The National Center for Advancing Translational Sciences' Intramural Training Program and Fellow Career Outcomes

The National Center for Advancing Translational Sciences (NCATS) defines translational science as "the field of investigation focused on understanding the scientific and operational principles underlying each step of the translational process." A major goal of translational science is to determine commonalities across projects to identify principles for addressing persistent bottlenecks in this process. To meet this goal, translational scientists must be conversant in multiple disciplines, work in teams, and understand the larger translational science ecosystem. The development of these skills through translational science training opportunities, such as the translational science training offered by the NCATS intramural research program, prepares fellows for a variety of career options. The unique structure of the NCATS intramural program and the career outcomes of its alumni are described herein to demonstrate the distinct features of this training environment, the productivity of fellows during their time in training, and how this prepares fellows to be competitive for a variety of science careers. To date, the NCATS intramural research program has trained 213 people, ranging from high school to postdoctoral levels. These alumni have transitioned into a wide array of career functions, types, and sectors.

Resistance to the CHK1 inhibitor prexasertib involves functionally distinct CHK1 activities in BRCA wild-type ovarian cancer

High grade serous ovarian cancer (HGSOC) is a fatal gynecologic malignancy in the U.S. with limited treatment options. New therapeutic strategies include targeting of the cell cycle checkpoints, e.g., ATR and CHK1. We recently reported a promising clinical activity of the CHK1 inhibitor (CHK1i) prexasertib monotherapy in BRCA wild-type (BRCAwt) HGSOC patients. In this study, biopsies of treated patients and cell line models were used to investigate possible mechanisms of resistance to CHK1i. We report that BRCAwt HGSOC develops resistance to prexasertib monotherapy via a prolonged G2 delay induced by lower CDK1/CyclinB1 activity, thus preventing cells from mitotic catastrophe and cell death. On the other hand, we noted CHK1's regulation on RAD51-mediated homologous recombination (HR) repair was not altered in CHK1i-resistant cells. Therefore, CHK1i sensitizes CHK1i-resistant cells to DNA damaging agents such as gemcitabine or hydroxyurea by inhibition of HR. In summary, our results demonstrate new mechanistic insights of functionally distinct CHK1 activities and highlight a potential combination treatment approach to overcome CHK1i resistance in BRCAwt HGSOC.

RAD6B is a major mediator of triple negative breast cancer cisplatin resistance: Regulation of translesion synthesis/Fanconi anemia crosstalk and BRCA1 independence

Triple negative breast cancer (TNBC) is an aggressive breast cancer subtype with few therapy options besides chemotherapy. Although platinum-based drugs have shown initial activity in BRCA1-mutated TNBCs, chemoresistance remains a challenge. Here we show that RAD6B (UBE2B), a principal mediator of translesion synthesis (TLS), is overexpressed in BRCA1 wild-type and mutant TNBCs, and RAD6B overexpression correlates with poor survival. Pretreatment with a RAD6-selective inhibitor, SMI#9, enhanced cisplatin chemosensitivity of BRCA1 wild-type and mutant TNBCs. SMI#9 attenuated cisplatin-induced PCNA monoubiquitination (TLS marker), FANCD2 (Fanconi anemia (FA) activation marker), and TLS polymerase POL η. SMI#9-induced decreases in γH2AX levels were associated with concomitant inhibition of H2AX monoubiquitination, suggesting a key role for RAD6 in modulating cisplatin-induced γH2AX via H2AX monoubiquitination. Concordantly, SMI#9 inhibited γH2AX, POL η and FANCD2 foci formation. RAD51 foci formation was unaffected by SMI#9, however, its recruitment to double-strand breaks was inhibited. Using the DR-GFP-based assay, we showed that RAD6B silencing or SMI#9 treatment impairs homologous recombination (HR) in HR-proficient cells. DNA fiber assays confirmed that restart of cisplatin-stalled replicating forks is inhibited by SMI#9 in both BRCA1 wild-type and mutant TNBC cells. Consistent with the in vitro data, SMI#9 and cisplatin combination treatment inhibited BRCA1 wild-type and mutant TNBC growth as compared to controls. These RAD6B activities are unaffected by BRCA1 status of TNBCs suggesting that the RAD6B function in TLS/FA crosstalk could occur in HR-dependent and independent modes. Collectively, these data implicate RAD6 as an important therapeutic target for TNBCs irrespective of their BRCA1 status.

Nano-delivery of RAD6/Translesion Synthesis Inhibitor SMI#9 for Triple-negative Breast Cancer Therapy

The triple-negative breast cancer (TNBC) subtype, regardless of their BRCA1 status, has the poorest outcome compared with other breast cancer subtypes, and currently there are no approved targeted therapies for TNBC. We have previously demonstrated the importance of RAD6-mediated translesion synthesis pathway in TNBC development/progression and chemoresistance, and the potential therapeutic benefit of targeting RAD6 with a RAD6-selective small-molecule inhibitor, SMI#9. To overcome SMI#9 solubility limitations, we recently developed a gold nanoparticle (GNP)-based platform for conjugation and intracellular release of SMI#9, and demonstrated its in vitro cytotoxic activity toward TNBC cells. Here, we characterized the in vivo pharmacokinetic and therapeutic properties of PEGylated GNP-conjugated SMI#9 in BRCA1 wild-type and BRCA1-mutant TNBC xenograft models, and investigated the impact of RAD6 inhibition on TNBC metabolism by ¹H-NMR spectroscopy. GNP conjugation allowed the released SMI#9 to achieve higher systemic exposure and longer retention as compared with the unconjugated drug. Systemically administered SMI#9-GNP inhibited the TNBC growth as effectively as intratumorally injected unconjugated SMI#9. Inductively coupled mass spectrometry analysis showed highest GNP concentrations in tumors and liver of SMI#9-GNP and blank-GNP-treated mice; however, tumor growth inhibition occurred only in the SMI#9-GNP-treated group. SMI#9-GNP was tolerated without overt signs of toxicity. SMI#9-induced sensitization was associated with perturbation of a common set of glycolytic pathways in BRCA1 wild-type and BRCA1-mutant TNBC cells. These data reveal novel SMI#9 sensitive markers of metabolic vulnerability for TNBC management and suggest that nanotherapy-mediated RAD6 inhibition offers a promising strategy for TNBC treatment.

Restored replication fork stabilization, a mechanism of PARP inhibitor resistance, can be overcome by cell cycle checkpoint inhibition

Poly(ADP-ribose) polymerase (PARP) inhibition serves as a potent therapeutic option eliciting synthetic lethality in cancers harboring homologous recombination (HR) repair defects, such as BRCA mutations. However, the development of resistance to PARP inhibitors (PARPis) poses a clinical challenge. Restoration of HR competency is one of the many molecular factors contributing to PARPi resistance. Combination therapy with cell cycle checkpoint (ATR, CHK1, and WEE1) inhibitors is being investigated clinically in many cancers, particularly in ovarian cancer, to enhance the efficacy and circumvent resistance to PARPis. Ideally, inhibition of ATR, CHK1 and WEE1 proteins will abrogate G2 arrest and subsequent DNA repair via restored HR in PARPi-treated cells. Replication fork stabilization has recently been identified as a potential compensatory PARPi resistance mechanism, found in the absence of restored HR. ATR, CHK1, and WEE1 each possess different roles in replication fork stabilization, providing different mechanisms to consider when developing combination therapies to avoid continued development of drug resistance. This review examines the impact of ATR, CHK1, and WEE1 on replication fork stabilization. We also address the therapeutic potential for combining PARPis with cell cycle inhibitors and the possible consequence of combination therapies which do not adequately address both restored HR and replication fork stabilization as PARPi resistance mechanisms.

Pharmacological targeting of RAD6 enzyme-mediated translesion synthesis overcomes resistance to platinum-based drugs

Platinum drug-induced cross-link repair requires the concerted activities of translesion synthesis (TLS), Fanconi anemia (FA), and homologous recombination repair pathways. The E2 ubiquitin-conjugating enzyme RAD6 is essential for TLS. Here, we show that RAD6 plays a universal role in platinum-based drug tolerance. Using a novel RAD6-selective small-molecule inhibitor (SMI#9) targeting the RAD6 catalytic site, we demonstrate that SMI#9 potentiates the sensitivities of cancer cells with innate or acquired cisplatin or oxaliplatin resistance. 5-Iododeoxyuridine/5-chlorodeoxyuridine pulse-labeling experiments showed that RAD6 is necessary for overcoming cisplatin-induced replication fork stalling, as replication-restart was impaired in both SMI#9-pretreated and RAD6B-silenced cells. Consistent with the role of RAD6/TLS in late-S phase, SMI#9-induced DNA replication inhibition occurred preferentially in mid/late-S phase. The compromised DNA repair and chemosensitization induced by SMI#9 or RAD6B depletion were associated with decreased platinum drug-induced proliferating cell nuclear antigen (PCNA) and FANCD2 monoubiquitinations (surrogate markers of TLS and FA pathway activation, respectively) and with attenuated FANCD2, RAD6, γH2AX, and POL η foci formation and cisplatin-adduct removal. SMI#9 pretreatment synergistically increased cisplatin inhibition of MDA-MB-231 triple-negative breast cancer cell proliferation and tumor growth. Using an isogenic HCT116 colon cancer model of oxaliplatin resistance, we further show that γH2AX and monoubiquitinated PCNA and FANCD2 are constitutively up-regulated in oxaliplatin-resistant HCT116 (HCT116-OxR) cells and that γH2AX, PCNA, and FANCD2 monoubiquitinations are induced by oxaliplatin in parental HCT116 cells. SMI#9 pretreatment sensitized HCT116-OxR cells to oxaliplatin. These data deepen insights into the vital role of RAD6/TLS in platinum drug tolerance and reveal clinical benefits of targeting RAD6 with SMI#9 for managing chemoresistant cancers.

Abstract 3786: Rad6 inhibition enhances paclitaxel sensitivity of triple negative breast cancer cells by inducing mitotic spindle defects

Triple negative breast cancers (TNBC) lack estrogen receptors, and progesterone receptors, and HER2/neu receptor amplifications, making targeted therapies unsuitable. The taxane based drug paclitaxel (PTX) is used as a first line chemotherapy. PTX is a microtubule stabilizer that induces G2/M arrest and mitotic catastrophe. Loss of BRCA1 often seen in TNBC patients is associated with PTX resistance. Rad6 is an E2 ubiquitin conjugating enzyme that has two human homologues, Rad6A (UBE2A) and Rad6B (UBE2B), and high Rad6B expression rather than Rad6A is associated with poor survival of TNBC patients. Rad6 is associated with centrosomes at all phases of the cell cycle, and constitutive overexpression of Rad6B in nontransformed MCF10A breast cells leads to centrosome amplification and aneuploidy. Inhibition of Rad6 enzymatic activity, with our novel Rad6-selective small molecule inhibitor (SMI#9) induces G2/M arrest, much like PTX. We hypothesize that the overexpression of Rad6B commonly found in BRCA1 wt and BRCA1 mut TNBCs contributes to taxane resistance by promoting centrosome amplification and enhancing microtubule dynamics. Thus, targeting Rad6 will confer taxane sensitivity by preventing centrosome reduplication and/or microtubule hypernucleation, strengthening G2/M arrest, and ensuring terminal mitotic catastrophe. Immunostaining shows Rad6 is overexpressed in BRCA1 wt and BRCA1 mut breast cancer tissues and TNBC cell lines. Immunostaining of the centrosomal protein pericentrin shows centrosome amplification in both BRCA1 wt and BRCA1 mut TNBC cells. MTT data show SMI#9 synergistically sensitizes both BRCA1 wt (MDA-MB-468) and BRCA1 mut (HCC1937) TNBC cell lines to PTX. Colony forming assays corroborate these data and show that addition of SMI#9 diminishes colony forming efficiency of PTX pretreated MDA-MB-468 cells. SMI#9 treatment of HCC1937 PTX resistant colonies results in increases in cells with enlarged and multiple nuclei (characteristic of mitotic catastrophe). Western blot analysis of Tau, a marker of PTX sensitivity, indicates PTX, SMI#9, and PTX+SMI#9 treatments decrease the steady state levels of the 1N3R and 0N4R, or 1N3R Tau isoforms in MDA-MB-468 and HCC1937 cells, respectively. Analysis of cyclin B1, a marker of G2/M arrest, shows increases in cyclin B1 levels in PTX, SMI#9, and PTX+SMI#9 treated MDA-MB-468 cells, whereas cyclin B1 is degraded in HCC1937 cells treated with these agents (indicative of mitotic catastrophe). Immunofluorescence staining shows that Tau localization to the mitotic spindles is unaffected by PTX, SMI#9, or PTX+SMI#9. However, treatments including SMI#9 resulted in mitotic cells with defective or monopolar mitotic spindles. These data implicate a role for Rad6 in centrosome duplication/separation and provide mechanistic support for inhibiting Rad6 to enhance PTX sensitivity. Supported by NCI R21 CA178117 and T32-CA009531.

Citation Format: Brittany Haynes, Kristen Cunningham, Malathy Shekhar. Rad6 inhibition enhances paclitaxel sensitivity of triple negative breast cancer cells by inducing mitotic spindle defects. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3786.

Abstract P3-14-06: Evaluation of the therapeutic efficacy of a Rad6 small molecule inhibitor in triple negative breast cancer cells

Triple negative breast cancers (TNBCs) lack estrogen and progesterone receptors and Her2/neu amplification, and are hence not treatable with therapies targeting these molecules. TNBCs have upregulated DNA damage response mechanisms, including the Rad6 postreplication repair (PRR) pathway, that potentially contribute to chemoresistance. Rad6 is a major component of the PRR pathway and its ubiquitin conjugating (UBC) activity is critical for its function. Rad6 expression is low in normal breast cells and tissues but the Rad6 homolog Rad6B is overexpressed in invasive, metastatic and chemoresistant BrCas. Constitutive overexpression of Rad6B in MCF10A cells induces resistance to cisplatin and doxorubicin. TCGA analysis of TNBC patient data showed an association between high Rad6B expression (but not Rad6A) and decreased overall survival. We recently reported the development of a novel Rad6-selective small molecule inhibitor (SMI#9) that inhibits Rad6 UBC activity, migration, and induces apoptosis in TNBC cells but has no effect on MCF10A cells. Since SMI#9 has limited aqueous solubility, in this study we synthesized a modified analog of SMI#9 to enable conjugation via a hydrolyzable ester bond to gold nanoparticle (GNP) and to improve delivery. GNP tethered SMI#9 (SMI#9-GNP) was characterized for purity, ligand conjugation and size by thermogravimetric analysis, atomic force microscopy, transmission electron microscopy, UV-Vis spectroscopy and zeta sizer, and for cellular uptake and drug release by FTIR and mass spectrometry. We compared the activities of SMI#9-GNP and free SMI#9 for cytotoxicity and intracellular localization in mesenchymal (MDA-MB-231 and SUM1315) and basal (MDA-MB-468 and HCC1937) subtypes of TNBC, and in MCF10A cells. Whereas free SMI#9 was cytotoxic to all TNBC cells, SMI#9-GNP demonstrated as good or better cytotoxicity than free SMI#9 only in mesenchymal TNBC cells. MCF10A cells were unaffected by both free and SMI#9-GNP. Consistent with cellular sensitivities, SMI#9-GNP is efficiently endocytosed and processed in lysosomes in mesenchymal TNBC cells, while uptake into basal TNBC cells is compromised by cell microenvironment induced SMI#9-GNP aggregation. SMI#9-GNP treatment induces mitochondrial dysfunction, and stabilization and hyperactivation of PARP-1 that was commensurate with autophagy (indicated by LC3-I to LC3-II conversion). Rad6 loss and PARP-1 hyperactivation are associated with mitochondrial dysfunction, and since inhibition of Rad6 induces both mitochondrial dysfunction and PARP-1 activation this implicates a potential novel role for Rad6 in linking these processes. In summary, our data show that SMI#9-GNP is a suitable delivery vehicle and that the SMI#9 released from GNP conjugate functions similarly as free SMI#9. Our data also illustrate how cell microenvironment induced changes in the physical properties of GNP-drug conjugates can have important implications in the application of nanoparticles in cancer therapy. Supported by NIH R21 CA178117.

Citation Format: Haynes B, Zhang Y, Li J, Petit S, Westwell A, Mao G, Shekhar M. Evaluation of the therapeutic efficacy of a Rad6 small molecule inhibitor in triple negative breast cancer cells. [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 P3-14-06.

Abstract 835: COPD and risk of lung cancer in post-menopausal women: findings from the Women's Health Initiative

Background: Lung cancer and chronic obstructive pulmonary disease (COPD) are leading causes of morbidity and mortality in the United States. Cigarette smoking is associated with both lung cancer and COPD, but whether COPD independently predicts lung cancer risk is debated. To examine this question in a large, prospective study, we constructed risk models using data from the observational study arm of the Women's Health Initiative.

Methods: Initial analyses included 89,384 women (n = 1,479 lung cancers) with complete baseline information on cigarette smoking and COPD status. We created a second, time-varying model to account for incident smoking that occurred during the eight year follow up period, in addition to the number of pack years reported at baseline. Estimates from Cox proportional hazard models were used to assess the association between COPD and lung cancer. The baseline hazard was stratified by age at study entry in all models. COPD status was self-reported, and diagnoses within one year of lung cancer diagnoses were not included. Reported lung cancers were adjudicated via medical record.

Results: There was an interaction between number of pack years (continuous) of smoking at baseline and COPD status (p<0.001). Never smokers with COPD were 2.7 times more likely to develop lung cancer compared to never smokers without COPD, after adjusting for race, education, income and body mass index (HR = 2.70, 95% CI: 2.12, 3.45). Similar risk of lung cancer associated with COPD was seen among smokers with 20 pack years of smoking (HR = 2.37, 95% CI: 1.96, 2.87) and at 40 pack years of smoking (HR = 2.08, 95% CI: 1.77, 2.45) after adjustment. From the time-varying models, women with COPD had approximately 2 times the risk of developing lung cancer compared to those who did not, after adjusting for smoking, race, education, income and body mass index (HR = 1.90, 95% CI: 1.54, 2.34). COPD was associated with all subtypes of lung cancer after adjustment for smoking, with hazard ratios ranging from 1.59-2.15 for different histological subtypes of non-small cell lung cancers. Smokers with COPD were 4.6 times more likely to develop small cell lung cancers compared to those without COPD (HR = 4.68, 95% CI: 2.67, 8.20).

Conclusion: These data suggest that COPD is an independent risk factor for the development of lung cancer, and should be considered when constructing risk models.

Citation Format: Michele L. Cote, Amy Lehman, Rowen Chlebowski, Brittany Haynes, Gloria Ho, Manali Patel, Lori Sakoda, Michael Simon, Heather Wakelee, Ann Schwartz. COPD and risk of lung cancer in post-menopausal women: findings from the Women's Health Initiative. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 835. doi:10.1158/1538-7445.AM2015-835

Abstract 1662: Therapeutic relevance of the Rad6/translesion synthesis pathway in BRCA1-related triple-negative breast cancer cells

Triple negative breast cancers (TNBCs) comprise ∼15-20% of all breast cancers (BrCas), and their treatment is challenging because they are not treatable with ER, PgR or Her2/neu-targeted therapies. Since TNBCs and BRCA-mutated BrCas share many histopathologic features including aberrant DNA repair pathways, the concept of targeting DNA repair defects with agents such as platinum (Pt) compounds is applied for treatment of TNBC patients. Pt drugs induce DNA replication stalling interstrand DNA crosslinks (ICLs), the repair of which require concerted activities of nucleotide excision repair, Fanconi anemia (FA)/BRCA homologous recombination repair (HRR) and translesion synthesis (TLS) pathways. The therapeutic efficacies of these drugs are often limited by the cancer cell's enhanced ability to repair/tolerate these toxic DNA lesions. The TLS pathway a.k.a DNA damage tolerance pathway is critical for cell survival in the face of DNA damage. TLS is a crucial initial step in ICL repair as it synthesizes DNA across the lesion thus preparing the damaged DNA template for repair by the FA network and HR pathway, processes critical for ICL repair. The Rad6 gene is a principal component of the TLS pathway and previous work in our lab has shown its important role in BrCa development/progression and acquisition of cisplatin (CDDP) resistance. To understand the involvements of Rad6/TLS and FA/BRCA in CDDP-induced DNA damage repair, we evaluated CDDP sensitivities, CDDP-induced DNA damage responses and stalled replication restarts in wt-BRCA1 (MDA-MB-231, MDA-MB-468) and mut-BRCA1 (HCC1937, SUM1315) TNBCs. Data from MTT assays showed no correlation between CDDP sensitivity and BRCA1 status; however, pretreatment with our recently developed Rad6 small molecule inhibitor (SMI) enhanced CDDP sensitivity of all TNBC cell lines regardless of their BRCA1 status. Consistent with these data, immunoblot analysis showed that treatment with the Rad6 SMI attenuated the CDDP-induced PCNA ubiquitinations (a hall mark of Rad6/TLS activity), as well as the steady-state levels of FancD2 (a surrogate marker of FA pathway activation), pol eta (TLS polymerase), and Rad51 (critical for HRR) in both wt-BRCA1 and mut-BRCA1 TNBC cells. IdU/CldU labeling assays showed that Rad6 inhibition mitigated the restart of CDDP-induced stalled replication forks. Whereas Rad6 is expressed weakly in normal breast tissues and overexpressed in BrCas, immunohistochemical analysis showed strong nuclear staining for Rad6 in the normal ducts of mut-BRCA1 clinical breast tissues implicating an important role for Rad6 in mut-BRCA1 BrCas. Our data suggest an important role for the Rad6/TLS pathway in processing Pt-induced ICLs in both wt-BRCA1 and mut-BRCA1 TNBCs and the potential therapeutic value of inhibiting this pathway in TNBCs. Supported by NIH CA178117-01.

Note: This abstract was not presented at the meeting.

Citation Format: Brittany Haynes, Hend Kothayer, Andrew Westwell, Malathy Shekhar. Therapeutic relevance of the Rad6/translesion synthesis pathway in BRCA1-related triple-negative breast cancer cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1662. doi:10.1158/1538-7445.AM2015-1662

Crosstalk between translesion synthesis, Fanconi anemia network, and homologous recombination repair pathways in interstrand DNA crosslink repair and development of chemoresistance

Bifunctional alkylating and platinum based drugs are chemotherapeutic agents used to treat cancer. These agents induce DNA adducts via formation of intrastrand or interstrand (ICL) DNA crosslinks, and DNA lesions of the ICL type are particularly toxic as they block DNA replication and/or DNA transcription. However, the therapeutic efficacies of these drugs are frequently limited due to the cancer cell's enhanced ability to repair and tolerate these toxic DNA lesions. This ability to tolerate and survive the DNA damage is accomplished by a set of specialized low fidelity DNA polymerases called translesion synthesis (TLS) polymerases since high fidelity DNA polymerases are unable to replicate the damaged DNA template. TLS is a crucial initial step in ICL repair as it synthesizes DNA across the lesion thus preparing the damaged DNA template for repair by the homologous recombination (HR) pathway and Fanconi anemia (FA) network, processes critical for ICL repair. Here we review the molecular features and functional roles of TLS polymerases, discuss the collaborative interactions and cross-regulation of the TLS DNA damage tolerance pathway, the FA network and the BRCA-dependent HRR pathway, and the impact of TLS hyperactivation on development of chemoresistance. Finally, since TLS hyperactivation results from overexpression of Rad6/Rad18 ubiquitinating enzymes (fundamental components of the TLS pathway), increased PCNA ubiquitination, and/or increased recruitment of TLS polymerases, the potential benefits of selectively targeting critical components of the TLS pathway for enhancing anti-cancer therapeutic efficacy and curtailing chemotherapy-induced mutagenesis are also discussed.

Abstract 820: Inhibition of Rad6 sensitizes triple negative breast cancer cells to platinum-based therapy

Treatment of triple negative breast cancers (TNBCs) poses a clinical challenge because they are not treatable with therapies targeting estrogen receptor and Her2/neu as they lack expression of estrogen, progesterone, and Her2/neu receptors. Since TNBCs share several histologic features with BRCA1-related breast cancer, and these breast cancers have aberrant DNA repair, DNA repair pathways are thought to play a role in TNBC development and drug response. Platinum (Pt)-based compounds induce toxic interstrand DNA crosslinks (ICL), the repair of which requires activities of BRCA/Fanconi anemia (FA) network and Rad6 postreplication DNA repair (PRR) pathways. PRR pathway confers tolerance to DNA damage by enabling cells to complete DNA replication in the face of damage and avoid mitotic catastrophe. Rad6 regulates PCNA ubiquitination, a critical event for PRR, and also promotes FancD2 ubiquitination, a critical event for ICL repair. We have recently reported the identification and synthesis of a small molecule inhibitor (SMI) of Rad6 that targets its ubiquitin conjugating activity. We hypothesize that targeting Rad6 will be beneficial to TNBCs treated with Pt-based compounds by preventing acquisition of resistance and overcoming Pt resistance. Treatment with the Rad6 SMI enhanced CDDP sensitivity of BRCA1 wild type MDA-MB-231 TNBC cells that have intrinsic CDDP resistance. Western blot analysis showed that the CDDP-induced DNA damage is accompanied by PCNA and FancD2 monoubiquitination (surrogate markers of Rad6 and FA pathway activation, respectively) and increases in ΓH2AX levels. Treatment of MDA-MB-231 cells with the Rad6 SMI attenuated CDDP-induced PCNA and FancD2 ubiquitination, and ΓH2AX levels. Treatment with Rad6 SMI inhibited formation of CDDP-induced Rad6, PCNA, FancD2, translesion synthesis polymerase eta and ΓH2AX nuclear foci. These data suggest that Rad6 plays an important role in recruitment of repair factors during CDDP-induced DNA damage response. To verify these findings, IdU/CldU double labeling assays were performed to evaluate the impact of Rad6 inhibition on restart of CDDP-induced stalled replication forks. Whereas restarting of CDDP-induced stalled replication forks occurred efficiently in MDA-MB-231 cells treated with nontarget siRNA or vehicle, resumption of stalled forks was severely compromised in MDA-MB-231 cells treated with Rad6B siRNA or Rad6 SMI. Consistent with the in vitro data, orthotopic implantation of MDA-MB-231 cells pretreated with Rad6 SMI or CDDP alone produced significantly smaller tumors compared to vehicle, and tumor growth was further mitigated when cells were pretreated with both CDDP and Rad6 SMI. These data imply a critical role for the Rad6 PRR pathway in repair of Pt-induced DNA damage and that inhibition of Rad6 catalytic activity may be exploited to sensitize TNBCs to Pt therapies. Supported by NIH 1R21CA178117-01.

Citation Format: Brittany Haynes, Matthew Sanders, Malathy Shekhar. Inhibition of Rad6 sensitizes triple negative breast cancer cells to platinum-based therapy. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 820. doi:10.1158/1538-7445.AM2014-820

Rad6 is a Potential Early Marker of Melanoma Development

Melanoma is the leading cause of death from skin cancer in industrialized countries. Several melanoma-related biomarkers and signaling pathways have been identified; however, their relevance to melanoma development/progression or to clinical outcome remains to be established. Aberrant activation of Wnt/β-catenin pathway is implicated in various cancers including melanoma. We have previously demonstrated Rad6, an ubiquitin-conjugating enzyme, as an important mediator of β-catenin stability in breast cancer cells. Similar to breast cancer, β-catenin-activating mutations are rare in melanomas, and since β-catenin signaling is implicated in melanoma, we examined the relationship between β-catenin levels/activity and expression of β-catenin transcriptional targets Rad6 and microphthalmia-associated transcription factor-M (Mitf-M) in melanoma cell models, and expression of Rad6, β-catenin, and Melan-A in nevi and cutaneous melanoma tissue specimens. Our data show that Rad6 is only weakly expressed in normal human melanocytes but is overexpressed in melanoma lines. Unlike Mitf-M, Rad6 overexpression in melanoma lines is positively associated with high molecular weight β-catenin protein levels and β-catenin transcriptional activity. Double-immunofluorescence staining of Rad6 and Melan-A in melanoma tissue microarray showed that histological diagnosis of melanoma is significantly associated with Rad6/Melan-A dual positivity in the melanoma group compared to the nevi group (P=.0029). In contrast to strong β-catenin expression in normal and tumor areas of superficial spreading malignant melanoma (SSMM), Rad6 expression is undetectable in normal areas and Rad6 expression increases coincide with increased Melan-A in the transformed regions of SSMM. These data suggest a role for Rad6 in melanoma pathogenesis and that Rad6 expression status may serve as an early marker for melanoma development.

Abstract P3-08-04: Impact of CYP3A variation on estrone levels and breast cancer risk

Background: Epidemiological studies provide strong evidence for a role of endogenous sex steroids in the etiology of breast cancer. Our aim was to identify common variants in genes involved in sex steroid synthesis or metabolism that were associated with premenopausal hormone levels and breast cancer risk.

Methods: We measured urinary estrone glucuronide (E1G) and pregnanediol glucuronide (PG) using a protocol specifically developed to account for cyclic variation in hormone levels during the menstrual cycle, plasma sex hormone-binding globulin (SHBG) and androgenic precursors in up to 763 healthy premenopausal women. We genotyped 642 single nucleotide polymorphisms (SNPs) in these women; a single SNP was further tested for association with breast cancer risk in data from 10,551 breast cancer case patients and 17,535 control subjects. All statistical tests were two-sided.

Results: rs10273424 mapping approximately 50kb centromeric to the cytochrome P450 3A (CYP3A) cluster (7q22.1) was associated with a 21.8% reduction in E1G levels (P = 2.7 × 10−9) and a modest reduction in breast cancer risk in cases diagnosed at or before age 50 (OR = 0.91; P = 0.03) but not older cases (odds ratio (OR) = 1.01; P = 0.82). A rare non-synonymous SHBG SNP was associated with reduced plasma SHBG levels.

Conclusions: Genetic variation in non-coding sequences flanking the CYP3A locus contributes to variance in premenopausal E1G levels and breast cancer risk in younger cases. Since CYP3A4, the most predominantly expressed CYP3A gene, is responsible for metabolism of endogenous and exogenous hormones and hormonal agents such as tamoxifen, used in the treatment of breast cancer this association may have wider implications.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-08-04.

Abstract PD07-07: Prediction of antiproliferative response to lapatinib by HER3 in an exploratory analysis of HER2-non-amplified (HER2−) breast cancer in the MAPLE presurgical study (CRUK E/06/039)

Aim: To identify pretreatment biomarker predictors of Ki67 response to lapatinib in women with HER2− primary breast cancer.

Background: Lapatinib is an EGFR/HER2 inhibitor. Its clinical use is restricted to HER2 overexpressing disease. The MAPLE (Molecular Antiproliferative Predictors of Lapatinib's Effects) presurgical window of opportunity study of lapatinib vs placebo was conducted in women with HER2-amplified (HER2+) or HER2− primary disease. Ki67 (primary end-point) was reduced by a geomean 46% (95%CI 23–63%, p = 0.002) and 27% (95%CI 8–42%, p = 0.008) in HER2+ and HER2− disease, respectively (Leary et al, AACR 2012). We have now assessed whether predictive biomarkers of the antiproliferative response in HER2− disease could be identified.

Methods: 121 primary breast cancer patients were randomized (3:1) to 14 days of 1500mg/d lapatinib or placebo before surgery. Biopsies were taken before treatment and at surgery. Ki67 responders were defined as having a >/=50% reduction in Ki67 compared to baseline (Ellis, P et al, Breast Cancer Res Treat 1998, 48, 107). ER, PgR, HER2, EGFR, pAKT, pERK1/2 (nuclear and cytoplasmic), stathmin and apoptosis (TUNEL) were assessed by IHC (+FISH for HER2[all cases]) and scored visually by continuous methods. HER2, HER3, epiregulin (epir), amphiregulin (amphir) and neuregulin (neur) were assessed by qrtPCR.

Results: Three of the 121 patients were excluded because of inadequate biopsy material. Ninety-one of the remaining 118 patients received lapatinib: 7/19 (37%) HER2+ cases and 10/72 (14%) HER2− cases were Ki67 responders. Thus while the proportion of Ki67 responders was higher for HER2+ disease there was a similar or higher absolute number of responders with HER2− disease. All of the following relates to patients with HER2− disease. None of the pretreatment levels of ER, PgR, pAKT, pERK1/2, EGFR, epir, amphir or neur were associated with Ki67 response (p > 0.20). However, HER3 (p = 0.01) and HER2 (p = 0.06) mRNA levels were associated with greater Ki67 response. There was a tendency for Ki67 response to be greater with lower baseline Ki67 (p = 0.07). Multivariate analysis showed only HER3 mRNA levels to be independently significant. HER2 and HER3 mRNA levels were highly correlated (rho = 0.67, p < 0.001), a relationship confirmed in 2 other datasets (Wang et al, Breast Cancer Res, 2011, 13, R92; Dunbier et al, submitted). All Ki67 responders were above the median for both HER3 and HER2 expression.

Conclusions: Lapatinib is antiproliferative in a subgroup of HER2− tumours. This exploratory analysis indicates that they are characterized by high HER3 expression. The possible importance of high HER2:HER3 heterodimers in predicting this response is supported by the relationship between HER2 and HER3 expression. Further exploration of lapatinib is merited in HER2− cases with high HER3 expression.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD07-07.

Use of membrane collectors in electrostatic precipitators

Membrane collection surfaces, developed and patented by researchers at Ohio University, were used to replace steel plates in a dry electrostatic precipitator (ESP). Such replacement facilitates tension-based rapping, which shears the adhered particle layer from the collector surface more effectively than hammer-based rapping. Tests were performed to measure the collection efficiency of the membranes and to quantify the potential improvements of this novel cleaning technique with respect to re-entrainment. Results indicate that even semiconductor materials (e.g., carbon fibers) collect ash nearly as efficiently as steel plates, potentially indicating that collection surface resistivity is primarily dictated by the accumulated ash layer and not by the underlying plate conductivity. In addition, virtually all sheared particles separated from the collecting membranes fell within the boundary layer of the membrane, indicating extremely low potential for re-entrainment.

Effect of thymectomy on human peripheral blood T cell pools in myasthenia gravis

The human thymus is required for establishment of the T cell pool in fetal life, but postnatal thymectomy does not lead to immunodeficiency in humans. Because thymectomy in humans is performed for treatment of myasthenia gravis (MG), we have studied patients with MG for effects of thymectomy on peripheral blood (PB) naive (CD45RA(+), CD62L(+)) and memory (CD45RO(+)) T cells. We have also determined the effect of thymectomy on levels of PB cells containing signal joint TCR delta excision circles (TRECs), a molecular marker of thymus emigrants that have divided few times after leaving the thymus. In 17 nonthymectomized and 26 thymectomized MG patients studied at varying times after thymectomy (1 day to 41 years), we found no significant mean difference in PB T cell TREC levels between ages 40 and 80 years. However, both thymectomized and nonthymectomized MG patients had lower PB T cell TREC levels than did age-matched normal subjects (p < 0.0001 for both). These data demonstrated that MG itself or treatment for MG decreased thymopoiesis independent of thymectomy. Next, to control for disease activity and treatment, we prospectively studied 10 MG patients before and from 27 to 517 days after thymectomy. We found that thymectomy decreased CD4 or CD8 T cell TREC concentrations most when thymopoiesis was active before thymectomy (six of six patients), but had little effect in patients when thymopoiesis was minimal (four of four patients). In contrast, there was no significant effect of thymectomy on absolute numbers of naive PB T cells. Thus, in MG, removal of a thymus with active thymopoiesis resulted in a significant fall in PB TREC(+) T cells postthymectomy.

Intraocular penetration of tamoxifen

OBJECTIVE

To document ocular penetration of oral tamoxifen in patients being administered systemic therapy by measuring intraocular and serum levels of the drug in a series of patients undergoing elective ocular surgery.

DESIGN

Nonrandomized, prospective, comparative trial.

PARTICIPANTS

Twenty-one eyes of 21 patients undergoing elective ocular surgery (cataract extraction or vitrectomy). Twenty patients were using the antiestrogen, tamoxifen, and one participant was not. Nine patients were excluded in the final analysis because of inadequate sample size.

INTERVENTION

Preoperative serum samples and perioperative aqueous samples, vitreous samples, or both were obtained for each patient, and these were analyzed for tamoxifen and its metabolites. Dilated fundus examination was performed before surgery on all patients.

MAIN OUTCOME MEASURES

Evidence of tamoxifen, its metabolites, or both in the samples.

RESULTS

Tamoxifen was detected in all analyzed serum samples (range, 82.4-290.0 ng/ml.) from patients taking the medication and was found to have penetrated into both vitreous (range, 0.5-7.8 ng/ml) and aqueous (range, 0.5-3.9 ng/ml) cavities. No relationship was found between serum and intraocular levels.

CONCLUSIONS

This study shows that tamoxifen penetrates intraocular fluids to varying degrees. The drug levels in aqueous and vitreous do not appear to correlate with serum levels. Evidence of tamoxifen retinopathy or keratopathy was not seen.

The company they keep: the influence of peer relationships on adjustment to cystic fibrosis during adolescence

A grounded theory approach was used to explore the influence of peer relationships on adjustment to cystic fibrosis (CF) in 15 adolescents. Discovering the course was the core category that captured the influence of peers on adjustment to CF. Four subcategories were identified: (1) losing ground, (2) being out of the loop, (3) finding a new company of friends, (4) fighting a never-ending battle. The downward progression of CF and increasing social interactions with peers with CF during hospitalization helped them learn CF was a lifelong disease with relentless demands. Interventions should focus on strategies for promoting peer support, a positive attitude, and hope to create a sense of belonging, social competence, and well-being.

Hepatosplenic gamma-delta T-cell lymphoma as a late-onset posttransplant lymphoproliferative disorder in renal transplant recipients

We report 2 cases of renal transplant recipients in whom hepatosplenic gamma-delta T-cell lymphoma (gamma-delta HSTCL) developed 5 and 10 years after transplantation. Both patients had marked hepatosplenomegaly, B symptoms (weight loss, fever, and night sweats), and abnormal peripheral blood findings, including anemia in both, thrombocytopenia and leukoerythroblastic changes in 1, and leukocytosis in the other. Markedly atypical lymphoid infiltrate of intermediate to large cells was observed in the spleen, liver, and bone marrow. The malignant cells showed typical immunophenotype of gamma-delta T cells (CD2+, CD3+, CD4-, CD8-, CD7+, gamma-delta T-cell receptor-positive, and alpha-beta T-cell receptor-negative) with clonal T-cell receptor gene rearrangement and were of the V-delta-1 subset. In addition, the cells contained a cytolytic granule-associated protein, TIA-1, and Fas ligand, indicating cytotoxic T-cell differentiation. The malignant T cells in both cases were of host tissue origin. Both cases were negative for Epstein-Barr virus genome using Southern blot analysis. The patients did not respond to reduction of immunosuppression. Despite initial response to chemotherapy, both patients died within 6 months of diagnosis. Our findings indicate that gamma-delta HSTCL can occur as a late complication in transplant recipients.

Clinical pharmacology of selective estrogen receptor modulators

Observations of the pharmacology of tamoxifen and related compounds have lead to the concept of selective estrogen receptor modulators (SERMs). This new class of drug displays estrogen agonist or antagonist effects in a tissue-dependent manner and appears to offer an alternative to hormone replacement therapy for the prevention and treatment of osteoporosis and cardiovascular disease in postmenopausal women. Moreover, the estrogen antagonist actions of SERMs on breast tissue may also provide a protective effect against breast cancer. Although tamoxifen therapy reduces plasma cholesterol levels and maintains bone density, it is also associated with an increased risk of endometrial cancer, pulmonary embolism and deep vein thrombosis. This has lead to the development of newer SERMs which will hopefully lack these adverse effects of tamoxifen. These compounds promise a new era of disease prevention in the aging woman and their therapeutic potential is currently being evaluated in large-scale clinical trials.

Comparison of performance of interns completing the old (1993) and new interactive (1997) Advanced Trauma Life Support courses

BACKGROUND

The 1997 edition of the Advanced Trauma Life Support (ATLS) course emphasized interactivity as its major change. The impact of this change is assessed in this study.

METHODS

We compared two matched groups of 16 interns completing either the old (group I) or new (group II) ATLS course. Cognitive skills (40 standard ATLS questions plus 10 additional questions on airway and shock) and clinical trauma management skills (four trauma objective structured clinical examinations [OSCEs] on simulated trauma patients) were tested. OSCE station scores (standardized to a maximum of 20), priority scores (graded 1-7), organized approach global passing grades (graded 1-5), and initial assessment test station scores (graded 1-5) were compared.

RESULTS

Using ATLS criteria, three interns failed in each group. Post-ATLS examination question scores were similar (84.5+/-6.9 for group I, 85.9+/-7.1 for group II); scores for the airway and shock questions were higher but not different between the two groups. The four OSCE station mean scores varied between 13.9+/-2.0 and 15.4+/-2.1 for group I and were higher (p < 0.05) for group II (17.9+/-1.6 to 19.1+/-1.0). Priority scores were similar (group I, 6.3+/-1.1; group II, 6.4+/-1.2), but approach scores (3.9+/-0.1 for group I and 4.9+/-0.8 for group II) were lower in group I, as were the initial assessment test scores (2.9+/-0.2 for group I and 4.9+/-0.8 for group II). There were 8 honors grades in group I and 40 (p < 0.05) in group II. Interactive teaching, adult education principles, opportunities for discussion, provision of feedback, and stimulation of self-learning were rated more highly in the new course.

CONCLUSION

Using standard ATLS pass criteria, performance after the new and old ATLS courses was similar. Superior performances were measured using OSCE methodology for clinical trauma management skills after the new compared with the old ATLS course in this population of interns.

Effect of basic prehospital trauma life support program on cognitive and trauma management skills

We tested the effectiveness of a basic prehospital trauma life support (PHTLS) program by assessing cognitive performance and trauma management skills among prehospital trauma personnel. Fourteen subjects who completed a standard PHTLS course (group I) were compared to a matched group not completing a PHTLS program (group II). Cognitive performance was assessed on 50-item multiple choice examinations, and trauma skills management was assessed with four simulated trauma patients. Pre-PHTLS multiple choice questionnaire scores were similar (45.8 +/- 9.4% vs. 48.8 +/- 8.9% for groups I and II, respectively), but the post-PHTLS scores were higher in group I (80.4 +/- 5.9%) than in group II (52.6 +/- 4.9%). Pre-PHTLS simulated trauma patient performance scores (standardized to a maximum total of 20 for each station) were similar at all four stations for both groups, ranging from 7.9 to 10.4. The post-PHTLS scores were statistically significantly higher at all four stations for group I (range 16.0-19.0) compared to those for group II (range 8.0-11.1). The overall mean pre-PHTLS score for all four stations was 8.3 +/- 2.1 for group I and 8.8 +/- 2.0 (NS) for group II; the group I post-PHTLS mean score for the four stations was 17.1 +/- 2.7 (p < 0.05) compared to 9.1 +/- 2.3 for group II. Pre-PHTLS Adherence to Priority scores on a scale of 1 to 7 were similar (1.1 +/- 0.9 for group I and 1.2 +/- 1.0 for group II). Post-PHTLS group I Priority scores increased to 5.9 +/- 1.1. Group II (1.1 +/- 1.0) did not improve their post-PHTLS scores. The pre-PHTLS Organized Approach scores in the simulated trauma patients on a scale of 1 to 5 were 2.1 +/- 1.0 for group I and 1.9 +/- 1.2 for group II (NS) compared to 4.2 +/- 0.9 (p < 0.05) in group I and 2.0 +/- 0.8 in group II after PHTLS. This study demonstrates improved cognitive and trauma management skills performance among prehospital paramedical personnel who complete the basic PHTLS program.

Tirapazamine with cisplatin in patients with advanced non-small-cell lung cancer: a phase II study

PURPOSE

A phase II study was conducted to evaluate the safety and efficacy of tirapazamine combined with cisplatin for the treatment of patients with advanced non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Forty-four patients with stage IIIB/IV NSCLC were treated with a combination of tirapazamine and cisplatin. Patients received tirapazamine 260 mg/m2 administered intravenously over 2 hours, followed 1 hour later by cisplatin 75 mg/m2 administered over an additional hour, repeated every 21 days. The duration of therapy was meant to be limited to four cycles for nonresponders and eight cycles for responders.

RESULTS

Ten of 44 patients (23%) showed a partial response. The estimated median survival for all patients was 37 weeks. Toxicities were treatable and included grade 3 nausea or vomiting (25%), fatigue (27.3%), and muscle cramps (4.5%). No dose reductions were necessary.

CONCLUSION

The results show that tirapazamine can safely be added to cisplatin. Both the median survival and response rate observed strongly suggest that tirapazamine with cisplatin is more active than cisplatin alone.