Enhancing anti-AML activity of venetoclax by isoflavone ME-344 through suppression of OXPHOS and/or purine biosynthesis in vitro

Venetoclax (VEN), in combination with low dose cytarabine (AraC) or a hypomethylating agent, is FDA approved to treat acute myeloid leukemia (AML) in patients who are over the age of 75 or cannot tolerate standard chemotherapy. Despite high response rates to these therapies, most patients succumb to the disease due to relapse and/or drug resistance, providing an unmet clinical need for novel therapies to improve AML patient survival. ME-344 is a potent isoflavone with demonstrated inhibitory activity toward oxidative phosphorylation (OXPHOS) and clinical activity in solid tumors. Given that OXPHOS inhibition enhances VEN antileukemic activity against AML, we hypothesized that ME-344 could enhance the anti-AML activity of VEN. Here we report that ME-344 enhanced VEN to target AML cell lines and primary patient samples while sparing normal hematopoietic cells. Cooperative suppression of OXPHOS was detected in a subset of AML cell lines and primary patient samples. Metabolomics analysis revealed a significant reduction of purine biosynthesis metabolites by ME-344. Further, lometrexol, a purine biosynthesis inhibitor, synergistically enhanced VEN-induced apoptosis in AML cell lines. Interestingly, AML cells with acquired AraC resistance showed significantly increased purine biosynthesis metabolites and sensitivities to ME-344. Furthermore, synergy between ME-344 and VEN was preserved in these AraC-resistant AML cells. In vivo studies revealed significantly prolonged survival upon combination therapy of ME-344 and VEN in NSGS mice bearing parental or AraC-resistant MV4-11 leukemia compared to the vehicle control. This study demonstrates that ME-344 enhances VEN antileukemic activity against preclinical models of AML by suppressing OXPHOS and/or purine biosynthesis.

Enhancing anti-AML activity of venetoclax by isoflavone ME-344 through suppression of OXPHOS and/or purine biosynthesis

Venetoclax (VEN), in combination with low dose cytarabine (AraC) or a hypomethylating agent, is FDA approved to treat acute myeloid leukemia (AML) in patients who are over the age of 75 or cannot tolerate standard chemotherapy. Despite high response rates to these combination therapies, most patients succumb to the disease due to relapse and/or drug resistance, providing an unmet clinical need for novel therapies to improve AML patient survival. ME-344 is a potent isoflavone with demonstrated inhibitory activity toward oxidative phosphorylation (OXPHOS) and clinical activity in solid tumors. Given that OXPHOS inhibition enhances VEN antileukemic activity against AML, we hypothesized that ME-344 could enhance the anti-AML activity of VEN. Here we report that ME-344 synergized with VEN to target AML cell lines and primary patient samples while sparing normal hematopoietic cells. Cooperative suppression of OXPHOS was detected in a subset of AML cell lines and primary patient samples. Metabolomics analysis revealed a significant reduction of purine biosynthesis metabolites by ME-344. Further, lometrexol, an inhibitor of purine biosynthesis, synergistically enhanced VEN-induced apoptosis in AML cell lines. Interestingly, AML cells with acquired resistance to AraC showed significantly increased purine biosynthesis metabolites and sensitivities to ME-344. Furthermore, synergy between ME-344 and VEN was preserved in these AraC-resistant AML cells. These results translated into significantly prolonged survival upon combination of ME-344 and VEN in NSGS mice bearing parental or AraC-resistant MV4-11 leukemia. This study demonstrates that ME-344 enhances VEN antileukemic activity against preclinical models of AML by suppressing OXPHOS and/or purine biosynthesis.

Abstract 3088: The efficient utilization of paracrine support from established cell lines for breast/ovarian cancer model generation

Ex vivo cancer cell models provide the starting material for in-depth mechanistic studies of cancer. However, the clinical/histopathologic, biomarker, and genetic heterogeneity of breast cancer has not been well represented in the current breast cancer cell model collection. While published breast cancer model generation protocols have been helpful, their high failure rates indicate the urgent need to improve model derivation efficiency. Here, the Broad Cancer Cell Line Factory (CCLF) project presents a novel model derivation technology to generate breast and ovarian cancer organoids with a high success rate by leveraging the paracrine support from historical cancer cell lines.

We observed that most established breast cancer cell lines can grow in a simple basal media with 10% fetal bovine serum; We hypothesized that historical cell lines may secrete vital growth factors that support breast cancer cells' survival and growth. To test this, we randomly selected a pool of 20 breast cancer cell lines, collected its conditioned media (CM20) and incorporated the CM20 as a supplement into our empirical rich media matrix (HYBRID, 16 mixed media conditions) with a Matrigel culturing system. Three-dimensional (3D) structures formed at Day 14-21 in the CM20 supplementary conditions compared to conditions without CM20 and only organoids with the CM20 supplement could be propagated to passage 5 and beyond. We performed pan-cancer targeted sequencing to evaluate tumor content of these organoids at passage 5 with paired tumor tissues. In our first 10 attempts, 95% of organoid cultures were genomically verified as high purity tumor models, indicating the CM20 is essential to enrich breast cancer cell growth in an in vitro culturing setting.

We applied the CM20 to ovarian cancers and observed a similar success rate suggesting a tissue-specific supporting manner. We tested conditioned media collected from other historical cancer cell lines but the breast/ovarian cancer organoid growth effect was not recapitulated. Importantly, when testing the individual breast cancer cell lines from the pool of 20, we discovered one cell line to be supporting the effect. More biochemistry work is needed to dissect the possible factors secreted by the line and molecular mechanisms of cancer cell survivors but preliminary data suggests the secretion factors are most likely proteins.

We generated 27 breast/ovarian cancer cell models using this technology and RNAseq data shows the breast cancer organoids still express their expected molecular subtype markers. 22 breast/ovarian cancer organoids have been propagated long-term with 17(out of 22) deposited to ATCC. Overall, this method provides an efficient model generation rate for female cancers. We anticipate that this method will not only allow us to quickly increase breast cancer cell model diversity but shed light on a new direction for breast cancer dependencies

Citation Format: Rebecca Deasy, Xin Jin, Pierre Michel Jean Beltran, Adel Atari, Madison Liistro, Cheryl Thompson, Stefanie Avril, Julie Boerner, Payal Pradhan, Samuel Klempner, Keith Ligon, William Sellers, Steven Carr, Todd Golub, Yuen-Yi (Moony) Tseng. The efficient utilization of paracrine support from established cell lines for breast/ovarian cancer model generation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3088.

Alcohol dehydrogenase expression patterns in normal prostate, benign prostatic hyperplasia, and prostatic adenocarcinoma in African American and Caucasian men

BACKGROUND

In situ metabolism of ethanol by alcohol dehydrogenases (ADHs) contributes to oxidative damage of cells and DNA and has been linked to carcinogenesis in numerous epithelial tissues. The goal of this study was to determine expression patterns of ADH1 and ADH7 isozymes in normal, hyperplastic (benign prostatic hyperplasia [BPH]) and neoplastic (prostate cancer [PCa]) prostate. Furthermore, racial differences in ADH expression between African Americans and Caucasians were investigated.

METHODS

ADH expression patterns were characterized by density analysis of ADH immunohistochemistry (n = 21) and real-time RT-PCR of total RNAs by laser-capture microdissection (n = 10) and whole tissue formalin-fixed paraffin embedded prostate biopsies (n = 63).

RESULTS

ADH protein is found in normal prostate and is primarily associated with glandular epithelium. Transcripts of ADH1B are suppressed in PCa compared to BPH (p = 0.0095). Racial differences in ADH7 transcripts exist between African American and Caucasian men. A total of 57.6% of biopsies from African American prostates have detectable ADH7 messenger RNA (mRNA) transcripts compared to the 13.3% of Caucasian prostate biopsies with detectable transcripts (p = 0.0005). This increased frequency of detection contributes to higher mean ADH7 mRNA transcript levels in African Americans (p = 0.001).

CONCLUSIONS

To our knowledge this study is the first to report downregulation of ADH1B in neoplastic prostate at the transcriptional level, suggesting protective regulatory functions. ADH7 transcripts were not detectable in all samples and was found in higher frequency and amount in our African American samples. Racial differences in ADH7 within the prostate is a novel finding and should be investigated further.

ONC201 induces the unfolded protein response (UPR) in high- and low-grade ovarian carcinoma cell lines and leads to cell death regardless of platinum sensitivity

Objectives

Treatment of both platinum resistant high grade (HG) and low‐grade (LG) ovarian cancer (OVCA) poses significant challenges as neither respond well to conventional chemotherapy leading to morbidity and mortality. Identification of novel agents that can overcome chemoresistance is therefore critical. Previously, we have demonstrated that OVCA has basal upregulated unfolded protein response (UPR) and that targeting cellular processes leading to further and persistent upregulation of UPR leads to cell death. ONC201 is an orally bioavailable Dopamine Receptor D2 inhibitor demonstrating anticancer activity and was found to induce UPR. Given its unique properties, we hypothesized that ONC201 would overcome platinum resistance in OVCA.

Methods

Cisplatin sensitive and resistant HG OVCA and two primary LG OVCA cell lines were studied. Cell viability was determined using MTT assay. Cell migration was studied using wound healing assay. Apoptosis and mitochondrial membrane potential were investigated using flow cytometry. Analysis of pathway inhibition was performed by Western Blot. mRNA expression of UPR related genes were measured by qPCR. In vivo studies were completed utilizing axillary xenograft models. Co‐testing with conventional chemotherapy was performed to study synergy.

Results

ONC201 significantly inhibited cell viability and migration in a dose dependent manner with IC50’s from 1‐20 µM for both cisplatin sensitive and resistant HG and LG‐OVCA cell lines. ONC201 lead to upregulation of the pro‐apoptotic arm of the UPR, specifically ATF‐4/CHOP/ATF3 and increased the intrinsic apoptosispathway. The compensatory, pro‐survival PI3K/AKT/mTOR pathway was downregulated. In vivo, weekly dosing of single agent ONC201 decreased xenograft tumor size by ~50% compared to vehicle. ONC201 also demonstrated significant synergy with paclitaxel in a highly platinum resistant OVCA cell‐line (OV433).

Conclusions

Our findings demonstrate that ONC201 can effectively overcome chemoresistance in OVCA cells by blocking pro‐survival pathways and inducing the apoptotic arm of the UPR. This is a promising, orallybioavailable therapeutic agent to consider in clinical trials for patients with both HG and LG OVCA.

Abstract 4175: Spectrum of heritable mutations in 43 known and candidate breast cancer susceptibility genes in African American women with breast cancer

Mutations in twenty genes have been associated with heritable breast cancer (BCA), yet the prevalence and clinical implications of most of these genes have not been well described in African American women (AAW). AAW who harbor inherited mutations in BCA susceptibility (BCS) genes are less likely to be identified and thus less likely to receive standard of surgical and preventive care for heritable BCA. A better understanding of heritable mutations in AAW with BCA would ultimately help to define guidelines for clinical management of high risk AAW. We performed targeted sequencing for 288 AAW diagnosed with invasive BCA unselected for family history, age, or BCA subtype. Participants were enrolled in the Detroit Research on Cancer Survivors (ROCS) cohort study or the Karmanos Cancer Institute Biobank. A custom sequencing panel captured the coding sequence of 43 genes (Known: ATM, BARD1, BRCA1, BRCA2, BRIP1, CDH1, CHEK2, MRE11A, MSH6, MUTYH, NBN, NF1, PALB2, PMS2, PTEN, RAD50, RAD51C, RAD51D, STK11, TP53; Candidate: MLH1, MSH2, PMS1, SEC23B, BLM, ATR, BAP1, BBC3, CDKN1A, FAM175A, FANCA, FANCC, FANCI, FANCL, FANCM, GEN1, RAD51B, RBBP8, RECQL, RINT1, TP53BP1, XRCC1, XRCC3). Samples were sequenced using the Illumina MiSeq platform multiplexed for 100X mean depth of coverage. Intronic or synonymous exonic variants and those with <40 reads, or alternative allele frequency >3% in African populations in the 1000 Genomes, ExAC, or NHLBI ESP6500SI databases were filtered. Only variants in known BCS genes could be considered definitively pathogenic (DP), defined as missense variants categorized as pathogenic in ClinVar and all frameshift, nonsense, and splice site variants. All other variants were defined as variants of uncertain significance (VUS). We identified 54 women harboring DP mutations in 15 known BCS genes. Mutations in BRCA1/2 accounted for 32% of all DP mutations. Notably, nearly 17% of DP mutations were in MSH6, a gene only recently described as associated with increased risk of BCA in the general population. Among women with these DP mutations, nearly 25% had no high-risk characteristics. Ten VUS in known BCS genes were identified, where 4 were reported in ClinVar (BARD1, RAD5C, BRCA2, PMS2) and 6 were novel (PMS2, BRCA1, MUTYH, MSH6, NBN, MRE11). Among the candidate BCS genes, 63 VUS were identified: 51 frameshift variants, 5 nonsense variants, 3 splice site variants, and 4 missense mutations predicted to be pathogenic by ≥8/9 algorithms. Nearly 60% of participants had neither a DP mutation or VUS. These data suggest that AAW with BCA have a unique mutation spectrum and may benefit from BCS gene sequencing regardless of family history, age, or subtype. Additional sequencing in AAW will lay the foundation for identification of germline factors associated with BCA risk and prognosis specifically in AAW and offer opportunities for personalized risk assessment.

Citation Format: Kristen Purrington, Gregory Dyson, Douglas Craig, Julie Boerner, Julie Madden, Jennifer Beebe-Dimmer, Ann G. Schwartz, Michael Simon. Spectrum of heritable mutations in 43 known and candidate breast cancer susceptibility genes in African American women with breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4175.

Biomarkers and Bone Imaging Dynamics Associated with Clinical Outcomes of Oral Cabozantinib Therapy in Metastatic Castrate-Resistant Prostate Cancer

PURPOSE

Cabozantinib is a multitargeted tyrosine kinase inhibitor that demonstrated remarkable responses on bone scan in metastatic prostate cancer. Randomized trials failed to demonstrate statistically significant overall survival (OS). We studied the dynamics of biomarker changes with imaging and biopsies pretherapy and posttherapy to explore factors that are likely to be predictive of efficacy with cabozantinib.Experimental Design: Eligibility included patients with metastatic castrate-resistant prostate cancer with normal organ function and performance status 0-2. Cabozantinib 60 mg orally was administered daily. Pretherapy and 2 weeks post, ^99mTc-labeled bone scans, positron emission tomography with ¹⁸F-sodium fluoride (NaF-PET) and ¹⁸F-(1-(2'-deoxy-2'-fluoro-β-D-arabinofuranosyl) thymine (FMAU PET) scans were conducted. Pretherapy and posttherapy tumor biopsies were conducted, and serum and urine bone markers were measured.

RESULTS

Twenty evaluable patients were treated. Eight patients had a PSA decline, of which 2 had a decline of ≥50%. Median progression-free survival (PFS) and OS were 4.1 and 11.2 months, respectively, and 3 patients were on therapy for 8, 10, and 13 months. The NaF-PET demonstrated a median decline in SUVmax of -56% (range, -85 to -5%, n = 11) and -41% (range, -60 to -25%, n = 9) for patients who were clinically stable and remained on therapy for ≥4 or <4 cycles, respectively. The FMAU PET demonstrated a median decline in SUVmax of -44% (-60 to -14%) and -42% (-63% to -23%) for these groups. The changes in bone markers and mesenchymal epithelial transition/MET testing did not correlate with clinical benefit.

CONCLUSIONS

Early changes in imaging and tissue or serum/urine biomarkers did not demonstrate utility in predicting clinical benefit with cabozantinib therapy.

Phase II Study of Maintenance Pembrolizumab in Patients with Extensive-Stage Small Cell Lung Cancer (SCLC)

OBJECTIVE

The aim of this study was to assess the efficacy of maintenance pembrolizumab in patients with extensive-stage SCLC after treatment with platinum and etoposide.

METHODS

Patients with extensive-stage SCLC with a response or stable disease after induction chemotherapy were eligible. Pembrolizumab at a dose of 200 mg administered intravenously every 3 weeks was initiated within 8 weeks of the last cycle of chemotherapy. The primary end point of the study was progression-free survival (PFS) from study registration, with overall survival (OS) as a key secondary end point. Available tumor tissue was assessed for expression of programmed death ligand 1 (PD-L1) both in the tumor cells and in the surrounding stroma. Blood for circulating tumor cells was collected before the first, second, and third cycles of pembrolizumab.

RESULTS

Of the 45 patients enrolled, 56% were male and 22% had treated brain metastases. The median PFS was 1.4 months (95% confidence interval [CI]: 1.3-2.8), with a 1-year PFS of 13%. The median OS was 9.6 months (95% CI: 7.0-12), with a 1-year OS of 37%. Of the 30 tumors that could be assessed, three had PD-L1 expression (≥1%) in the tumor cells. A total of 20 tumors could be assessed for PD-L1 expression in the stroma. The median PFS in the eight patients with tumors positive for expression of PD-L1 at the stromal interface was 6.5 months (95% CI: 1.1-12.8) compared with 1.3 months (95% CI: 0.6-2.5) in 12 patients with tumors negative for this marker. No unexpected toxicities were observed.

CONCLUSION

Maintenance pembrolizumab did not appear to improve median PFS compared with the historical data. However, the 1-year PFS rate of 13% and OS rate of 37% suggest that a subset of patients did benefit from pembrolizumab.

Phase 0 Trial of AZD1775 in First-Recurrence Glioblastoma Patients

Purpose: AZD1775 is a first-in-class Wee1 inhibitor with dual function as a DNA damage sensitizer and cytotoxic agent. A phase I study of AZD1775 for solid tumors suggested activity against brain tumors, but a preclinical study indicated minimal blood-brain barrier penetration in mice. To resolve this controversy, we examined the pharmacokinetics and pharmacodynamics of AZD1775 in patients with first-recurrence, glioblastoma.Patients and Methods: Twenty adult patients received a single dose of AZD1775 prior to tumor resection and enrolled in either a dose-escalation arm or a time-escalation arm. Sparse pharmacokinetic blood samples were collected, and contrast-enhancing tumor samples were collected intraoperatively. AZD1775 total and unbound concentrations were determined by a validated LC/MS-MS method. Population pharmacokinetic analysis was performed to characterize AZD1775 plasma pharmacokinetic profiles. Pharmacodynamic endpoints were compared to matched archival tissue.Results: The AZD1775 plasma concentration-time profile following a single oral dose in patients with glioblastoma was well-described by a one-compartment model. Glomerular filtration rate was identified as a significant covariate on AZD1775 apparent clearance. AZD1775 showed good brain tumor penetration, with a median unbound tumor-to-plasma concentration ratio of 3.2, and achieved potential pharmacologically active tumor concentrations. Wee1 pathway suppression was inferred by abrogation of G₂ arrest, intensified double-strand DNA breakage, and programmed cell death. No drug-related adverse events were associated with this study.Conclusions: In contrast to recent preclinical data, our phase 0 study of AZD 1775 in recurrent glioblastoma indicates good human brain tumor penetration, provides the first evidence of clinical biological activity in human glioblastoma, and confirms the utility of phase 0 trials as part of an accelerated paradigm for drug development in patients with glioma. Clin Cancer Res; 24(16); 3820-8. ©2018 AACRSee related commentary by Vogelbaum, p. 3790.

Heterogeneity of Human Breast Stem and Progenitor Cells as Revealed by Transcriptional Profiling

During development, the mammary gland undergoes extensive remodeling driven by stem cells. Breast cancers are also hierarchically organized and driven by cancer stem cells characterized by CD44⁺CD24^low/− or aldehyde dehydrogenase (ALDH) expression. These markers identify mesenchymal and epithelial populations both capable of tumor initiation. Less is known about these populations in non-cancerous mammary glands. From RNA sequencing, ALDH⁺ and ALDH⁻CD44⁺CD24⁻ human mammary cells have epithelial-like and mesenchymal-like characteristics, respectively, with some co-expressing ALDH⁺ and CD44⁺CD24⁻ by flow cytometry. At the single-cell level, these cells have the greatest mammosphere-forming capacity and express high levels of stemness and epithelial-to-mesenchymal transition-associated genes including ID1, SOX2, TWIST1, and ZEB2. We further identify single ALDH⁺ cells with a hybrid epithelial/mesenchymal phenotype that express genes associated with aggressive triple-negative breast cancers. These results highlight single-cell analyses to characterize tissue heterogeneity, even in marker-enriched populations, and identify genes and pathways that define this heterogeneity.

•

Isolation and RNA-seq of ALDH⁺ and CD44⁺CD24⁻ breast cells

•

Unlike in cancer, there is substantial overlap in ALDH⁺ and CD44⁺CD24⁻ populations

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Single-cell analysis of ALDH⁺ cells identifies unexpected subpopulation structure

•

Hybrid epithelial/mesenchymal ALDH⁺ cells have a cancer-like expression signature

Abstract 1396: Role of epigenetic reader and alternative mRNA splicing variant MBD2 variant 2 in triple-negative breast cancer

Background: Among all breast cancer patients, those diagnosed with the triple-negative breast cancer (TNBC) subtype have the worst prognosis, in part attributable to the fact that TNBC lacks targets for effective molecularly-targeted therapies. The concept that EGFR inhibitor drugs could be used as a targeted treatment against TNBC has been put forth because roughly 50% of TNBC express high levels of EGFR. However clinical trials targeting EGFR did not significantly improve patient outcomes. Our recent work offers a potential explanation as to why EGFR inhibitors failed and supports an innovative therapeutic approach combining an EGFR tyrosine kinase inhibitor with the novel antioxidant biologic, CAT-SKL. Our data indicate that inhibition of cancer stem cell-like cells depends on antioxidant-induced downregulation of an alternative mRNA splice variant of the methyl-CpG binding domain 2 gene, MBD2_v2.

Objective and Methods: The purpose of the present study was to evaluate the importance of MBD2_v2 in TNBC and better understand how CAT-SKL regulates its expression. Using TNBC cell lines we investigated the effects of MBD2_v2 expression on tumor initiation capacity. Furthermore we studied MBD2_v2 mRNA levels in an in vivo tumor xenograph mouse model of TNBC and in human TNBC samples using an existing database. Then by RNA-seq analysis we assessed how CAT-SKL regulates MBD2_v2 expression in TNBC cells through differential gene expression.

Results: The results support that MBD2_v2 expression is regulated by redox signaling in TNBC cells, which is tightly linked to TNBC cell tumor initiation capacity. Furthermore, MBD2_v2 was upregulated in tumors harvested from overweight mice, which also displayed increased tumor take rate, suggesting that a pro-inflammatory tumor microenvironment could play a role in promoting MBD2_v2 expression. In addition, RNA-seq analysis identified an overrepresentation of mRNA splicing factors with expression downregulated by CAT-SKL treatment of TNBC cells. From this gene set two splicing co-factors are highlighted: SRRM1 and CPSF3. These co-factors are critical for splicing factor function, 3’ end formation and polyadenylation; and both have been linked via protein-protein interaction to a relevant exonic splicing enhancer site in exon 3 of the MBD2 _v2 transcript. Finally, according to the Kaplan Meier Plotter database high MBD2_v2 levels in BC were associated with shorter relapse free survival.

Conclusion: Our investigation sheds light on the relevance of MBD2_v2 expression in TNBC, and how a select antioxidant regulates its expression. The application of which holds promise of a novel, targeted therapeutic modality for TNBC, the subtype with the worst prognosis and highest need for treatment options.

Citation Format: Emily A. Girsch, Bin Bao, Cristina Mitrea, Gregory Dyson, Julie Boerner, Lisa Polin, Stan R. Terlecky, Aliccia Bollig-Fischer. Role of epigenetic reader and alternative mRNA splicing variant MBD2 variant 2 in triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1396. doi:10.1158/1538-7445.AM2017-1396

Phase II study of maintenance pembrolizumab (pembro) in extensive stage small cell lung cancer (ES-SCLC) patients (pts)

8504

Background: The median progression free survival (PFS) and overall survival (OS) following initial chemotherapy in ES-SCLC pts are 2 and 7 months, respectively (Ready N, J Clin Oncol 2015). We evaluated the benefits of maintenance pembro in ES-SCLC pts who had response/stable disease after 4-6 cycles of platinum/etoposide. Methods: Pts were required to begin pembro within 8 weeks of completion of chemotherapy, with restaging scans no more than 3 weeks prior to start of pembro. Prophylactic cranial radiation was permitted. Pts were treated with pembro 200 mg I.V. every 3 weeks for a maximum of 2 years. Disease assessment was done every 2 cycles for the first 6 cycles and then as per investigator discretion. Primary end point of the study was PFS. PFS according to immune related response criteria (irPFS) and OS were also assessed. Tumor tissue was analyzed for PD-L1 expression by the DAKO 22C3 antibody. Any level of expression was considered as positive for PDL1. Blood for circulating tumor cells (CTCs) was collected prior to first, second and third cycle of pembro. Results: Of the 45 pts enrolled, 55% were males and 22% had brain metastases. Median age was 66 years. The median time from end of chemotherapy to start of pembro was 5 weeks. Median number of pembro cycles was 4 (1-20 cycles). 35 pts had measurable disease at study entry. The disease control rate with pembro was 42% (1 CR, 3 PR, 15 SD). At a median follow up of 6 months, the median PFS was 1.4 months (90% CI-1.3-4.0) and the irPFS was 4.7 months (90% CI- 1.8-6.7). The median OS was 9.2 months (90% CI-6.1-15.2). 11 pts are still on therapy (3-20 cycles). The median CTC prior to pembro was 1 (0-256, n=37 pts). Each unit increase in baseline CTC correlated with worse PFS (p = 0.052; adjusted for brain mets, age and sex). PDL1 could be assessed in 35 pts and was positive in 1 pt. Most common adverse events were fatigue, nausea, cough and dyspnea. One pt developed atrio-ventricular conduction block and 1 pt type 1 diabetes. Conclusions: Maintenance pembro did not improve PFS in these patients but favorable OS suggests that some SCLC patients can benefit from maintenance pembro. Biomarkers to identify patients most likely to benefit from pembro need to be defined. Clinical trial information: NCT02359019.

Abstract A15: Breast cancer subtype subsequent to a benign breast biopsy among African American women

Introduction: Most clinical models to estimate risk of invasive breast cancer include history of benign breast disease (BBD) as a covariate, as these women represent a higher risk group compared to the general population. A better understanding of the association between BBD and breast cancer is necessary to improve the utility of these risk models, particularly with respect to tumor subtype. This may be especially important for African American women who are more likely to present with aggressive cancers compared to white women. Here we present tumor subtypes from a higher risk cohort of African American women with a history of BBD.

Methods: Benign breast biopsies from 3,865 African American women with BBD diagnosed from 1997-2010 were examined for 14 benign features, and followed for subsequent breast cancers in metropolitan Detroit, Michigan using medical records and data from the Detroit Surveillance, Epidemiology and End Results (SEER) program. Immunohistochemistry analysis was performed for the following 6 markers: estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), Ki-67, epidermal growth factor receptor (EGFR) and cytokeratin 5/6 (CK 5/6) in order to categorize the subsequent breast cancers by subtype. Briefly, ER and PR were utilized to classify tumors as luminal or non-luminal, and then further classification was made based HER2. Luminal tumors were also classified by Ki-67 expression, and triple negative tumors (ER/PR/HER2 negative) were further classified based on expression of either CK5/6 or EGFR, resulting in 6 categories.

Results: 210 women (5.4% of the total cohort) with a subsequent breast cancer were identified over a median follow-up time of 12.3 years (range: 0.6 - 18.0). Analysis of all 6 markers is complete for half of the tumors (104). The majority of the subsequent cancers were invasive (n=72, 69.2%). Most of the invasive tumors were luminal B, HER2- (37.5%), followed by luminal A (31.9%), triple negative (19.4%), non-luminal, HER2+ (6.9%) and luminal B, HER2+ (4.2%). Of the 14 triple negative cancers (19.4%), 8 were negative for CK5/6 and EGFR (5 negative phenotype, 57.1%) and 6 were core basal (42.9%). Among the 32 in situ tumors, the majority were luminal A (n=26, 81.3%), followed by luminal B, HER2- (n=5, 15.6%) and there was a single tumor classified as 5 negative. Compared to population-based SEER data from 5,268 African American women with invasive breast cancer and available data on 3 markers (ER, PR, and HER2) diagnosed in 2010, our cohort is similar with respect to tumor subtype.

Conclusions: The women with a previous benign breast biopsy in our cohort who develop a subsequent breast cancer have subtypes that are similar to the general African American population in the United States. Thus, our BBD cohort represents the full spectrum of invasive breast cancers with respect to subtype, including triple negative tumors.

Citation Format: Julie J. Ruterbusch, Michele L. Cote, Julie Boerner, Eman Abdulfatah, Baraa Alosh, Vishakha Pardeshi, MHD Fayez Daaboul, Woodlyne Roquiz, Rouba Ali-Fehmi, Sudeshna Bandyopadhyay. Breast cancer subtype subsequent to a benign breast biopsy among African American women. [abstract]. In: Proceedings of the AACR Special Conference: Improving Cancer Risk Prediction for Prevention and Early Detection; Nov 16-19, 2016; Orlando, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(5 Suppl):Abstract nr A15.

Abstract B33: Determination of protein expression of candidate prostate cancer genes from a novel region on chromosome 7 identified in African American men

In the United States, African American (AA) men are at 60% higher risk of developing prostate cancer than European American (EA) men, and AA men are 2.4 times more likely to die from prostate cancer than EA men. Although these disparities are frequently attributed to the greater aggressiveness of prostate cancer among AA men, it is not known what causes that prostate cancer aggressiveness in AA men. To identify germline genetic variation that could explain some of this disparity, our previous admixture mapping study identified a novel region on chromosome 7q31-34 where local ancestry was associated with risk of disease. The main objective of this study is to investigate whether candidate genes in this gene region show differences in protein product expression by cell line origin (AA vs. EA) and by cell line metastatic potential. We specifically examined the expression of three proteins sourced from this gene region through immunoblot analysis, filamin C (FLNC), glutamate receptor metabotropic B (GRM8), and cadherin-like and PC-esterase domain containing 1 (CPED1). The cell lines DU-145, PC3, LNCaP, RWPE1, and WPE1 were derived from biological specimens from EA men, whereas the PCa2b and the RC77T cell lines were sourced from AA men. The RWPE1 and WPE1 cell lines were derived from normal prostate cells, while the remaining cell lines were derived from metastatic prostate cancers. Using immunoblot analysis, we found that GRM8 is expressed at higher levels in the cell lines derived from AA men with prostate cancer compared to those from EA men with prostate cancer. In contrast, FLNC and CPED1 are expressed at higher levels in the cell lines from EA men with prostate cancer compared to those from AA men with prostate cancer. Interestingly, both FLNC and CPED1 expression is also low in the androgen sensitive LNCaP cell line. Importantly, these results are consistent with our fine mapping results in AA men, where the SNP with greatest evidence for association is located. Further, previous studies have demonstrated that the methylation status and mRNA expression of CPED1 and FLNC differed between prostate cancers from AA and EA men. Taken together, these results provide us with a foundation to test the relevance of these genes in prostate cancer growth and metastasis and contribute to our understanding of the molecular differences in prostate cancer between EA and AA men.

Citation Format: Casey Wizner, Julie Ruterbusch, Nicole Kubinec, Gregory Dyson, Albert Levin, Julie Boerner, Cathryn Bock. Determination of protein expression of candidate prostate cancer genes from a novel region on chromosome 7 identified in African American men. [abstract]. In: Proceedings of the Ninth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2016 Sep 25-28; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(2 Suppl):Abstract nr B33.

Epidermal Growth Factor Receptor Kinase Inhibitors Synergize with TCDD to Induce CYP1A1/1A2 in Human Breast Epithelial MCF10A Cells

CYP1A1 and CYP1A2 are transcriptionally activated in the human normal breast epithelial cell line MCF10A following exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Shifting MCF10A cultures to medium deficient in serum and epidermal growth factor (EGF) caused rapid reductions in the activated (i.e., phosphorylated) forms of extracellular regulated kinases (ERKs) and the epidermal growth factor receptor (EGFR). Shifting to serum/EGF-deficient medium also enhanced TCDD-mediated induction of cytochrome P450 (CYP)1A1 Treatment of cells cultured in complete medium with the EGFR inhibitors gefitinib (Iressa), AG1478, and CI-1033 resulted in concentration-dependent reductions of active EGFR and ERKs, and increased CYP1A1 mRNA content ∼3- to 18-fold above basal level. EGFR inhibitors synergized with TCDD and resulted in transient CYP1A1 and CYP1A2 mRNA accumulations ∼8-fold greater (maximum at 5 hours) than that achieved with only TCDD. AG1478, gefitinib, and TCDD individually induced small increases (∼1.2- to 2.5-fold) in CYP1A1 protein content but did not cause additive or synergistic accumulations of CYP1A1 protein when used in combination. The mitogen-activated protein kinase kinase inhibitor PD184352 inhibited ERK and EGFR activation in a concentration-dependent fashion without causing CYP1A1 mRNA accumulation. However, cotreatment with PD184352 potentiated TCDD-mediated CYP1A1 induction. TCDD-mediated induction of CYP1A1 in MCF7-TET on-EGFR cells, a MCF7 variant in which EGFR expression can be controlled, was not affected by the activity status of EGFR or ERKs. Hence, EGFR signaling mutes both basal and ligand-induced expression of two aryl hydrocarbon receptor-responsive P450s in MCF10A cultures. However, these effects are cell context-dependent. Furthermore, CYP1A1 mRNA and protein abundance are not closely coupled in MCF10A cultures.

Targeting matriptase in breast cancer abrogates tumour progression via impairment of stromal-epithelial growth factor signalling

Matriptase is an epithelia-specific membrane-anchored serine protease that has received considerable attention in recent years due to its consistent dysregulation in human epithelial tumors, including breast cancer. Mice with reduced levels of matriptase display a significant delay in oncogene-induced mammary tumor formation and blunted tumor growth. The abated tumor growth is associated with a decrease in cancer cell proliferation. Here we demonstrate by genetic deletion and silencing that the proliferation impairment in matriptase deficient breast cancer cells is caused by their inability to initiate activation of the c-Met signaling pathway in response to fibroblast-secreted pro-HGF. Similarly, inhibition of matriptase catalytic activity using a selective small-molecule inhibitor abrogates the activation of c-Met, Gab1 and AKT, in response to pro-HGF, which functionally leads to attenuated proliferation in breast carcinoma cells. We conclude that matriptase is critically involved in breast cancer progression and represents a potential therapeutic target in breast cancer.

Regulation of the Src-PP2A interaction in tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-induced apoptosis

TNF-related apoptosis-inducing ligand (TRAIL) selectively induces apoptosis in transformed and tumor cells but not in normal cells, making it a promising agent for cancer therapy. However, many cancer cells are resistant to TRAIL, and the underlying mechanisms are not fully understood. Here, we show that the regulation of the PP2A and Src interaction plays a critical role in TRAIL resistance. Specifically, we show that TRAIL treatment activates the tyrosine kinase Src, which subsequently phosphorylates caspase-8 at tyrosine 380, leading to the inhibition of caspase-8 activation. We also show that upon TRAIL treatment, Src, caspase-8, and PP2A/C (a catalytic subunit of the PP2A phosphatase) are redistributed into lipid rafts, a microdomain of the plasma membrane enriched with cholesterol, where PP2A dephosphorylates Src at tyrosine 418 and in turn inhibits caspase-8 phosphorylation. Furthermore, we find that TRAIL treatment causes PP2A/C degradation. These data suggest that the balance between Src-mediated caspase-8 phosphorylation and the inactivation of Src-mediated caspase-8 phosphorylation by PP2A determines the outcome of TRAIL treatment in breast cancer cells. Therefore, this work identifies a novel mechanism by which the interaction between PP2A and Src in the context of caspase-8 activation modulates TRAIL sensitivity in cancer cells.

Abstract 1026: Combating resistance to EGFR inhibitors: eIF4B as a novel target

Triple negative breast cancer (TNBC) patients suffer from a highly malignant and aggressive cancer that currently has no efficacious therapy. These patients have a high rate of relapse and often develop resistance to chemotherapy. Many TNBCs, both in vitro and in vivo, have elevated levels of epidermal growth factor receptor (EGFR) but are resistant to EGFR inhibitors as a monotherapy. The TNBC cell line, BT20, has increased levels of EGFR and is resistant to EGFR inhibitors. To identify the signaling pathways that remain phosphorylated after treatment with gefitinib, an EGFR tyrosine kinase inhibitor (TKI), we used mass spectrometry based phospho-proteomics. Through these assays we identified many components of the mTOR pathway phosphorylated in the presence of gefitinib and further sought to explore this pathway as a mechanism of resistance to EGFR inhibitors in TNBC. mTOR inhibitors have been investigated in the clinic due to their ability to inhibit the PI3Kinase/Akt pathway thus decreasing cell survival and proliferation. Inhibiting mTOR also importantly inhibits translation. Despite activation of these pathways our TNBC cell lines, BT20, MDA-MB-123, and MDA-MB-468 are resistant to temsirolimus, an mTOR inhibitor. Our studies have found that dual treatment with an mTOR inhibitor and an EGFR TKI has a synergistic effect on decreasing TNBC cell viability, but the mechanism of this synergy is not understood. We have found that the abrogation of both EGFR and mTOR signaling does not alter the phosphorylation status of key signaling pathways including MAPK and Akt. Instead, our preliminary data have identified the translational control protein eIF4B as potentially key fragile point in EGFR and mTOR inhibitor synergy. Therefore, in this study we hypothesized that mTOR inhibition will sensitize TNBC cells to EGFR TKIs through the inhibition of eIF4B phosphorylation. Small molecules have yet to be identified to abrogate the function of eIF4B, which when phosphorylated enhances the helicase activity of eIF4A critical to translation. Therefore, we knockdown eIF4B expression and found a decrease in cell survival comparable to the decrease observed with gefitinib and temsirolimus treatment. In addition, we have identified p70S6K and p90RSK as kinases directly responsible for eIF4B phosphorylation, such that both molecules need to be inactivated in order for eIF4B phosphorylation to be inhibited. This inactivation correlates with a loss of cell growth and viability and a decrease in clonogenic cell survival. Lastly, we have shown that the downstream functions of eIF4B phosphorylation are abrogated with EGFR and mTOR inhibitors. Therefore, taken together these data suggest that in the presence of activated MAPK and AKT, EGFR and mTOR inhibitors have the ability to abrogate cell growth, viability, and survival via disruption of the translational control mechanisms through eIF4B.

Citation Format: Julie Madden, Kelly Mueller, Aliccia Bollig-Fischer, Paul Stemmer, Julie Boerner. Combating resistance to EGFR inhibitors: eIF4B as a novel target. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1026. doi:10.1158/1538-7445.AM2013-1026

Abstract 1068: Inhibition of the phosphorylation of eIF4 molecules sensitizes EGFR expressing breast cancers to EGFR inhibitors

Triple-negative breast cancers have a poor prognosis and lack an effective targeted therapeutic. Even though ∼50% of triple-negative breast cancers express epidermal growth factor receptor (EGFR), they are resistant to EGFR tyrosine kinase inhibitors (TKI). Although the activation of several tyrosine kinases including Met, c-Src, and IGF-IR have been found to correlate with EGFR TKI resistance, the mechanism of this de novo resistance is still being elucidated. The BT20 breast cancer cell line has amplified EGFR expression yet is resistant to EGFR TKIs. Phospho-proteomic analysis by mass spectrometry was used to identify proteins that remain phosphorylated after gefitinib treatment. These proteins included Raptor, PDK1, and GSK3, implicating the Akt and mTOR pathways in EGFR TKI resistance. Despite activation of these pathways, BT20 cells were resistance to the mTOR antagonist temsirolimus. However, temsirolimus was able to sensitize BT20 cells to gefitinib which led to a synergistic decrease in cell survival. Similar results have been observed by others using different inhibitors; however, the mechanism of this synergistic decrease in cell survival has not been identified. These data suggest that EGFR and mTOR activation regulate cell survival through parallel signaling pathways and that both pathways need to be inhibited to abrogate growth and survival. This is supported by the observation that the PI3Kinase/Akt signaling pathway was unaffected by gefitinib or temsirolimus treatment alone. In addition, the combination of EGFR and mTOR inhibitors had no effect on PI3Kinase/Akt or Ras/MAPK signaling, despite the synergistic decrease in cell survival. However, further immunoblotting showed a pronounced inhibition in activation of the eIF4 family in the mTOR translational control pathway with dual treatment of gefitinib and temsirolimus, an abrogation not significantly observed with either treatment alone. These results suggest that inhibiting mTOR signaling alone is insufficient to modulate the translational control pathway in BT20 cells and that EGFR signals independent of mTOR to activate this pathway. These data demonstrate that phosphorylation and subsequent regulation of these translational control molecules may be critical to the survival of BT20 cells. Indeed, the combination of gefitinib and temsirolimus stimulated apoptosis in BT20 cells, supporting the idea that inhibiting the mTOR pathway will sensitize breast cancers expressing EGFR to gefitinib inhibition. In summary, these data provide strong evidence for the presence of a de novo EGFR TKI resistance pathway in breast cancers that occurs through the activation of the mTOR pathway and therapy for EGFR positive breast cancers could be improved with dual treatment of EGFR TKI and an mTOR antagonist.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1068. doi:1538-7445.AM2012-1068

Strong expression association between matriptase and its substrate prostasin in breast cancer

Breast cancer tumorigenesis is accompanied by increased levels of extracellular proteases that are capable of remodeling the extracellular matrix as well as cleaving and activating growth factors and signaling receptors that are critically involved in neoplastic progression. Multiple studies implicate the membrane anchored serine protease matriptase (also known as MT-SP1 and epithin) in breast cancer. The pro-form of the GPI-anchored serine protease prostasin has recently been identified as a physiological substrate of matriptase and the two proteases are co-expressed in multiple healthy tissues. In this study, the inter-relationship between the two membrane-anchored serine proteases in breast cancer was investigated using breast cancer cell lines and breast cancer patient samples to delineate the association between matriptase and prostasin. We used Western blotting to determine the expression of matriptase and prostasin proteins in a panel of breast cancer cell lines and immunohistochemistry to assess the expression in serial sections from breast cancer tissue arrays. We demonstrate that the expression of matriptase and prostasin is closely correlated in breast cancer cell lines as well as in breast cancer tissue samples. Furthermore, matriptase and prostasin display a near identical spatial expression pattern in the epithelial compartment of breast cancer tissue. These data suggest that the matriptase-prostasin cascade might play a critical role in breast cancer.

PD08-08: Preclinical Efficacy of the Combination of Met and Src Family Kinase Inhibitors in Triple-Negative Breast Cancer

Background: Epidermal growth factor receptor (EGFR), although overexpressed in almost 60% of all triple-negative breast cancers, has yet to be identified as an effective therapeutic target for the treatment of the disease. We have previously shown in cell culture models of triple-negative breast cancer that primary resistance to EGFR tyrosine kinase inhibitors through ligand-independent phosphorylation can be overcome by co-inhibiting EGFR with either Met or Src family kinases (SFKs). We also demonstrated that inhibiting Met kinase activity reduced EGFR and c-Src phosphorylation and inhibiting SFK reduced EGFR phosphorylation. Taken together, these data suggest that EGFR, Met and SFKs regulate the activity of each other through transphosphorylation. This process of transphosphorylation, or crosstalk, allows for the continued activation of key signaling proteins required for proliferation and transformation. Here we demonstrate that inhibiting both Met and SFKs decreases cell viability and eliminates the need for inhibition of EGFR tyrosine kinase activity, as the autophosphorylation sites of EGFR were lost with the combination treatment.

Methods: Seven triple-negative (SUM102, SUM149, SUM229, SUM1315, BT20, BT549, MDA-MB-231), two HER2+ (SUM190 and SKBr3), and two ER/PR+ (MCF7 and T47D) breast cancer cell lines were used to test the efficacy of the combination of Met and SFK inhibitors, Arq-197 and dasatinib, respectively. Cell viability after drug treatment was assessed by MTT assays. IC50 values were calculated and drug synergy calculations were performed. Transphosphorylation was measured by immunoblotting using phospho-specific antibodies. Apoptosis was characterized by immunoblotting.

Results: All seven triple-negative breast cancer cell lines demonstrated decreased cell viability with the combination of Arq-197 and dasatinib when compared with either drug alone. In contrast, none of the HER2+ or ER/PR+ breast cancer cell lines had any additional loss of viability with the combination treatment. We found that the interactions between Arq-197 and dasatinib were synergistic in several of the breast cancer cell lines. Specifically, in one such cell line (BT20), the combinatorial index values were less than 1.0. Interestingly, in this cell line, the tyrosine phosphorylation levels on residues 1068 and 992 of EGFR were significantly altered with the combination treatment and activation of apoptotic proteins, including PARP, occurred.

Conclusions: These data demonstrate that two tyrosine kinases, known to be downstream of EGFR activation, interact to promote resistance to EGFR inhibitors. However, inhibiting both Met and SFKs was sufficient to decrease cell viability and stimulate apoptosis in triple-negative breast cancer cells. Further studies to validate the relevance of these findings are ongoing.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr PD08-08.

Elevated serum cytokines correlated with altered behavior, serum cortisol rhythm, and dampened 24-hour rest-activity patterns in patients with metastatic colorectal cancer

PURPOSE

Incapacitating symptom burden in cancer patients contributes to poor quality of life (QOL) and can influence treatment outcomes because of poor tolerance to therapy. In this study, the role of circulating cytokines in the production symptoms in cancer patients is evaluated.

EXPERIMENTAL DESIGN

Eighty patients with metastatic colorectal cancer with either normal (group I, n = 40) or dampened (group II, n = 40) 24-hour rest/activity patterns measured by actigraphy were identified. Actigraphy patterns were correlated with QOL indices, serum cortisol obtained at 8:00 a.m. and 4:00 p.m. and with serum levels of transforming growth factor-alpha, tumor necrosis factor-alpha, and interleukin 6 (IL-6) obtained at 8:00 a.m. and analyzed in duplicate by ELISA. Cytokine levels and survival were also correlated.

RESULTS

Group II patients had significantly higher pre treatment levels of all three cytokines, displayed significantly poorer emotional and social functioning, had higher fatigue, more appetite loss, and poorer performance status compared with group I patients. Transforming growth factor-alpha (TGF-alpha) and IL-6 were significantly increased in the patients with WHO performance status >1 and in those with appetite loss. Fatigue was significantly associated with elevated TGF-alpha only. IL-6 was increased in those patients with extensive liver involvement and multiple organ replacement, and it was significantly correlated with dampened cortisol rhythm. In a multivariate analysis, IL-6 was correlated with poor treatment outcome.

CONCLUSIONS

Significant correlations were found between serum levels of TGF-alpha and IL-6, circadian patterns in wrist activity and serum cortisol and tumor-related symptoms in patients with metastatic colorectal cancer. These data support the hypothesis that some cancer patient's symptoms of fatigue, poor QOL, and treatment outcome are related to tumor or host generated cytokines and could reflect cytokine effects on the circadian timing system. This interplay between cytokine signaling pathways, the hypothalamic-pituitary-adrenal axis, the autonomic nervous system, and efferent pathways of the suprachiasmatic nucleus that control circadian physiology, opens the way to new rational interventions for symptom management in cancer patients.

In vitro antimicrobial susceptibility testing of Borrelia burgdorferi: influence of test conditions on minimal inhibitory concentration (MIC) values

A broth microdilution assay was performed to determine the minimal inhibitory concentrations (MICs) of 25 antimicrobial agents for two strains of Borrelia (B.) burgdorferi sensu lato and one strain of B. hermsii. The method comprised BSK II medium lacking gelatin and an incubation period of 72 hours. To investigate the influence of reading mode and density of inoculum on MIC values, microscopical as well as macroscopical MIC reading was performed using standardized final inocula of 10(6) and 10(7) borreliae/ml. Data were processed by two-way analysis of variance. In the microdilution assay, MIC values were significantly influenced either by the inoculum density or reading mode. However, using clearly defined criteria for macroscopical endpoint determination, MICs from macroscopical and microscopical reading were found to be in close agreement. B. burgdorferi sensu lato strains tested were highly susceptible to azithromycin, erythromycin, mezlocillin, piperacillin as well as ceftriaxone, with MICs ranging from < or = 0.016 to 0.125 microgram/ml. B. hermsii was highly susceptible to azithromycin and erythromycin. In comparison to B. hermsii, the beta-lactam antibiotics revealed a significantly higher activity and gentamicin, ofloxacin, and rifampin revealed a significantly lower activity against B. burgdorferi sensu lato strains. To further investigate interactions between BSK II medium, incubation time, and antibiotic efficacy, an agar diffusion bioassay was performed. Out of seven antibiotics tested, the activities of mezlocillin, penicillin G, and piperacillin were significantly influenced by BSK II medium and incubation period and showed a marked decrease of on average 84.0% within 72 hours of incubation.

Detection of myocardial infarct extension by CK-B radioimmunoassay

Myocardial infarct extension after the acute event was defined as a second reise in the myocardial isoenzyme of serum creatine kinase (CK-B) after the initial return of CK-B to normal values. In 43 patients with acute myocardial infarcts, CK-B was measured by radioimmunoassay every 12 hours for 14 days. Nineteen patients had anterior transmural myocardial infarcts AMI, 14 had inferior transmural myocardial infarcts (IMI) and 10 had subendocardial myocardial infarcts (SEMI). Infarct extension as detectd by a second rise in serum CK-B occurred in six patients (32%) with AMI, two (14%) with IMI and two (20%) with SEMI; these differences are not statistically significant. Infarct extension for all patients combined was 23%. Four patients with AMI also had infarct extension as determined by recurrent chest pain. ECG alterations and other enzyme changes. In the other six, the infarct extension was undetected clinically. Four patients with AMI and infarct extension died within 3 weeks after hospitalization. We did not note any additional morbidity or mortality in patients with infarct extension who had IMI or SEMI. There was no significant difference in the frequency of previous myocardial infarction, history of hypertension, diabetes mellitus or smoking history in patients with and without infarct extension shown by serum CK-B isoenzyme elevations. The measurement of serum CK-B values with a quantitative and sensitive assay suggests that myocardial infarct extension occurs more commonly than clinically recognized, but the frequency of extension may be less than that reported in patients in whom precordial mapping and total serum CK values were measured to identify this phenomenon.