DNA Repair Proteins as Molecular Targets for Cancer Therapeutics

Cancer therapeutics include an ever-increasing array of tools at the disposal of clinicians in their treatment of this disease. However, cancer is a tough opponent in this battle and current treatments which typically include radiotherapy, chemotherapy and surgery are not often enough to rid the patient of his or her cancer. Cancer cells can become resistant to the treatments directed at them and overcoming this drug resistance is an important research focus. Additionally, increasing discussion and research is centering on targeted and individualized therapy. While a number of approaches have undergone intensive and close scrutiny as potential approaches to treat and kill cancer (signaling pathways, multidrug resistance, cell cycle checkpoints, anti-angiogenesis, etc.), much less work has focused on blocking the ability of a cancer cell to recognize and repair the damaged DNA which primarily results from the front line cancer treatments; chemotherapy and radiation. More recent studies on a number of DNA repair targets have produced proof-of-concept results showing that selective targeting of these DNA repair enzymes has the potential to enhance and augment the currently used chemotherapeutic agents and radiation as well as overcoming drug resistance. Some of the targets identified result in the development of effective single-agent anti-tumor molecules. While it is inherently convoluted to think that inhibiting DNA repair processes would be a likely approach to kill cancer cells, careful identification of specific DNA repair proteins is increasingly appearing to be a viable approach in the cancer therapeutic cache

Experimenting with Cigarettes and Physical Activity Among Mexican Origin Youth: A Cross Sectional Analysis of the Interdependent Associations Among Sensation Seeking, Acculturation, and Gender

Sensation seeking tendencies tend to manifest during adolescence and are associated with both health-compromising behaviors and health-enhancing behaviors. The purpose of this study is to evaluate the relationship between sensation seeking and physical activity, a health-enhancing behavior, and between sensation seeking and experimenting with cigarettes, a health compromising-behavior, among a cohort of Mexican origin adolescents residing in the United States with different levels of acculturation. Methods: In 2009, 1,154 Mexican origin youth (50.5% girls, mean age 14.3 years (SD = 1.04)) provided data on smoking behavior, physical activity, linguistic acculturation, and sensation seeking. We conducted Pearson's chi(2) tests to examine the associations between categorical demographic characteristics (i.e. gender, age, country of birth and parental educational attainment) and both cigarette experimentation and physical activity and Student's t-tests to examine mean differences on the continuous variables (i.e. sensation seeking subscale) by the behaviors. We examined mean differences in the demographic characteristics, acculturation, and both behaviors for each of the sensation seeking subscales using analysis of variance (ANOVA). To examine relationships between the sensation seeking subscales, gender, and both behaviors, at different levels of acculturation we completed unconditional logistic regression analyses stratified by level of acculturation. Results: Overall, 23.3% had experimented with cigarettes and 29.0% reported being physically active for at least 60 minutes/day on at least 5 days/week. Experimenting with cigarettes and being physically active were more prevalent among boys than girls. Among girls, higher levels of sensation seeking tendencies were associated with higher levels of acculturation and experimentation with cigarettes, but not with physical activity. Among boys, higher levels of sensation seeking tendencies were associated with higher levels of acculturation, experimenting with cigarettes and being physically active. Conclusions: Our results suggest that interventions designed to prevent smoking among Mexican origin youth may need to address social aspects associated with acculturation, paying close attention to gendered manifestations of sensation seeking.National Cancer Institute CA105203, CA126988Caroline W. Law Fund for Cancer PreventionDan Duncan Family Institute for Cancer Prevention and Risk AssessmentCenter for Health Promotion and Disease Prevention Research in Underserved Population

Small-molecule inhibitors of proteins involved in base excision repair potentiate the anti-tumorigenic effect of existing chemotherapeutics and irradiation

There has been a recent upsurge in the development of small-molecule inhibitors specific to DNA repair proteins or proteins peripherally involved in base excision repair and the DNA damage response. These specific, nominally toxic inhibitors are able to potentiate the effect of existing cancer cell treatments in a wide array of cancers. One of the largest obstacles to overcome in the treatment of cancer is incomplete killing with initial cancer treatments, leading to resistant cancer. The progression of our understanding of cancer and normal cell responses to DNA damage has allowed us to develop biomarkers that we can use to help us predict responses of cancers, more specifically target cancer cells and overcome resistance. Initial successes using these small-molecule DNA repair inhibitors in target-validation experiments and in the early stages of clinical trials indicate an important role for these inhibitors, and allow for the possibility of a future in which cancers are potentially treated in a highly specific, individual manner

Targeting DNA repair pathways for cancer treatment: what's new?

Disruptions in DNA repair pathways predispose cells to accumulating DNA damage. A growing body of evidence indicates that tumors accumulate progressively more mutations in DNA repair proteins as cancers progress. DNA repair mechanisms greatly affect the response to cytotoxic treatments, so understanding those mechanisms and finding ways to turn dysregulated repair processes against themselves to induce tumor death is the goal of all DNA repair inhibition efforts. Inhibition may be direct or indirect. This burgeoning field of research is replete with promise and challenge, as more intricacies of each repair pathway are discovered. In an era of increasing concern about healthcare costs, use of DNA repair inhibitors can prove to be highly effective stewardship of R&D resources and patient expenses

Quantitative Immunohistochemistry Evaluating APE1 Expression in a Mouse Pancreatic Adenocarcinoma Model

poster abstractHigh levels of APE1 expression have been reported in numerous malignant tumors (brain, ovarian, pancreatic, and prostate). APE1 is an emerging target for a variety of novel anticancer drugs. Human apurinic endonuclease/redox factor 1 (APE1/Ref-1) mediates the repair of baseless sites in DNA caused by alkylation and oxidative DNA damage. Compound E3330 targets the redox signaling function of APE1. A pancreatic cancer mouse model was used to evaluate the drug effects of E3330 and Gemcitabine. The following doses were used across eight mice groups: E3330 at 12.5mg/kg, 25mg/kg, and 50mg/kg), Gemcitabine (35mg/kg), a combination of E3330 and Gemcitabine at 12.5mg/kg, 25mg/kg, and 50mg/kg), and an untreated vehicle control group. Mice were dosed i.p. 3 times weekly (MWF) and the study was completed at day 39. At termination, tumors were harvested and cross-sections were processed into a Paraffin block. Tissue sections were prepared and stained for H&E and an immunostain for CD31 (angiogenesis marker). Slides were imaged via Aperio whole slide digital system. The immunostains were evaluated to predict the effectiveness of treatment for pancreatic adenocarcinoma. IHC slides were quantitated using an Aperio positive pixel algorithm to determine the percent of angiogenesis in the various drug treatment groups. A biologically significant correlation was seen amongst the low and middle dose E3330 drug groups in comparison to the vehicle control. The (12.5 & 25) E3330 groups had an anti-angiogenic effect (shown by decreased CD31 positivity). These were slightly lower than the combinations of E3330 and Gemcitabine at the same dose treatment groups (possibly due to blunting of E3330). These results support previous studies demonstrating the antiangiogenic activity of E3330

QUANTITATIVE IMMUNOHISTOCHEMISTRY USING THE APERIO WHOLE SLIDE IMAGING SYSTEM EVALUATING ANGIOGENESIS AND HYPOXIA MARKERS IN PANCREATIC CARCINOMA MOUSE MODEL TREATED WITH VEHICLE CONTROL, E3330, AND A STAT 3 INHIBITOR

poster abstractInvestigation of the signaling pathways and molecular mechanisms that are major contributors to pancreatic tumor progression and its resistance to traditional therapies is lacking. Human apurinic endonuclease/redox factor 1 (APE/Ref-1) mediates repair of radiation-induced DNA lesions and regulates transcription via redox-based activation. Transcriptional factors HIF-1α, NFκB, and AP-1 are regulated by Ref-1 and are implicated in pancreatic tu-mor growth and the response to hypoxia. CD31 and CA IX (carbonic anhy-drase) were biomarkers used in an in vivo study to evaluate the effective-ness of E3330, an APE 1 inhibitor, in a pancreatic mouse model. Immunostained slides were scanned using the Aperio automated whole slide scanning system (Scanscope CS) and were viewed using ImageScopeTM. Single fields of view from each WSDI measuring ∼10,000,000 μm2 and rep-resenting the whole area of the tumor were selected for analysis using the Aperio positive pixel algorithm. The preclinical xenograft model evaluated human pancreatic carcinoma cell lines grown in NOD/SCID mice treated with the E3330 compound, a STAT 3 inhibitor, and an untreated vehicle control group. Immunohisto-chemistry (IHC) was used to predict effectiveness of treatment for pancreat-ic carcinoma based on CD31 and CA IX biomarker expression. IHC slides were quantified using both a traditional pathology hand count and the Aperio Imaging Analysis System. The positive pixel algorithm data closely mirrored the hand count for two biomarkers (CD31 and CA IX). In the E3330 treated group, the data showed CD31 (angiogenesis) was significantly knocked down with increased CA IX expression compared to the vehicle control. Hypoxia of the tumor cells was up in both treated groups. In summary, the Aperio im-aging analysis system matched the hand count pathology data. The drug ef-fects with E3330 exhibited both anti-angiogenesis and tumor hypoxia activi-ty in the tumors. This project was supported by the Center for Research and Learning’s Diversity Scholars Re-search Program

APE1/Ref-1 Role in Redox Signaling: Translational Applications of Targeting the Redox Function of the DNA Repair/Redox Protein APE1/Ref-1

The heterogeneity of most cancers diminishes the treatment effectiveness of many cancer-killing regimens. Thus, treatments that hold the most promise are ones that block multiple signaling pathways essential to cancer survival. One of the most promising proteins in that regard is APE1, whose reduction-oxidation activity influences multiple cancer survival mechanisms, including growth, proliferation, metastasis, angiogenesis, and stress responses. With the continued research using APE1 redox specific inhibitors alone or coupled with developing APE1 DNA repair inhibitors it will now be possible to further delineate the role of APE1 redox, repair and protein-protein interactions. Previously, use of siRNA or over expression approaches, while valuable, do not give a clear picture of the two major functions of APE1 since both techniques severely alter the cellular milieu. Additionally, use of the redox-specific APE1 inhibitor, APX3330, now makes it possible to study how inhibition of APE1’s redox signaling can affect multiple tumor pathways and can potentiate the effectiveness of existing cancer regimens. Because APE1 is an upstream effector of VEGF, as well as other molecules that relate to angiogenesis and the tumor microenvironment, it is also being studied as a possible treatment for age-related macular degeneration and diabetic retinopathy. This paper reviews all of APE1’s functions, while heavily focusing on its redox activities. It also discusses APE1’s altered expression in many cancers and the therapeutic potential of selective inhibition of redox regulation, which is the subject of intense preclinical studies

Guidance of Developing Motor Neurons into the Periphery

Motor neurons (MNs) are a diverse class of cells that originate in the central nervous system and project to muscles in the periphery. The development of all MNs subtypes begins with Sonic Hedgehog (Shh) signaling in the spinal cord and then progresses to increasingly specific guidance signaling systems. MN subtypes are classified by the combined activities of transcription factors and molecular signaling systems that determine axon trajectory. Molecular cues have been attributed to the organization of MNs into columns within the spinal cord and then into specific motor pools. These cues have also been shown to be responsible for axon guidance into the periphery and important for axons to innervate the correct targets. Despite advances in research on specific guidance cues used by different subdivisions of MNs, it is still not fully understood how signaling systems work with one another in the same environment to guide different classes of MNs to their respective muscle targets

North American Indigenous Adolescent Substance Use

Objectives—To investigate growth in problem drinking and monthly marijuana use among North American Indigenous adolescents from the upper Midwest and Canada. Methods—Panel data from a community-based participatory research project includes responses from 619 adolescents residing on or near 7 different reservations/reserves. All respondents were members of the same Indigenous cultural group. Results—Rates of problem drinking and monthly marijuana use increased steadily across the adolescent years, with fastest growth occurring in early adolescence (before age 15). In general, female participants reported higher rates of substance use prior to age 15; however, male reports of use surpassed those of females in later adolescence. Conclusions—Results of this study highlight the importance of early adolescent substance use prevention efforts and the possible utility of gender responsive programming