute Lymphoblastic Leukemia

PURPOSE

Systems biology approaches can identify critical targets in complex cancer signaling networks to inform new therapy combinations that may overcome conventional treatment resistance.

EXPERIMENTAL DESIGN

We performed integrated analysis of 1,046 childhood B-ALL cases and developed a data-driven network controllability-based approach to identify synergistic key regulator targets in Philadelphia chromosome-like B-acute lymphoblastic leukemia (Ph-like B-ALL), a common high-risk leukemia subtype associated with hyperactive signal transduction and chemoresistance.

RESULTS

We identified 14 dysregulated network nodes in Ph-like ALL involved in aberrant JAK/STAT, Ras/MAPK, and apoptosis pathways and other critical processes. Genetic cotargeting of the synergistic key regulator pair STAT5B and BCL2-associated athanogene 1 (BAG1) significantly reduced leukemia cell viability in vitro. Pharmacologic inhibition with dual small molecule inhibitor therapy targeting this pair of key nodes further demonstrated enhanced antileukemia efficacy of combining the BCL-2 inhibitor venetoclax with the tyrosine kinase inhibitors ruxolitinib or dasatinib in vitro in human Ph-like ALL cell lines and in vivo in multiple childhood Ph-like ALL patient-derived xenograft models. Consistent with network controllability theory, co-inhibitor treatment also shifted the transcriptomic state of Ph-like ALL cells to become less like kinase-activated BCR-ABL1-rearranged (Ph+) B-ALL and more similar to prognostically favorable childhood B-ALL subtypes.

CONCLUSIONS

Our study represents a powerful conceptual framework for combinatorial drug discovery based on systematic interrogation of synergistic vulnerability pathways with pharmacologic inhibitor validation in preclinical human leukemia models.

Therapeutic potential of ruxolitinib and ponatinib in patients with EPOR-rearranged Philadelphia chromosome-like acute lymphoblastic leukemia

Not available.

Combinatorial efficacy of entospletinib and chemotherapy in patient-derived xenograft models of infant acute lymphoblastic leukemia

Survival of infants with KMT2A-rearranged acute lymphoblastic leukemia (ALL) remains dismal despite intensive chemotherapy. We observed constitutive phosphorylation of spleen tyrosine kinase (SYK) and associated signaling proteins in infant ALL patient-derived xenograft (PDX) model specimens and hypothesized that the SYK inhibitor entospletinib would inhibit signaling and cell growth in vitro and leukemia proliferation in vivo. We further predicted that combined entospletinib and chemotherapy could augment anti-leukemia effects. Basal kinase signaling activation and HOXA9/MEIS1 expression differed among KMT2Arearranged (KMT2A-AFF1 [n=4], KMT2A-MLLT3 [n=1], KMT2A-MLLT1 [n=4]) and non-KMT2A-rearranged [n=3] ALL specimens and stratified by genetic subgroup. Incubation of KMT2A-rearranged ALL cells in vitro with entospletinib inhibited methylcellulose colony formation and SYK pathway signaling in a dose-dependent manner. In vivo inhibition of leukemia proliferation with entospletinib monotherapy was observed in RAS-wild-type KMT2A-AFF1, KMT2A-MLLT3, and KMT2A-MLLT1 ALL PDX models with enhanced activity in combination with vincristine chemotherapy in several models. Surprisingly, entospletinib did not decrease leukemia burden in two KMT2A-AFF1 PDX models with NRAS or KRAS mutations, suggesting potential RAS-mediated resistance to SYK inhibition. As hypothesized, superior inhibition of ALL proliferation was observed in KMT2A-AFF1 PDX models treated with entospletinib and the MEK inhibitor selumetinib versus vehicle or inhibitor monotherapies (P<0.05). In summary, constitutive activation of SYK and associated signaling occurs in KMT2A-rearranged ALL with in vitro and in vivo sensitivity to entospletinib. Combination therapy with vincristine or selumetinib further enhanced treatment effects of SYK inhibition. Clinical study of entospletinib and chemotherapy or other kinase inhibitors in patients with KMT2A-rearranged leukemias may be warranted.

Abstract 3893: Novel synergistic targets for combination therapy in Philadelphia chromosome-like acute lymphoblastic leukemia

Philadelphia chromosome-like B-acute lymphoblastic leukemia (Ph-like ALL) is a common leukemia subtype associated with high relapse rates and poor overall survival. Ph-like ALL has a kinase-activated gene expression signature similar to that of BCR-ABL1-rearranged ALL, but is driven by alternative mutations in JAK or ABL kinase signaling pathway genes. Preclinical studies using tyrosine kinase inhibitor (TKI) monotherapy in Ph-like ALL models demonstrate incomplete efficacy, emphasizing the need for combination therapy to improve cure rates. In these studies, we use a novel patient ‘omics data-driven approach to nominate pathways for optimal synergistic targeting in Ph-like ALL. We utilized our OptiCon algorithm (Hu et al. Nat. Comm. 2019) to analyze publicly-available genomic and transcriptomic data from patient leukemia samples. We identified synergistic gene pairs that control a maximal number of deregulated genes (for optimal efficacy) and a minimal number of unperturbed genes (to minimize toxicity) in Ph-like ALL, including a top-ranked synergistic control pair STAT5B and BAG1. STAT5B is hyperactive in different subclasses of Ph-like ALL and BAG1 (BCL2-associated athanogene1) enhances the anti-apoptotic effect of BCL-2 likely via degradation prevention. We then validated the anti-leukemic efficacy of co-targeting this pairing in Ph-like ALL cell lines and patient-derived xenograft (PDX) models. We assessed the in vitro and in vivo effects of combining the BCL-2 inhibitor venetoclax with the JAKi ruxolitinib or ABL1i dasatinib in 3 Ph-like ALL cell lines (CRLF2-rearranged/JAK-mutant MUTZ5 and MHH-cALL-4, immortalized ABL1-rearranged TVA-1) and 3 Ph-like ALL PDX models (CRLF2-rearranged/JAK-mutant ALL4364 and UP_ALL4988, ABL1-rearranged TVA-1). Co-treatment of the 3 cell lines with venetoclax and ruxolitinib or dasatinib showed synergy at all dose combinations tested, versus monotherapy (CI &lt;1.0). Venetoclax and ruxolitinib co-treatment of UP_ALL4988 and ALL4364 PDX mice significantly inhibited leukemia proliferation in vivo when compared to vehicle or single-agent inhibitors. Similar findings were observed in TVA-1 PDX mice treated with venetoclax and dasatinib. These preclinical results provide compelling rationale for potential combination therapy using BCL-2 inhibitor with TKIs in treatment of patients with Ph-like ALL, and represent an unbiased approach to the identification and testing of synergistic targets as candidates for multi-agent precision medicine therapy.

Citation Format: Yang Y. Ding, Kellyn Madden, Joseph P. Loftus, Hannah Kim, Chia-hui Chen, Sarah K. Tasian, Kai Tan. Novel synergistic targets for combination therapy in Philadelphia chromosome-like acute lymphoblastic leukemia [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3893.

Oncogene-independent BCR-like signaling adaptation confers drug resistance in Ph-like ALL

Children and adults with Philadelphia chromosome-like B cell acute lymphoblastic leukemia (Ph-like B-ALL) experience high relapse rates despite best-available conventional chemotherapy. Ph-like ALL is driven by genetic alterations that activate constitutive cytokine receptor and kinase signaling, and early-phase trials are investigating the potential of the addition of tyrosine kinase inhibitors (TKIs) to chemotherapy to improve clinical outcomes. However, preclinical studies have shown that JAK or PI3K pathway inhibition is insufficient to eradicate the most common cytokine receptor-like factor 2-rearranged (CRLF2-rearranged) Ph-like ALL subset. We thus sought to define additional essential signaling pathways required in Ph-like leukemogenesis for improved therapeutic targeting. Herein, we describe an adaptive signaling plasticity of CRLF2-rearranged Ph-like ALL following selective TKI pressure, which occurs in the absence of genetic mutations. Interestingly, we observed that Ph-like ALL cells have activated SRC, ERK, and PI3K signaling consistent with activated B cell receptor (BCR) signaling, although they do not express cell surface μ-heavy chain (μHC). Combinatorial targeting of JAK/STAT, PI3K, and "BCR-like" signaling with multiple TKIs and/or dexamethasone prevented this signaling plasticity and induced complete cell death, demonstrating a more optimal and clinically pragmatic therapeutic strategy for CRLF2-rearranged Ph-like ALL.

The effects of baicalein on canine osteosarcoma cell proliferation and death

Flavonoids are a group of modified triphenolic compounds from plants with medicinal properties. Baicalein, a specific flavone primarily isolated from plant roots (Scutellaria baicalensis), is commonly used in Eastern medicine for its anti-inflammatory and antineoplastic properties. Previous research shows greater efficacy for baicalein than most flavonoids; however, there has been little work examining their effects on sarcoma cells, let alone canine cells. Three canine osteosarcoma cell lines (HMPOS, D17 and OS 2.4) were treated with baicalein to examine cell viability, cell cycle kinetics, anchorage-independent growth and apoptosis. Results showed that osteosarcoma cells were sensitive to baicalein at concentrations from approximately 1 to 25 μM. Modest cell cycle changes were observed in one cell line. Baicalein was effective in inducing apoptosis and did not prevent doxorubicin cell proliferation inhibition in all the cell lines. The mechanism for induction of apoptosis has not been fully elucidated; however, changes in mitochondrial permeability supersede the apoptotic response.

Laminar xanthine oxidase, superoxide dismutase and catalase activities in the prodromal stage of black-walnut induced equine laminitis

REASONS FOR STUDY: Xanthine oxidase (XO)-dependent production of superoxide anion and hydrogen peroxide, a characteristic of ischaemia-reperfusion injury, may contribute to the development of equine laminitis.

OBJECTIVE

To determine the levels of XO and antioxidant enzymes (catalase, superoxide dismutase [SOD]) in the digital laminae of normal horses (CON) and horses in the developmental stage of laminitis using the black walnut extract (BWE) model.

METHODS

Healthy horses (n = 12) were administered BWE (BWE group, n = 6), or water (CON group, n = 6) through a nasogastric tube. At the onset of leucopenia in the BWE-treated animals, all horses were anaesthetised, digital laminae and other samples collected rapidly and flash frozen, and the animals subjected to euthanasia. Extracts of the frozen tissues were assayed for the 2 conformational forms of xanthine: oxygen oxidoreductase (XOR), namely, xanthine dehydrogenase (XDH) and xanthine oxidase (XO), as well as the antioxidant enzymes, SOD and catalase.

RESULTS

Extracts of liver, lungs and skin, but not digital laminae, from either CON or BWE-treated horses had endogenous SOD, whereas all had endogenous XO and catalase. The levels of XDH, XO and catalase were similar in extracts of laminae from CON and BWE-treated horses as was the ratio of XDH to XO in extracts.

CONCLUSIONS AND POTENTIAL RELEVANCE

The absence of increased XO activity suggest against the involvement of this reactive oxygen intermediate-generating system in the development of laminar pathology in BWE-treated horses. Conversely, the absence of SOD from extracts of equine digital laminae, but not other tissues, suggests that the equine digital laminae are highly susceptible to damage by superoxide anion, produced, for example, by emigrant inflammatory leucocytes.

Tissue concentrations of 4-HNE in the black walnut extract model of laminitis: indication of oxidant stress in affected laminae

In the septic horse prone to laminitis, a similar activation of the innate immune system appears to occur as reported in the septic human prone to organ failure. Because oxidant injury plays a central role in organ failure occurring due to an overzealous innate immune response in human sepsis, this study was performed to determine whether there was evidence of oxidant stress in the laminar tissue in the early stages of laminitis. 4-Hydroxy-2-nonenal (4-HNE), a lipid aldehyde that forms due to lipid peroxidation occurring during episodes of oxidant stress, readily forms adducts with cellular proteins; these adducts can be assessed as a marker of oxidant stress in the form of lipid peroxidation. In this study, a slot blot technique was used to assess 4-HNE adduct concentrations in the laminae, lung, liver, and intestinal tract in the black walnut extract (BWE) model of laminitis. Significant increases in laminar 4-HNE adduct concentrations were identified at two early stages in the BWE model, in the absence of such changes in the other tissues. These data indicate that oxidant stress may play an important role in the laminar failure in laminitis, and further support the concept that a poor antioxidant response in the laminae relative to other equine tissues may be responsible for failure of the laminae in the septic horse. In contrast, tissues such as the lung and liver that undergo oxidant injury in human sepsis appear to be relatively protected in horses.

A comparison of the effects of lamotrigine on neuroma-induced action potential firing and normal behaviour in rat: implications for establishing a pre-clinical 'therapeutic index'

The effects of lamotrigine on rat neuroma and behavioural paradigms were evaluated to determine a pre-clinical therapeutic index. Lamotrigine blocked neuroma-induced burst pattern firing at a free plasma concentration of 13.7+/-1.7 microM (n=5). Oral dosing of lamotrigine (50-200 mg/kg) had no significant effects on behaviour but measurements of plasma concentrations of free drug showed non-linear oral absorption and lower than predicted drug levels (5-27 microM). Given intravenously (10-100 mg/kg), lamotrigine did affect behaviour at a free plasma concentration of 42.0 microM (n=2). By comparing free plasma concentrations, a therapeutic index of 3 was calculated, which is lower than published data based on comparing oral doses. We propose that a therapeutic index should only be derived with reference to plasma drug concentrations to prevent non-linear or incomplete drug absorption from confounding accurate estimation.

Carotid endarterectomy: a comparison of regional versus general anesthesia in 500 operations

The outcomes of 489 patients undergoing 500 carotid endarterectomies were reviewed to compare results from using general anesthesia with those from using regional (cervical block) anesthesia. From September 1982 to May 1998, 228 procedures (221 patients) were performed under general anesthesia and 272 procedures (268 patients) were performed under local anesthesia. A detailed comparison of the two groups revealed close similarity in age, sex, presenting symptoms, and associated risk factors. Overall, perioperative mortality was 0.8%. In comparison to regional anesthesia, the general anesthesia group had greater overall morbidity (23.3 vs. 13. 6%, p < 0.008) and more frequent use of postoperative vasoactive drugs to control blood pressure (40.4 vs. 26.1%, p < 0.001). Furthermore, anesthesia time, operative time, and frequency of shunt use were significantly greater in the general anesthesia group (p < 0.03).

Trends in morbidity and mortality of hepatic resection for malignancy. A matched comparative analysis

OBJECTIVE

The authors define more clearly the trends in morbidity and mortality after hepatic resection for malignant disease in matched patient groups during two discrete time periods.

SUMMARY BACKGROUND DATA

Recent reports have shown improvement in operative morbidity and mortality associated with hepatic resection; however, results often included resections for benign disease and trauma. Furthermore, specific factors contributing to the improvement in operative risks between the last two decades have not been defined.

METHODS

A retrospective matched comparative analysis was conducted of patients with primary and metastatic hepatic malignancy resected with curative intent between two periods (1976 to 1980 and 1986 to 1990). Eighty-one patients met our inclusion criteria in the early period; this group was matched with 81 patients from the latter period by the following four parameters: age, gender, type of malignant disease, and extent of resection. Records of these two patient groups were abstracted for clinical presentation, co-morbid factors, operative techniques, and perioperative morbidity and mortality.

RESULTS

The authors found a significant decrease in operative morbidity, median perioperative transfusion, and length of hospital stay in the latter period (1986 to 1990). The incidence of postoperative subphrenic abscess and intra-abdominal hemorrhage was significantly lower during this period. Operative mortality rate was similar for both periods, 4.9% and 1.2%, respectively (p > 0.05).

CONCLUSION

Hepatic resection for malignant disease currently can be performed with a low morbidity and mortality in the hands of trained and experienced hepatic surgeons; operative risks of hepatic resection should not deter its application in the treatment of primary and metastatic malignant disease of the liver.

Sinistral portal hypertension. Splenectomy or expectant management

Splenectomy has been considered the treatment of choice for patients with bleeding from sinistral portal hypertension (SPH) and varices, but is controversial for asymptomatic patients. To further define the role of splenectomy for SPH, the authors compared the clinical presentations and outcomes of 25 patients treated with splenectomy with those of 12 observed patients. Clinical features were similar except for transfusions administered (60% vs. 25%, p < 0.05), hemoglobin (9.8 +/- 2.2 g/dL vs. 12.5 +/- 2.1 g/dL, p < 0.05), and history of prior bleeding episodes (56% vs. 8%, p < 0.05), splenectomy versus no splenectomy, respectively. At 3 years, neither survival (78% vs. 64%, p = 1.0) nor new or recurrent bleeding (16% vs. 24%, p = 0.2) differed, splenectomy versus no splenectomy, respectively. The authors conclude that in the absence of prior bleeding episodes, anemia, or severe hemorrhage, observation of patients with SPH is justified.

Atrial natriuretic factor inhibits hypertonic saline-mediated decreases in renal hemodynamics

The present study in the anesthetized dogs was designed to test the hypothesis that atrial natriuretic factor (ANF) attenuates whole kidney tubuloglomerular feedback (TGF) mediated decreases in renal blood flow (RBF) and glomerular filtration rate (GFR) produced by hypertonic saline (HS). Secondly, as adenosine (AD) has been implicated as a metabolic mediator of TGF, we also hypothesized that ANF would antagonize the renal actions of AD. To test this hypothesis, RBF and GFR were assessed in response to hypertonic saline (HS, 16%, i.r.) or adenosine (AD, 0.1 mumol/min, i.r.) in the presence and absence of exogenous ANF (100 ng/kg/min, i.r.). ANF attenuated HS-mediated reductions in GFR (HS, -39.6 +/- 9.8 ml/min vs. HS + ANF, -14.3 +/- 4.5 ml/min, P less than 0.05) and in RBF (HS, -143 +/- 35 ml/min vs. HS + ANF, -5 +/- 22 ml/min, P less than 0.05). GFR was reduced by AD (-9.2 +/- 3.0 ml/min, P less than 0.05), but maintained by AD + ANF (-0.4 +/- 2.0 ml/min, NS). A transient adenosine-mediated vasoconstriction was attenuated by ANF (AD, -54.5 +/- 3.6 ml/min vs. AD + ANF, -3.7 +/- 3.1 ml/min, P less than 0.005). We conclude that ANF at pharmacologic concentrations attenuates at the whole kidney level hypertonic saline and adenosine-mediated reductions in RBF and GFR.

Space: exploration-exploitation and the role of man

The early years of space activity have emphasized a crew role similar to that of the test pilot or the crew of a high performance aircraft; even the Apollo lunar exploration missions were dominated by the task of getting to and from the moon. Skylab was a prototype space station and began to indicate the range of other functional roles man will play in space. The operation of the Space Shuttle has the elements of the operation of any other high performance flight vehicle during launch and landing; but in its on-orbit operations, it is often a surrogate space station, developing techniques and demonstrating the role of a future space station in various functions. In future space systems, the role of the crew will encompass all of the activities pursued in research laboratories, manufacturing facilities, maintenance shops, and construction sites. The challenge will be to design the tasks and the tools so that the full benefit of the opportunities offered by performing these functions in space can be attained.