Inflachromene ameliorates Parkinson's disease by targeting Nrf2-binding Keap1

Parkinson's disease (PD) is the most common neurodegenerative disease characterized by movement disorder. Despite current therapeutic efforts, PD progression and the loss of dopaminergic neurons in the substantia nigra remain challenging to prevent due to the complex and unclear molecular mechanism involved. We adopted a phenotype-based drug screening approach with neuronal cells to overcome these limitations. In this study, we successfully identified a small molecule with a promising therapeutic effect for PD treatment, called inflachromene (ICM), through our phenotypic screening strategy. Subsequent target identification using fluorescence difference in two-dimensional gel electrophoresis (FITGE) revealed that ICM ameliorates PD by targeting a specific form of Keap1. This interaction led to upregulating various antioxidants, including HO-1, NQO1, and glutathione, ultimately alleviating PD symptoms. Furthermore, ICM exhibited remarkable efficacy in inhibiting the loss of dopaminergic neurons and the activation of astrocytes and microglia, which are critical factors in PD pathology. Our findings suggest that the phenotypic approach employed in this study identified that ICM has potential for PD treatment, offering new hope for more effective therapeutic interventions in the future.

Volumetric response and pattern of failure of histone altered high grade glioma in adults following management with radiation therapy

PURPOSE

H3K27M- and H3G34R-mutant gliomas are recently-classified subgroups of high-grade gliomas (HGGs) affecting younger adults. This study aimed to describe patterns of infiltration and failure, and the volumetric response of these tumours to radiotherapy.

METHODS

Patients with histone-mutant gliomas aged 16-50 years, managed from 2009 to 2021 were identified and clinical, radiological and histopathological characteristics collected. Tumour volume was assessed on MRI at diagnosis, pre-radiotherapy, month + 1, + 3 and + 5 post-radiation and at relapse.

RESULTS

Of 538 IDH1/2 wild-type HGGs, 18(15%) had a histone alteration. Eleven were H3K27M- and 7 H3G34R-mutant respectively. Median age at diagnosis was 20 years (range17-48 years). Median overall survival was 20 months (95%CI 14-29 months). Both H3K27M- and H3G34R-mutant tumours exhibited extensive T2F infiltration involving a median of 4 neuroanatomical subsites at diagnosis. Median volume of disease pre-radiotherapy on T1gd and T2F respectively was 0.5cm³ (IQR:0-1.7cm³) and 11.9 cm³ (IQR:7.5-29.6cm³) for H3K27M and 0.9cm³ (IQR:0-8.4cm³) and 43.8cm³ (IQR:25.2-86.6 cm³) for H3G34R tumours. T2F volume reduction > 50% was observed 3-months post-IMRT in 7(64%) patients with H3K27M and 1(14%) with H3G34R tumours. Fourteen patients had relapsed. Relapse was local-only, distant-only and both in 4(44%), 3(33%) and 2(22%) H3K27M-mutant and 1(20%), 2(40%), and 2(40%) H3G34R-mutant tumours. On last scan before death, leptomeningeal spread was present in 4/8(50%) and 1/5(20%) and subependymal spread in 4/8 (50%) and 0/5 H3K27M- and G34R-mutant cases respectively.

CONCLUSION

H3K27M-mutant gliomas are highly responsive to radiotherapy but exhibit high propensity for subsequent leptomeningeal and subependymal spread. H3G34R-mutant tumours exhibit lesser early volumetric response to radiotherapy and propensity for distant in-brain failure.

Targeted Protein Upregulation of STING for Boosting the Efficacy of Immunotherapy

Modulating target proteins via the ubiquitin-proteasome system has recently expanded the scope of pharmacological inventions. Stimulator of interferon genes (STING) is an auspicious target for immunotherapy. Seminal studies envisioned the importance of STING as well as the utility of its agonists in immunotherapy outcomes. Herein, we suggest UPPRIS (upregulation of target proteins by protein-protein interaction strategy) to pharmacologically increase cellular STING levels for improved immunotherapy. We discovered the small molecule SB24011 that inhibits STING-TRIM29 E3 ligase interaction, thus blocking TRIM29-induced degradation of STING. SB24011 enhanced STING immunity by upregulating STING protein levels, which robustly potentiated the immunotherapy efficacy of STING agonist and anti-PD-1 antibody via systemic anticancer immunity. Overall, we demonstrated that targeted protein upregulation of STING can be a promising approach for immuno-oncology.

Phenotype-based screening rediscovered benzopyran-embedded microtubule inhibitors as anti-neuroinflammatory agents by modulating the tubulin-p65 interaction

Neuroinflammation is one of the critical processes implicated in central nervous system (CNS) diseases. Therefore, alleviating neuroinflammation has been highlighted as a therapeutic strategy for treating CNS disorders. However, the complexity of neuroinflammatory processes and poor drug transport to the brain are considerable hurdles to the efficient control of neuroinflammation using small-molecule therapeutics. Thus, there is a significant demand for new chemical entities (NCEs) targeting neuroinflammation. Herein, we rediscovered benzopyran-embedded tubulin inhibitor 1 as an anti-neuroinflammatory agent via phenotype-based screening. A competitive photoaffinity labeling study revealed that compound 1 binds to tubulin at the colchicine-binding site. Structure-activity relationship analysis of 1's analogs identified SB26019 as a lead compound with enhanced anti-neuroinflammatory efficacy. Mechanistic studies revealed that upregulation of the tubulin monomer was critical for the anti-neuroinflammatory activity of SB26019. We serendipitously found that the tubulin monomer recruits p65, inhibiting its translocation from the cytosol to the nucleus and blocking NF-κB-mediated inflammatory pathways. Further in vivo validation using a neuroinflammation mouse model demonstrated that SB26019 suppressed microglial activation by downregulating lba-1 and proinflammatory cytokines. Intraperitoneal administration of SB26019 showed its therapeutic potential as an NCE for successful anti-neuroinflammatory regulation. Along with the recent growing demands on tubulin modulators for treating various inflammatory diseases, our results suggest that colchicine-binding site-specific modulation of tubulins can be a potential strategy for preventing neuroinflammation and treating CNS diseases.

Label-Free Target Identification Reveals the Anticancer Mechanism of a Rhenium Isonitrile Complex

Elucidation of the molecular mechanism of therapeutic agents and potential candidates is in high demand. Interestingly, rhenium-based complexes have shown a highly selective anticancer effect, only on cancer cells, unlike platinum-based drugs, such as cisplatin and carboplatin. These differences might be attributed to their different molecular targets. We confirmed that the target of tricarbonyl rhenium isonitrile polypyridyl (TRIP) complex is a protein, not DNA, using ICP-MS analysis and identified heat shock protein 60 (HSP60) as its target protein using a label-free target identification method. The subsequent biological evaluation revealed that TRIP directly inhibits the chaperone function of HSP60 and induces the accumulation of misfolded proteins in mitochondria, thereby leading to the activation of mitochondrial unfolded protein response (mtUPR)-mediated JNK2/AP-1/CHOP apoptotic pathway.

Inhibition of ACE2-Spike Interaction by an ACE2 Binder Suppresses SARS-CoV-2 Entry

The emergence of SARS-CoV-2 variants is a significant concern in developing effective therapeutics and vaccines in the middle of the ongoing COVID-19 pandemic. Here, we have identified a novel small molecule that inhibited the interactions between SARS-CoV-2 spike RBDs and ACE2 by modulating ACE2 without impairing its enzymatic activity necessary for normal physiological functions. Furthermore, the identified compounds suppressed viral infection in cultured cells by inhibiting the entry of ancestral and variant SARS-CoV-2. Our study suggests that targeting ACE2 could be a novel therapeutic strategy to inhibit SARS-CoV-2 entry into host cells and prevent the development of COVID-19.

Abstract 2816: SB1703 has therapeutic effect on syngeneic mouse model as an immune modulator in TME

Although stage I melanoma is highly curable, the prognosis of late stage melanoma is poor and treatment options are limited to immune checkpoint modulators (ICMs). In this study, we synthesized a novel small molecule, SB1703, and identified high-mobility group box (HMGB) proteins as the direct binding target proteins. SB1703 inhibited melanoma growth in B16F10 syngeneic mouse model. To elucidate the tumor growth inhibitory mechanism, we determined the changes in myeloid-derived suppressor cell (MDSC) number during drug treatment. MDSCs expand in disease states such as cancer and have immune suppressive functions. Serum HMGB1 and interleukin (IL)-6 levels were increased in vehicle administered mice and decreased in SB1703 administered mice. We examined the possibility of combinatorial treatment with SB1703 and ICMs. SB1703 showed synergistic effect with ICMs. In conclusion, SB1703 exhibited therapeutic effects against melanoma in both single and combination treatments with ICMs, which might be due to modulation of myeloid cells such as MDSCs

Citation Format: Hyo Young Kim, Hee-Jung Kim, Jae Hoon Jung, So Young Jo, Ju Hee Kim, Wansang Cho, Mingi Kim, Junhyeong Yim, Seung Bum Park. SB1703 has therapeutic effect on syngeneic mouse model as an immune modulator in TME [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 2816.

Improved Th17 Selectivity of α-Galactosylceramide via Noncovalent Interactions with Diether Moiety

α-Galactosylceramide (α-GalCer) is a typical antigen for invariant natural killer T cells that are a subset of T cells and play critical roles in regulating immune responses. To selectively induce the secretion of certain cytokines via introducing hydrogen-bonding interaction with polar amino acid residues in the binding pocket of CD1d, a series of α-GalCer analogues with diether moiety in the acyl chain were designed and synthesized. The subsequent in vitro biological evaluation of these analogues revealed the structure-activity relationship for the selective IL-17 secretion. Analogues 5 and 6 induced the significantly increased IL-17 secretion over other cytokines, suggesting protective effects against pathogens. In contrast, analogue 7 showed the highly reduced IL-17 secretion, which may indicate potential anti-inflammatory effects.

Abstract P6-17-18: Pathologic complete response (pCR) in locally advanced HER2+ (HER2+) breast cancer (BC) treated with anthracycline-free neoadjuvant therapy

Background: Response to neoadjuvant therapy is a predictor of progression-free and overall survival in HER2+. To decrease treatment associated toxicities in patients with HER2+ breast cancers we utilized a non-anthracycline regimen with pertuzumab (pert), trastuzumab (trast), and nab-paclitaxel (nab). Pre- neoadjuvant therapy biopsies were procured to evaluated possible biological predictors of pathologic complete response (pCR).

Methods: Women with locally advanced HER2 positive breast cancers were recruited from our breast cancer clinics. After obtaining informed consent for this IRB-approved trial, patients were treated with 6 cycles of pertuzumab (day 1 every 21 days [d]), and weekly trastuzumab 2 mg/kg with and nab-paclitaxel 100 mg/m2. Formalin fixed paraffin embedded (FFPE) or frozen biopsies pre-NT and post-NT were collected, along with blood samples at pre-treatment, and at the end of study for correlative analysis.

Results: Accrual is complete, with 42 of the 45 HER2+ patients assessed for pCR rate (3 too early to evaluate). The median age was 54 yrs (range 31-77 years). 12 patients were stage 3, 26 stage 2, and 1 stage 1 patient. The pCR rate was 64.2% (27/42), with 73.7% (14/19) in ER/PR negative patients and 56.5% (13/23) in ER/PR positive patients. The initial primary tumor size was similar for in those who achieved pCR and non-pCR patients (mean 4.1 cm vs 3.2 cm, respectively). Most patients required dose modifications. Grade 3 AEs reported included 6 patients with hypertension, 3 patients with hematological AEs, 3 patients with elevated LFTs, and 2 patients with diarrhea.

Conclusions: This anthracycline-free regimen in HER2+ BC can achieve promising pCR response rates, with toxicities well-managed with dose modifications. Results of correlative analysis will be presented.

Citation Format: Somlo G, Waisman J, Yuan Y, Kruper L, Frankel P, Jones V, Lusi T, Schmolze D, Yim J, Hurria A, Mortimer J. Pathologic complete response (pCR) in locally advanced HER2+ (HER2+) breast cancer (BC) treated with anthracycline-free neoadjuvant therapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-18.

Abstract P1-15-07: Phase II trial of neoadjuvant carboplatin and nab-paclitaxel in patients with locally advanced triple negative breast cancer

Background: Response to neoadjuvant therapy (NT) predicts progression-free and overall survival in triple negative breast cancer (TNBC). Carboplatin has shown efficacy in patients with TNBC. The current phase II prospective neoadjuvant trial was designed to decrease toxicities and improve efficacy.

Methods: Patients with TNBC received carboplatin (carb) and nab-paclitaxel (nab). Pre-NT biopsies were procured to evaluate for biological predictors of pathological complete response (pCR). Newly diagnosed stage II-III patients with TNBC were treated with 4 cycles of carb (AUC 6, day 1 of 28 day cycle) and weekly nab 100 mg/m2 x 16. Targeted accrual goal is 70. RNA extracted from formalin fixed paraffin embedded (FFPE) biopsies pre-NT was tested for MammaPrint/BluePrint and custom Agilent full genome microarrays for gene expression (GE, by Agendia Inc). The raw gMeanSignal was log2 transformed and normalized to the 75thpercentile for GE analysis. Association between MammaPrint/ BluePrint results and pCR was tested by Fisher exact test. The linear model from R limma package was applied. Ingenuity Pathway Analysis (IPA) was applied to assess functional pathways associated with pCR. Cellular distribution by CIBERSORT analysis was carried out to estimate the abundance of 22 different cell types in each patient sample, and test whether the distribution of cell types is different between pCR and non-responders.

Results: A total of 64 patients were enrolled. Two patients were deemed ineligible (Her2+), and three were too early, resulting in 59 patients evaluable for pathological response. The pCR rate was 47% (RCB0, 28/59). Eight patients had RCB I. RCB0 plus RCBI reached 61%. Sufficient quality RNA and DNA were available from the first 43 of 55 pts with TNBC. 44/59 (75%) required dose modifications (mostly hematologic), 5 patients had grade 3 peripheral neuropathy (PN), 3 had grade 2 PN, and 3 patients had grade 2 LFTs. In the 53 pts with GE assessment, pCR was inversely associated with luminal BluePrint type (p=0.04). With fold change >1.5 and p-value < 0.05, 36 genes were differentially expressed (DE) in TNBC. CIBERSORT analysis suggested that T-cell regulatory cells (TREGS) were associated with pCR in TNBC, and 5 cell types (plasma cells, TREGS, macrophage, dendritic cells and neutrophils) presented differently between all pCR and non-pCRs with P-value <0.05. TDP analysis to assess correlation with pCR is ongoing.

Conclusions: The combination of carboplatin and nab-paclitaxel given in the neoadjuvant setting reached a promising pCR rate of 47%. The MammaPrint non-luminal BluePrint subtype was predictive of pCR in TNBC. Preliminary analysis suggested that a 36-gene signature for TNBC was associated with pCR. CIBERSORT analysis revealed 5 cell types with different abundance between the pCR and non-responders, suggesting the need to target the tumor microenvironment.

Citation Format: Yuan Y, Frankel P, Li M, Kruper L, Jones V, Treece T, Waisman J, Yim J, Tumyan L, Schmolze D, Hurria A, Yeon C, Mortimer J, Somlo G. Phase II trial of neoadjuvant carboplatin and nab-paclitaxel in patients with locally advanced triple negative breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-15-07.

Abstract P6-15-07: Not presented

This abstract was not presented at the symposium.

Differences in Gene Expression and Gene Associations in Epicardial Fat Compared to Subcutaneous Fat

Epicardial adipose tissue (EAT) plays a role in cardiac physiology and may contribute to the development of coronary artery disease. Our objective was to determine whether there was a significant difference in gene expression in EAT compared to subcutaneous adipose tissue (SAT) and to identify potential relationships. MEDLINE and EMBASE were searched using the key terms "Epicardial Adipose Tissue" or "Epicardial Fat" in combination with "RNA", "mRNA", or "gene". The entry criteria were studies that presented primary data including expression levels of mRNA in human EAT compared with SAT and an expression of variance (SD). Genes identified by 2 or more studies were evaluated. Genes that showed significant change in expression between EAT and SAT were examined using the Gene Functional Classification analytical tool in Database for Annotation, Visualization and Integrated Discovery and cross-validated by ToppGene. Seventeen genes were identified from 25 studies. Meta-analysis showed that 10 genes (ADORA1, adiponectin, AGT, ADM, CATA, IL-1β, MCP-1, RBP-4, TNF-α, UCP-1) were significantly different in EAT. Gene Functional Classification analysis yielded 23 clusters with significant relationships. The top clusters were focused on responses to glucocorticoid stimulus, regulation of apoptosis, cellular ion homeostasis, and responses to hormone stimulus. Genetic analysis shows that EAT is discretely different from SAT. ADORA1, adiponectin, AGT, ADM, CATA, IL-1β, MCP-1, RBP-4, TNF-α, and UCP-1 may play significant roles in the unique physiology of EAT and/or its role in pathophysiology, through mechanisms as diverse as steroid hormone responses and regulation of apoptosis.

Abstract P4-21-35: Phase II trial of pertuzumab, trastuzumab, and nab-paclitaxel in patients (pts) with HER2 overexpressing (HER2+) locally advanced or inflammatory breast cancer (LABC) or untreated stage IV metastatic breast cancer (MBC)

Background: Pathologic complete response (pCR) to HER2-targeting neoadjuvant therapy (NT) predicts for improved survival (Cortazar et al, Lancet, 2014). The addition of pertuzumab to trastuzumab and docetaxel increased pCR rates, and, as first line treatment for MBC led to longer overall survival ([OS] Swain et al, NEJM 2015). Avoidance of anthracyclines in the adjuvant setting for HER2+ BC reduced the risk of secondary hematologic malignancies without a detriment to OS (Slamon et al, NEJM, 20111). Finally, nab-paclitaxel (nab) might provide an advantage over other taxanes via decreased use of steroids and may lead to increased response rates (RR). We designed a study of pertuzumab (pert), trastuzumab (trast), and nab, testing the feasibility and efficacy of this regimen in the LABC and metastatic breast cancer settings.

Materials and Methods: Pts with Stages II-III LABC received six cycles of NT with pert (day 1 q 21 days), trast, and nab 100 mg/m2 (both given IV, weekly). Pts with untreated MBC received the same regimen until progression, toxicities, or patient or physician preference led to stopping therapy. Primary endpoints included pCR (LABC) and RR and progression-free survival (PFS) in MBC. Forty pts with LABC and 25 pts with MBC were to be accrued. The study was designed to test whether the pCR rate of Neosphere (Gianni et al, Lancet Oncol, 2012, > 45.8%) and the PFS rate of CLEOPATRA (median of > 18.5 months) can be matched or exceeded. Procurement of serial samples for assessment of tumor gene expression, circulating tumor cells, miRNA, and serum DNA profiling for exploratory biomarker analysis was carried out.

Results:Twenty-two of 28 already enrolled pts with LABC (clinical stage II:15, stage III: 7) completed NT. The median age was 53 (34-77). The pCR rate was 86% (6/7) for hormone receptor negative (HR-) and 40% (6/15) for HR+ pts, with an overall pCR of 55%. Three pts without pCR following NT had residual BC with a HER2 negative phenotype. Eighteen of 22 pts required nab dose modifications. The most frequent toxicities following NT included elevated liver function tests:27%, peripheral neuropathy:23%, hematological toxicities:17%, diarrhea:18%, infusion reactions:18%. In the MBC cohort there were 13 of 16 enrolled pts with > 2 months of follow-up. The median age was 47 (31-65), 62% had HR+ disease. A CR rate of 4/13 (31%) and confirmed RR of 77% were observed. The median number of cycles with pert, trast, nab was 9 (3+ to 41); 11 of 13 pts required dose modifications or delays (3 of the delays were due to primary breast surgery performed upon response to treatment). At a median follow-up of 19 months, PFS and OS estimates are 63% (95% CI 0.09-0.93), and 89% (95% CI 0.61-1.0).

Conclusion: The non-anthracycline-containing regimen of pertuzumab, trastuzumab, and nab-paclitaxel induced a high pCR rate in HER2+ BC. PFS is encouraging in MBC. Outcome of the fully accrued cohorts inclusive of residual cancer burden scores in the LABC cohort, and correlative data with exploratory biomarker analysis will be presented.

Citation Format: Somlo G, Frankel P, Yeon C, Yuan Y, Yim J, Kruper L, Taylor L, Mortimer J, Waisman J, Jones V, Vito C, Paz B, Huria A, Li D, Gaal C, Tong T, Tumyan L. Phase II trial of pertuzumab, trastuzumab, and nab-paclitaxel in patients (pts) with HER2 overexpressing (HER2+) locally advanced or inflammatory breast cancer (LABC) or untreated stage IV metastatic breast cancer (MBC) [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-21-35.

Abstract P1-14-10: Phase II trial of neoadjuvant chemotherapy with carboplatin and nab-paclitaxel in patients with triple negative locally advanced and inflammatory breast cancer

Background: Pathologic complete response (pCR) and residual cancer burden (RCB scores of 0 [pCR] or 1[near CR]) after neoadjuvant chemotherapy (NCT) may predict for improved survival (Symmans et al. J Clin Oncol 25:4414-22, 2007). We set out to test the pCR rate with an anthracycline-free regimen of carboplatin (carb) and nab-paclitaxel (nab) in patients (pts) with triple negative breast cancer (TNBC).

Materials and Methods: Forty-nine pts with stages II-III BC were to receive carb (AUC 6) on day 1 of a 28 day cycle, and nab 80 mg/m2 weekly, for a total of 4 cycles. Core biopsies were performed prior to NCT. Blood procurement for circulating tumor cell (CTC) analysis using the CellSearch platform was carried out pre-treatment, mid-treatment, and at surgery. We set out to assess the predictive value of Mammaprint (poor vs. good), BluePrint (basal, vs. luminal, vs. HER2) molecular subtype as well as microarray RNA and miRNA profiling, for pCR. Responses were also dichotomized as complete or near complete response (Symmans RCB scores of 0-1) vs. suboptimal response (RCB score > 1).

Results: The median age was 53 (28-75). Pts presented with clinical stages II (63%) and III (37%). So far, 38 of the 49 pts accrued between 2/2012 and 6/2015, have undergone surgery, 68% of whom underwent modified radical mastectomy. The pCR rate (breast and lymph nodes in CR) was 53%, and RCB 0 and 1 were seen in 68% of pts. Toxicites included grade ¾ anemia (45%), thrombocytopenia (13%) and neutropenia (53%,1 pt with neutropenic fever). Dose adjustments were needed in over 80% of pts. Grades 2 or 3 peripheral neuropathy were seen in 8% each, and grades 3-4 fatigue (13%), hypokalemia (3%), and hyponatremia (3%) were observed. The median number of CTCs (pre-NCT) observed in 7 CTC positive pts of the first 27 pts who completed surgery was 1 (0-7), and 2 of the 7 pts continued to have CTCs at the time of surgery (1 CTC each), while 2 pts without CTCs pre-NCT had CTCs (1 each) detected at surgery. The final pt enrolled is expected to complete surgery by 10/2015. Results of sequential CTC assessments, MammaPrint/Blueprint and RNA/miRNA analysis of pre- and post-treatment specimens and their correlation with pCR will be presented.

Conclusion: The non-anthracycline-containing regimen of carb and nab-paclitaxel induced a high pCR rate in TNBC, in preliminary analysis. Ongoing profiling may allow for future subset-specific modification of this regimen to increase pCR across all molecular subtypes of TNBC.

Citation Format: Somlo G, Chung S, Frankel P, Hurria A, Koehler S, Kruper L, Mortimer JE, Paz B, Robinson K, Taylor L, Vito C, Waisman J, Yeon C, Yim J, Yuan Y, Tong T. Phase II trial of neoadjuvant chemotherapy with carboplatin and nab-paclitaxel in patients with triple negative locally advanced and inflammatory breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P1-14-10.

Abstract P6-13-17: The combination of eribulin and everolimus results in enhanced suppression of tumors in mouse models of triple negative breast cancer

INTRODUCTION. Triple negative breast cancer (TNBC) is an aggressive form of breast cancer with poor overall and relapse free survival. TNBC does not have targeted or matched therapies. Patients have worse outcomes after chemotherapy than with other subtypes of breast cancer. TNBC accounts for 12-17% of all breast cancers, leaving an unmet need for targeted therapy. Efforts to profile these tumors have revealed several potential targets.

The PI3K/AKT/mTOR pathway is a signal transduction pathway that links growth related hormone receptor interaction to downstream targets such as AKT and mammalian target of rapamycin (mTOR). This pathway targets affect cell proliferation, survival, and apoptosis. Patients with TNBC have high levels of AKT expression and activation of this pathway.

Microtubule-targeting agents have been used in TNBC. Eribulin mesylate is a microtubule-targeting agent with benefits in treating taxane and anthracycline refractory breast cancer via a microtubule targeting anti-mitotic mechanism. It has been approved for the treatment of TNBC in heavily pretreated patients.

Despite targeted therapy, breast cancer cells can grow resistant. Targeting multiple cancer growth pathways has been used in patients that progress on therapy or fail to respond. We hypothesized that targeting both mitotic blockade and PI3K/AKT/mTOR pathway may provide enhanced suppression of TNBC growth in both syngeneic and xenogeneic mouse models.

MATERIALS AND METHODS. MDA-MB-468 is a human TNBC cell line. 4T1 is a highly metastatic mouse TNBC cell line derived from a spontaneously arising Balb/c mammary tumor. 4T1 and MDA-MB-468 tumor cells were injected into the mammary fat pad of female Balb/c and NOD/SCID/IL2Rgamma null (NSG) mice (with matrigel) respectively. After tumors were formed Balb/c mice were treated three times per week with vehicle, eribulin (0.75 mg/kg i.v.), RAD001 (5 mg/kg via oral gavage) or a combination of both. NSG mice were treated three times per week with vehicle, eribulin (0.5 mg/kg i.v.), RAD001 (5 mg/kg by oral gavage), or a combination of both. Tumor volumes and body weights were measured. Student t-test was used to compare the means of two groups and determine the p value (p<0.05 is significant). N=3-8 per group.

Table I. 4T1 mouse breast cancer modelTreatmentTumor Volume (mm3)+/-SEMVehicle511.6+/-56.82Eribulin445.6+/-92.17Everolimus324.9+/-24.55Combination171.4+/-16.07 p valueCombination vs. Vehicle0.0001Combination vs. Eribulin0.01Combination vs. Everolimus0.001

Table II. MDA-MB-468 human breast cancer cells in immune deficient mice.TreatmentTumor Volume (mm3)+/-SEMVehicle966.8+/-69.2Eribulin67.81+/-11.79Everolimus830.6+/-156.3Combination31.37+/-3.37 p valueCombination vs. Eribulin0.041Combination vs. Everolimus0.0076

RESULTS. In the 4T1 syngeneic breast cancer mouse model, the combination of Eribulin and Everolimus resulted in marked suppression of tumor growth which was statistically significant versus vehicle treatment alone, or Eribulin or Everolimus alone (Table I). In the MDA-MB-468 model, the combination of Eribulin and Everolimus demonstrated marked suppression of tumor growth which was statistically significant compared to either agent alone (Table II).

Citation Format: Marcinkowski E, Luu T, Yuan Y, Mortimer J, Leong L, Portnow J, Xing Q, Wen W, Yim J. The combination of eribulin and everolimus results in enhanced suppression of tumors in mouse models of triple negative breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-13-17.

Structural modelling and molecular characterization of omega-class glutathione S-transferase 2 from Drosophila melanogaster

Glutathione S-transferase omega (GSTO) is a recently identified Glutathione S-transferase (GST), and it has several known functions and variable distribution patterns in many organisms. In Drosophila, GstO2 exists as two isoforms, GstO2A and GstO2B. Despite the high sequence homology between the two GstO2 isoforms, they have different physiological functions. In the present study, we characterized the structural and molecular properties of Drosophila melanogaster GstO2 isoforms. Homology modelling of GstO2s using I-TASSER servers for protein structure and function prediction revealed that the two GstO2s have different electropotential surface distributions and different shapes of the substrate-binding sites. The recombinant GstO2s have native molecular weights of ∼60 kDa. GstO2s have similar optimum conditions for enzymatic reactions at pH 8.0 and 40 °C. The kinetic parameters of the reduction of dehydroascorbate by these two GstO2s were determined. Collectively, our results provide structural insights into the different substrate profiles of the GstO2 isoforms.

Abstract P2-09-17: Limited Gene Expression Profiling as Predictor of Response to Neoadjuvant Chemotherapy (NCT) with Docetaxel, Doxorubicin, Cyclophosphamide (TAC), or AC and Nab-Paclitaxel and Carboplatin +/− Trastuzumab in Patients (pts) with Locally Advanced (LABC) Stage II-III and Inflammatory Breast Cancer (IBC)

Background: Pathologic complete response (pCR) following neoadjuvant therapy (NCT) may predict for improved survival. Hence, more effective and individualized/targeted NCT regimens in conjunction with molecular markers that predict for both response and/or resistance are needed. Materials and Methods: 119 evaluable pts (121 enrolled) with stages II/III LABC/IBC were prospectively randomized to receive 6 cycles of docetaxel 75 mg/m2, doxorubicin 50 mg/m2, cyclophosphamide 500 mg/m2 with filgrastim support (TAC, arm A) versus a novel regimen of A 60 mg/m2 and C 600 mg/m2 given every 2 weeks x 4, followed by 3 weekly doses of carboplatin (AUC 2) and nab-paclitaxel 100 mg/m2 repeated as 28 day cycles x 3 (arm B). Pts with HER2 overexpressing (HER2+) BC received NCT similar to arm B, but with the addition of 12 weekly doses of trastuzumab given together with carboplatin and nab-paclitaxel (arm C). Core biopsies were performed prior to NCT and samples from 10 micron thick slides of formalin-fixed and paraffin-embedded (FFPE) breast cancer tissue were microdissected, and RNA was extracted for assessment of gene expression by RT-PCR for a panel of genes involved in cell proliferation, tumor suppression, DNA repair, and apoptosis. The following genes were evaluated: HER2/neu, IGF-1R, JAK2, STAT3, EGFR, BRCA1 and 2, PARP1, ERCC1, Topoisomerase 2-alpha, BBC3 (PUMA), p21, p27, IRF1, Beta-catenin, and SPARC, with actin as control. Responses were separated as complete or other response, and the Wilcoxon test was applied. Results: Neoadjuvant response assessment and sufficient amount of RNA following microdissection of primary tumor slides were available in 66/121 pts (55%). These 66 pts had similar characteristics to the entire cohort of enrolled pts. The median age was 51 yrs (range 30-69), and pts were treated for stage II/III BC (N=32, N=34, respectively, with 10 IBC cases). 37 pts were treated on Arms A and B (HER2- cohorts), and 29 on arm C (HER2+ cohort). pCR rates were 5/37 (14%) in groups A and B (of this set) combined, and 14/29 (48%) in group C (HER2+). For all arms/pts combined, overexpression of HER2, EGFR, and BRCA2, and low expression of p27, and IGFR1 were observed in pts with pCR, in comparison to pts not achieving pCR (P<0.05). When the analysis was restricted to HER2 negative cases (Arms A and B), BRCA2, JAK2 overexpression, and low expression of IGF1R were associated with pCR (P<0.05). Conclusion: Limited gene array analysis from microdissected FFPE specimens procured prior to NCT is feasible, and there is sufficient evidence in this limited data set to suggest that the specifc gene expression levels tested may play an important role in determining response to NCT both in HER2+ and HER2-, locally advanced, and inflammatory breast cancer.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-09-17.

Basal-, Luminal-, and HER2- Molecular Subtype, and the MammaPrint 70-Gene Signature as Predictors of Response to Neoadjuvant Chemotherapy (NCT) with Docetaxel, Doxorubicin, Cyclophosphamide (TAC), or AC and Nab-Paclitaxel and Carboplatin +/- Trastuzumab in Patients (Pts) with Stage II-III and Inflammatory Breast Cancer (BC)

Background: Pathologic complete response (pCR) and minimal residual cancer burden (RCB scores of 0 [pCR]-1[near CR]) after NCT may predict for improved survival (Symmans et al. J Clin Oncol 25:4414-22, 2007). Hence, improved NCT regimens in conjunction with molecular markers that predict for both response and/or resistance are needed. Materials and Methods: 115 pts with stages II-III BC were to be prospectively randomized to receive 6 cycles of docetaxel 75 mg/m2, doxorubicin 50 mg/m2, cyclophosphamide 500 mg/m2 with filgrastim support (TAC, arm A) versus a novel regimen of A 60 mg/m2 and C 600 mg/m2 given every 2 weeks x 4, followed by 3 weekly doses of carboplatin (AUC 2) and nab-paclitaxel 100 mg/m2 repeated as 28 day cycles x 3 (arm B). Pts with HER2 + BC received NCT similar to arm B, but with the addition of 12 weekly doses of trastuzumab given together with carboplatin and nab-paclitaxel (arm C). Core biopsies were performed prior to NCT and were preserved fresh frozen. 70-gene (MammaPrint™) profiling and 80-gene profiling (van de Vijver et al. NEJM 347:1999-2009, 2002) to categorize all tumors for basal-, HER2-, and luminal subtypes were carried out. We set out to assess the predictive value of Mammaprint scores (poor vs. good), as well as basal, vs. luminal, vs. HER2 molecular subtype profiling, for response to treatment on arms A vs. B vs. C. Responses were dichotomized as complete or near complete response (Symmans RCB scores of 0-1) vs. suboptimal response (RCB score > 1). Results: Sufficient amount of BC tissue and good quality RNA for gene array assessment were procured in 64% of the first 90 patients who have undergone pre-treatment core biopsies, and then proceeded to NCT, followed by definitive surgery. Here we report on the first 50 pts with complete set of data analyzed. The median age was 50 years (range:31-69). Pts were treated for stage II (49%) and III locally advanced (41%), and inflammatory BC (10%). By gene profiling, 28% of the tumors were HER2-type (vs. 38% by IHC 3+, or FISH, representing all pts treated on arm C), 26% basal-type, 42% luminal-type, and 4% borderline luminal-type. Poor-prognosis signature by the 70-gene (MammaPrint) assay was observed in 74% of pts: 92% of HER2-type, 100% of basal-type, and 52% of luminal-type tumors were characterized as poor-risk by the 70-gene assay. Following NCT, Symmans RCB scores of 0-1 were observed in 71% of pts with HER2-type, in 38% with basal-type, and 28% of pts with luminal-type molecular subtype characteristics. Conclusion: BC with HER2- and basal-molecular subtypes are more likely to respond to NCT and is frequently associated with poor-risk characteristics as determined by the 70-gene assay. The complete analysis of correlations among response to specific sets of NCT, molecular subtype, and 70-gene assay results in the entire pt population will be presented.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 2026.

Transcranial magnetic stimulation in ALS: utility of central motor conduction tests

OBJECTIVE

To investigate transcranial magnetic stimulation (TMS) measures as clinical correlates and longitudinal markers of amyotrophic lateral sclerosis (ALS).

METHODS

We prospectively studied 60 patients with ALS subtypes (sporadic ALS, familial ALS, progressive muscular atrophy, and primary lateral sclerosis) using single pulse TMS, recording from abductor digiti minimi (ADM) and tibialis anterior (TA) muscles. We evaluated three measures: 1) TMS motor response threshold to the ADM, 2) central motor conduction time (CMCT), and 3) motor evoked potential amplitude (correcting for peripheral changes). Patients were evaluated at baseline, compared with controls, and followed every 3 months for up to six visits. Changes were analyzed using generalized estimation equations to test linear trends with time.

RESULTS

TMS threshold, CMCT, and TMS amplitude correlated (p < 0.05) with clinical upper motor neuron (UMN) signs at baseline and were different (p < 0.05) from normal controls in at least one response. Seventy-eight percent of patients with UMN (41/52) and 50% (4/8) of patients without clinical UMN signs had prolonged CMCT. All three measures revealed significant deterioration over time: TMS amplitude showed the greatest change, decreasing 8% per month; threshold increased 1.8% per month; and CMCT increased by 0.9% per month.

CONCLUSIONS

Transcranial magnetic stimulation (TMS) findings, particularly TMS amplitude, can objectively discriminate corticospinal tract involvement in amyotrophic lateral sclerosis (ALS) from controls and assess the progression of ALS. While central motor conduction time and response threshold worsen by less than 2% per month, TMS amplitude decrease averages 8% per month, and may be a useful objective marker of disease progression.

Drosophila homolog of APP-BP1 (dAPP-BP1) interacts antagonistically with APPL during Drosophila development

beta-Amyloid precursor protein binding protein 1 (APP-BP1) was previously identified based on its binding to the carboxyl terminal of beta-amyloid precursor protein. In this report, we have discovered that a mutation of dAPP-BP1 (Drosophila ortholog of APP-BP1) hinders tissue development, causes apoptosis in imaginal disc cells, and blocks the NEDD8 conjugation pathway. We show that dAPP-BP1 specifically binds the intracellular domain of APP-like protein (APPL). The dAPP-BP1 mutation partially suppresses the abnormal macrochaete phenotype of Appl(d), while overexpression of dAPP-BP1 causes abnormal macrochaetes. When APPL is overexpressed, the normal bristle pattern in the fly thorax is disturbed and apoptosis is induced in wing imaginal discs. APPL overexpression phenotypes are enhanced by reducing the level of dAPP-BP1. APPL overexpression is shown to inhibit the NEDD8 conjugation pathway. APPL-induced apoptosis is rescued by overexpression of dAPP-BP1. Our data suggest that APPL and dAPP-BP1 interact antagonistically during Drosophila development.

Expression of the seqA gene is negatively modulated by the HU protein in Escherichia coli

The SeqA protein acts as a regulator of chromosomal replication initiation in Escherichia coli by sequestering hemi-methylated oriC, effectively blocking methylation and therefore preventing rapid re-initiation. The level of SeqA protein is maximal at mid-log phase and decreases when cells enter late-log phase. In hup mutants that lack the HU protein, the maximal seqA expression is also seen at mid-log phase, but seqA expression, as well as SeqA levels and activity, is increased by up to four fold relative to that in the wild type. These results suggest that the HU protein functions as a negative modulator of seqA expression.

Molecular characterization of Drosophila melanogaster myo-inositol-1-phosphate synthase

We have isolated and characterized a cDNA encoding Drosophila melanogaster myo-inositol-1-phosphate synthase (INOS). The deduced Drosophila INOS protein is 50% identical to the Saccharomyces cerevisiae INO1 gene. The putative active site residues are well conserved in Drosophila INOS protein. Southern blot analysis shows that Drosophila INOS gene is a single copy gene. Northern blot analysis reveals that Drosophila INOS gene expresses a 2.0-kb transcript that is more abundant in the head than the body, suggesting that it may be involved in brain function. The recombinant Drosophila INOS protein was expressed in Escherichia coli and the purified protein has proved to have a myo-inositol-1-phosphate synthase activity.

5'-Flanking sequence and promoter activity of the rabbit neuronal nitric oxide synthase (nNOS) gene

We have isolated a rabbit neuronal nitric oxide synthase (nNOS) cDNA encoding a protein of 1,435 amino acids. Using the cDNA clones as probes, the 5'-flanking region of the nNOS gene was isolated from a rabbit genomic DNA library. 5'RACE and primer extension analysis of rabbit brain total RNA mapped multiple transcription initiation sites localized 474-487 bp upstream from the translation start codon. Analysis of 5,197 bp of the 5'-flanking sequence revealed that the rabbit nNOS gene promoter lacks canonical TATA or CCAAT boxes and, instead, contains a GC-rich region and multiple Sp1 sites. Farther from the +1start, various putative cis-elements including AP-1, AP-4, NF-kappaB, STAT, CREB, C/EBP and c-Myc were observed. The functional promoter activity of the 5'-flanking region was demonstrated by its ability to drive the expression of a beta-galactosidase reporter gene in several cell types. Serial deletion analysis of the promoter region revealed that the -291 to -172 region, which contains two Sp1 sites, is essential for basal transcriptional activity. These results suggest that the rabbit nNOS promoter contains characteristics of inducible genes.

Epithelial cell-specific laminin 5 is required for survival of early thymocytes

The gene LamC2 encoding the gamma2 chain of laminin 5, an epithelial cell-specific extracellular matrix protein, was identified in a PCR-based subtracted cDNA library from mouse thymic stromal cells. The mRNA existed in two alternative forms (5.1 and 2.4 kb). The full-length message was highly expressed in SCID thymus and in a nurse cell line, but not in other thymic epithelial cell lines, while the short form was more widely expressed. In situ hybridization and immunohistochemical staining revealed laminin 5 expression mostly in the subcapsular region of the adult thymus. Addition to fetal thymic organ cultures of a cell adhesion-blocking mAb to the alpha3 chain of laminin 5 interrupted T cell development. There was a 40% reduction in the total yield of thymocytes, and the most profound decrease (75-90%) was seen in the CD25+CD44+ and CD25+CD44-subsets of the CD4-CD8- double negative fraction. Most of the surviving double negative thymocytes expressed Sca-1, and there were significant increases in the number of cells with CD69 expression and in the fraction of annexin V-stained cells. None of these changes were observed with a nonblocking anti-laminin alpha3 chain mAb. These results suggest that the interaction between double negative thymoctyes and laminin 5 made by subcapsular epithelial cells is required for the survival and differentiation of mouse thymocytes.

Molecular characterization of Drosophila melanogaster dihydropteridine reductase

Dihydropteridine reductase (DHPR) catalyzes the NAD(P)H-mediated reduction of quinonoid dihydropteridine as a part of pterin-dependent aromatic amino acid hydroxylation. We isolated a fragment of Drosophila DHPR gene by PCR using degenerate primers. By screening a cDNA library, we obtained full-length clones. The predicted amino acid sequence of the Drosophila DHPR protein was highly homologous to other species including human and mouse. In particular, the Tyr-(Xaa)(3)-Lys motif, known as the NAD(P)H binding domain, and most amino acids relevant to quinonoid dihydropteridine binding site are identical to human DHPR. The recombinant DHPR protein expressed in Escherichia coli showed DHPR enzyme activity. Northern blot analysis revealed two transcripts of 1.1 and 0.9 kb. Genomic DNA sequencing revealed that the gene consists of two exons interrupted by a single 96-bp intron. The two transcripts have alternative promoters, both having no putative TATA box or CAAT box, but sharing a common poly(A)(+) signal. The existence of two alternative promoters suggests that each transcript be regulated independently through different stimuli. Further study is needed to examine the expression and function of the two alternative transcripts.

Signaling pathways to the assembly of an interferon-beta enhanceosome. Chemical genetic studies with a small molecule

Small molecules that modulate specific protein functions are valuable tools for dissecting complex signaling pathways. Here, we identified a small molecule that induces the assembly of the interferon-beta (IFN-beta) enhanceosome by stimulating all the enhancer-binding activator proteins: ATF2/c-JUN, IRF3, and p50/p65 of NF-kappaB. This compound stimulates mitogen-activated protein kinase kinase kinase 1 (MEKK1), which is a member of a family of proteins involved in stress-mediated signaling pathways. Consistent with this, MEKK1 activates IRF3 in addition to ATF2/c-JUN and NF-kappaB for the assembly of the IFN-beta enhanceosome. MEKK1 activates IRF3 through the c-JUN amino-terminal kinase (JNK) pathway but not the p38 and IkappaB kinase (IKK) pathway. Taken together with previous observations, these results implicate that, for the assembly of an IFN-beta enhanceosome, MEKK1 can induce IRF3 and ATF2/c-JUN through the JNK pathway, whereas it can induce NF-kappaB through the IKK pathway. Thus, specific MEKK family proteins may be able to integrate some of multiple signal transduction pathways leading to the specific activation of the IFN-beta enhanceosome.

Fringe forms a complex with Notch

The Fringe protein of Drosophila and its vertebrate homologues function in boundary determination during pattern formation. Fringe has been proposed to inhibit Serrate-Notch signalling but to potentiate Delta-Notch signalling. Here we show that Fringe and Notch form a complex through both the Lin-Notch repeats and the epidermal growth factor repeats 22-36 (EGF22-36) of Notch when they are co-expressed. The Abruptex59b (Ax59b) and AxM1 mutations, which are caused by missense mutations in EGF repeats 24 and 25, respectively, abolish the Fringe-Notch interaction through EGF22-36, whereas the l(1)N(B) mutation in the third Lin-Notch repeat of Notch abolishes the interaction through Lin-Notch repeats. Ax mutations also greatly affect the Notch response to ectopic Fringe in vivo. Results from in vitro protein mixing experiments and subcellular colocalization experiments indicate that the Fringe-Notch complex may form before their secretion. These findings explain how Fringe acts cell-autonomously to modulate the ligand preference of Notch and why the Fringe-Notch relationship is conserved between phyla and in the development of very diverse structures.

Identification of Mad as a repressor of the human telomerase (hTERT) gene

Activation of telomerase, which has been frequently associated with cellular immortality, may constitute a key step in the development of human cancer. De-repression in the expression of its catalytic subunit hTERT gene has been proposed to directly link to the telomerase activation in tumor cells. Little is known about the mechanism how the hTERT gene is repressed in telomerase-negative mortal cells. This study was conducted, using an expression cloning approach, with the aim of identifying the gene(s) responsible for repressing the hTERT gene expression. Using this genetic screen, we isolated the transcription factor Mad as a repressor. Mutation of its DNA binding sites caused significant de-repression of hTERT promoter activity in mortal cells. This Mad-mediated repression of the hTERT promoter in mortal cells was counteracted by ectopic expression of Myc. The antagonism between Mad and Myc was also observed with an endogenous hTERT promoter. Their potential roles in differential hTERT promoter activities were further supported by the relative amounts of Mad and Myc proteins detected in immortal and mortal cells. Thus, Mad may be a direct negative regulator of hTERT in mortal cells and this repression mechanism can be inhibited by induction of Myc in immortal cells.

Chemotherapeutic DNA-damaging drugs activate interferon regulatory factor-7 by the mitogen-activated protein kinase kinase-4-cJun NH2-terminal kinase pathway

Chemotherapeutic drugs and energy-rich radiation cause DNA damage, inducing signaling pathways for apoptotic cell death or cell growth arrest. The tumor suppressor gene p53 plays the critical role in the regulation of these DNA damage responses. Human tumor cells can become resistant to chemotherapy through functional inactivation of p53. Thus, it is important to identify p53-independent DNA damage signaling pathways. Here, treatment of cells with chemotherapeutic drugs or UV irradiation potentiated the transcriptional activity of IFN regulatory factor-7 (IRF7), inducing its phosphorylation and its nuclear translocation. Furthermore, IRF7 was activated by the c-Jun NH2-terminal kinase (JNK) in response to DNA-damaging agents. Activation of JNK by mitogen-activated protein kinase kinase-4 stimulated the transcriptional activity of IRF7 and induced its translocation into the nucleus. Thus, activation of IRF7 through the JNK signaling pathway may play a role in the transcriptional regulation of genes in response to DNA-damaging agents.

Involvement of retinoblastoma protein in p27Kip1-induced apoptosis

p27Kip1, a cyclin-dependent kinase (CDK) inhibitor, plays a critical role in cell cycle regulation. Expression of p27Kip1 is shown to increase during apoptosis in mammalian cells. Here, to directly address the role of p27Kip1 in apoptosis, p27Kip1 is overexpressed in human SK-Hep1 hepatoma cells. This leads to apoptotic cell death and this reduces protein, but not mRNA, levels of the retinoblastoma (Rb). Consistently, accumulation of Rb protein blocks p27Kip1-mediated apoptosis. These studies demonstrate an involvement of Rb in the apoptotic cell death which is induced by overexpression of p27Kip1.

The Wilms' tumor 1 tumor suppressor gene represses transcription of the human telomerase reverse transcriptase gene

Regulation of the human telomerase reverse transcriptase (hTERT) gene is the primary determinant for telomerase enzyme activity, which is found in tumor cells but is largely absent from normal somatic cells. Recent studies have shown that Myc protein can transcriptionally activate the hTERT gene. However, little is known about the repression mechanism of the hTERT gene and telomerase enzyme. Here, we developed an expression cloning strategy to identify cDNAs whose products can repress hTERT promoter activity in telomerase-positive immortal cells. Using this screen, we isolated the Wilms' tumor 1 suppressor gene (WT1). WT1 can repress hTERT promoter activity in 293 kidney cells. The WT1 binding site on the hTERT promoter was identified by deletional analysis. Alteration of the WT1 binding site markedly derepresses transcription from an isolated hTERT promoter by inhibiting interaction of WT1 with DNA. These specific repression effects of WT1 were not observed in HeLa cells, which express no endogenous WT1. Furthermore, we show that WT1 can repress the endogenous hTERT promoter and telomerase enzyme activities. These results suggest that WT1 may be a transcriptional repressor of the hTERT gene, at least in some specific cells.

Activation of interferon regulatory factor 3 in response to DNA-damaging agents

Genotoxic stress triggers signal transduction pathways that mediate either the protection or apoptosis of affected cells. The interferon regulatory factors (IRFs) are involved in a wide range of host defense mechanisms against environmental stresses. Treatment with DNA-damaging agents, including doxorubicin and UV radiation, caused phosphorylation of the IRF3 transcription factor. Phosphorylation of IRF3 induced its interaction with the transcriptional co-activator cAMP-response element binding protein-binding protein. Furthermore, genotoxic stress-induced phosphorylation of IRF3 resulted in its movement from the cytoplasm to the nucleus, where it activated transcription from its binding site. These observations suggest that IRF3 plays a role in the defensive responses induced by genotoxic stress.

In vivo and in vitro analyses of Myc for differential promoter activities of the human telomerase (hTERT) gene in normal and tumor cells

Induction of the catalytic subunit of human telomerase, hTERT, plays a critical role in the activation of telomerase during tumorigenesis. Here, we isolate the hTERT gene promoter and define the functional promoter region, which is inactive in normal cells but active in tumor cells. Myc directly interacts with the hTERT promoter and activates its transcription both in vivo and in vitro. Activation or repression of Myc can alter hTERT promoter activities in normal or tumor cells. Furthermore, we detect high levels of Myc protein in tumor cells compared with normal cells. The ability of Myc to modulate the activity of the hTERT promoter and, hence, the telomerase enzyme may contribute to its ability to promote tumor formation.

Human cytomegalovirus IE1 protein activates AP-1 through a cellular protein kinase(s)

During human cytomegalovirus (HCMV) infection, a rapid increase in AP-1 activity is detected. In this study, activation of transcription from promoters containing AP-1-binding sites by the IE1 protein of HCMV was examined. In transient transfection assays with reporter plasmids, it was found that IE1 strongly induced AP-1-driven transcription. Cells stably expressing IE1 also showed higher levels of AP-1 activity than did control cells. IE1 expression did not raise levels of c-jun and c-fos RNA, as determined by quantitative RT-PCR. AP-1 induction by IE1 was blocked efficiently by protein kinase inhibitors in a cell type-dependent manner; for example, by staurosporine in the human microglial cell line U373MG and by H7 in the human promonocytic cell line U937. IE1-driven activation of AP-1 was increased dramatically by mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinase 1 (MEKK1). The results of this study indicate that IE1 activates AP-1 at the post-transcriptional level and that MEKK1 may play an important role in this process.

Crystallographic and kinetic investigations on the mechanism of 6-pyruvoyl tetrahydropterin synthase

The enzyme 6-pyruvoyl tetrahydropterin synthase (PTPS) catalyses the second step in the de novo biosynthesis of tetrahydrobiopterin, the conversion of dihydroneopterin triphosphate to 6-pyruvoyl tetrahydropterin. The Zn and Mg-dependent reaction includes a triphosphate elimination, a stereospecific reduction of the N5-C6 double bond and the oxidation of both side-chain hydroxyl groups. The crystal structure of the inactive mutant Cys42Ala of PTPS in complex with its natural substrate dihydroneopterinetriphosphate was determined at 1.9 A resolution. Additionally, the uncomplexed enzyme was refined to 2.0 A resolution. The active site of PTPS consists of the pterin-anchoring Glu A107 neighboured by two catalytic motifs: a Zn(II) binding site and an intersubunit catalytic triad formed by Cys A42, Asp B88 and His B89. In the free enzyme the Zn(II) is in tetravalent co-ordination with three histidine ligands and a water molecule. In the complex the water is replaced by the two substrate side-chain hydroxyl groups yielding a penta-co-ordinated Zn(II) ion. The Zn(II) ion plays a crucial role in catalysis. It activates the protons of the substrate, stabilizes the intermediates and disfavours the breaking of the C1'C2' bond in the pyruvoyl side-chain. Cys A42 is activated by His B89 and Asp B88 for proton abstraction from the two different substrate side-chain atoms C1', and C2'. Replacing Ala A42 in the mutant structure by the wild-type Cys by modelling shows that the C1' and C2' substrate side-chain protons are at equal distances to Cys A42 Sgamma. The basicity of Cys A42 may be increased by a catalytic triad His B89 and Asp B88. The active site of PTPS seems to be optimised to carry out proton abstractions from two different side-chain C1' and C2' atoms, with no obvious preference for one of them. Kinetic studies with dihydroneopterin monophosphate reveal that the triphosphate moiety of the substrate is necessary for enzyme specifity.

An analysis of two tandem promoters of the Drosophila purple gene

We have analyzed two tandem promoters, separated by only about 400 bp, of the purple (pr) gene of Drosophila melanogaster, by fusing them to the firefly luciferase reporter gene and employing a transient expression assay with Drosophila S2 cells. Both the distal promoter and the proximal promoter were found to function in S2 cells and an about 700 bp long region (-270 to +421), containing both promoters, was sufficient to effect maximal promoter activity. When the two promoters were analyzed separately, the distal promoter was found to be much stronger in its function than the proximal promoter. At least three different kinds of cis elements near the transcription start site appear to play crucial roles in driving constitutive expression from the distal promoter. On the other hand, only a single cis element, which may play a role in tissue-specific expression, appears to be important for the activity of the proximal promoter in S2 cells. We propose that the clustering of important cis elements near the transcription start sites may be responsible for the selective regulation of the two tandem promoters.

Isolation and characterization of the Drosophila melanogaster cDNA encoding the sepiapterin reductase

We have isolated and characterized the cDNA encoding Drosophila melanogaster sepiapterin reductase (SR). The amino acid sequence deduced from the cDNA sequence was 29% identical to those of mammalian SRs. The active site residues proposed from the three-dimensional structure of mouse SR are well conserved in Drosophila SR. The protein-coding region of the cDNA was expressed in Escherichia coli as a histidine fusion protein, and the resulting recombinant protein proved to have SR activity. The SR activity of the recombinant protein was inhibited by two indoleamines, N-acetyl serotonin and melatonin. Southern analysis suggests that the Drosophila SR gene is encoded by a single copy gene. RNA blot analysis revealed that the gene expresses 1.5 kb mRNA in both adult heads and bodies.

Molecular characterization of the Drosophila melanogaster gene encoding the pterin 4alpha-carbinolamine dehydratase

We have isolated and characterized the cDNA and the genomic DNA encoding Drosophila melanogaster pterin 4alpha-carbinolamine dehydratase (PCD). The amino acid sequence deduced from the cDNA sequence was very similar to those of PCDs previously reported in other species (19-57% identity). The protein coding region of the cDNA was expressed in E. coli as a histidine fusion protein, and the expressed protein proved to have PCD activity. The characterization of the Drosophila genomic clone revealed that the Drosophila PCD gene is interrupted by two introns. The potential promoter region, deduced from the determination of the transcription start point (tsp), lacks the distinct TATAAA box consensus sequence.

Cloning and structure of a rabbit protein inhibitor of neuronal nitric oxide synthase (PIN) gene and its pseudogene

Neuronal nitric oxide synthase (nNOS), the biosynthetic enzyme for the free radical neurotransmitter nitric oxide, was found to be inhibited by the protein inhibitor of nNOS, designated PIN (Jaffrey, S.R. and Snyder, S.H., (1996) Science 274, 774-777). The cDNA clone encoding a rabbit PIN was isolated, and the translated PIN protein was89 amino acid long sharing 100% of its deduced amino acid sequence with rat PIN. Using a radiolabelled riboprobe derived from the rabbit PIN cDNA, the rabbit PIN gene was isolated from a rabbit genomic library and the structural organization of the gene was determined. The gene contains three exons separated by two introns spanning approx. 2.3kb of genomic DNA. 5' RACE analysis mapped the transcriptional initiation site 98bp upstream of the initiator methionine codon. Characterization of the 5' flanking genomic region revealed that the rabbit PIN promoter is TATA-less, but contains a CCAAT box as well as various putative transcription factor-binding elements. The 3' untranslated region contains consensus polyadenylation signal (AATAAA). We also isolated an intronless gene with 93% nucleotide sequence similarity to the rabbit PIN cDNA. Sequence analysis indicates that the open reading frame was interrupted by a premature stop codon and frameshift which resulted in a processed pseudogene of the rabbit PIN.