Amanda N King

University of Michigan, Ann Arbor, Michigan, United States

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Publications (4)20.43 Total impact

  • [Show abstract] [Hide abstract] ABSTRACT: Introduction: Cigarette smoke associated polycyclic aromatic hydrocarbons can induce key drug-metabolizing enzymes of cytochrome P450 and isoforms of the glucuronyl transferases families. These enzymes metabolize several systemic therapies for lung cancer. Induction of these enzymes may lead to accelerated clearance with resultant impact on systemic therapy efficacy and toxicity in smokers compared with nonsmokers. This article reviews published literature regarding the influence of smoking as it relates to alteration of metabolism of systemic therapy in lung cancer. Methods: A structured search of the National Library of Medicine's PubMed/MEDLINE identified relevant articles. Data were abstracted and analyzed to summarize the findings. Results: Studies that analyzed pharmacokinetic data were prospective. Smokers receiving erlotinib exhibited rapid clearance, requiring a higher dose to reach equivalent systemic exposure compared with nonsmokers. Smokers receiving irinotecan also demonstrated increased clearance and lower systemic exposure. There was no difference in clearance of paclitaxel or docetaxel in smokers. Chemotherapy-associated neutropenia was worse in nonsmokers compared with smokers in patients treated with paclitaxel, docetaxel, irinotecan, and gemcitabine. Conclusions: Systemic therapy for lung cancer has a narrow therapeutic index such that small changes in plasma concentrations or exposure in smokers may result in suboptimal therapy and poor outcomes. Smoking cessation must be emphasized at each clinical visit. However, prospective trials should take into consideration the effects of smoking history on drug pharmacokinetics and efficacy. The metabolizing enzyme phenotype in smokers may require individualized dose algorithms for specific agents.
    No preview · Article · Jul 2014 · Journal of thoracic oncology: official publication of the International Association for the Study of Lung Cancer
  • [Show abstract] [Hide abstract] ABSTRACT: The anti-proliferative effects of 1α,25-dihydroxyvitamin D(3) (1,25-D(3), calcitriol, the active form of vitamin D) are mediated by the nuclear vitamin D receptor (VDR). In the present study, we characterized VDR expression in lung adenocarcinoma (AC). We examined VDR mRNA expression using a quantitative real-time PCR (qRT-PCR) in 100 patients who underwent surgery for lung AC. In a subset of these patients (n=89), we examined VDR protein expression using immunohistochemistry. We also examined the association of VDR protein expression with circulating serum levels of 25-hydroxyvitamin D(3) (25-D(3)) and 1,25-D(3). The antiproliferative effects and cell cycle arrest of 1,25-D(3) were examined using lung cancer cell lines with high (SKLU-1) as well as low (A549) expression of VDR mRNA. Higher VDR expression correlates with longer survival after adjusting for age, sex, disease stage and tumor grade (HR 0.73, 95% CI 0.58-0.91). In addition, there was a positive correlation (r=0.38) between serum 1,25-D(3) and tumor VDR protein expression. A greater anti-proliferative effect of 1,25-D(3) was observed in high compared to low VDR-expressing cell lines; these effects corresponded to G1 cell cycle arrest; this was associated with a decline in cyclin D1, S-phase kinase protein 2 (Skp2), retinoblastoma (Rb) and minichromosome maintenance 2 (MCM2) proteins involved in S-phase entry. Increased VDR expression in lung AC is associated with improved survival. This may relate to a lower proliferative status and G1 arrest in high VDR-expressing tumors.
    No preview · Article · May 2012 · Lung cancer (Amsterdam, Netherlands)
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    [Show abstract] [Hide abstract] ABSTRACT: The active form of vitamin D, 1α,25-dihydroxyvitamin D(3) (1,25-D(3)), exerts antiproliferative effects in cancers, including lung adenocarcinoma (AC). CYP24A1 is overexpressed in many cancers and encodes the enzyme that catabolizes 1,25-D(3). The purpose of our study was to assess CYP24A1 as a prognostic marker and to study its relevance to antiproliferative activity of 1,25-D(3) in lung AC cells. Tumors and corresponding normal specimens from 86 patients with lung AC (stages I-III) were available. Affymetrix array data and subsequent confirmation by quantitative real time-PCR were used to determine CYP24A1 mRNA expression. A subsequent validation set of 101 lung AC was used to confirm CYP24A1 mRNA expression and its associations with clinical variables. The antiproliferative effects of 1,25-D(3) were examined using lung cancer cell lines with high as well as low expression of CYP24A1 mRNA. CYP24A1 mRNA was elevated 8- to 50-fold in lung AC (compared to normal nonneoplastic lung) and significantly higher in poorly differentiated cancers. At 5 years of follow-up, the probability of survival was 42% (high CYP24A1, n = 29) versus 81% (low CYP24A1, n = 57) (P = 0.007). The validation set of 101 tumors showed that CYP24A1 was independently prognostic of survival (multivariate Cox model adjusted for age, gender, and stage, P = 0.001). A549 cells (high CYP24A1) were more resistant to antiproliferative effects of 1,25-D(3) compared with SKLU-1 cells (low CYP24A1). CYP24A1 overexpression is associated with poorer survival in lung AC. This may relate to abrogation of antiproliferative effects of 1,25-D(3) in high CYP24A1 expressing lung AC.
    Full-text · Article · Feb 2011 · Clinical Cancer Research
  • [Show abstract] [Hide abstract] ABSTRACT: There is increasing evidence linking the incidence of certain cancers to low serum Vitamin D levels. The active metabolite of Vitamin D, calcitriol (1, 25-Dihydroxyvitamin D(3), 1,25(OH)(2)D(3)) apart from a crucial role in maintaining mineral homeostasis and skeletal functions, has antiproliferative, apoptosis and differentiation inducing as well as immunomodulatory effects in cancer. In studying the role of 1,25(OH)(2)D(3) in cancer, it is imperative to examine the potential pathways that control local tissue levels of 1,25(OH)(2)D(3). The enzyme CYP24A1 or 24-hydroxylase converts 1,25(OH)(2)D(3) to inactive calcitroic acid. Extra-renal production of this enzyme is observed and has been increasingly recognized as present in cancer cells. This enzyme is rate limiting for the amount of local 1,25(OH)(2)D(3) in cancer tissues and elevated expression is associated with an adverse prognosis. The gene that encodes CYP24A1 has been reported as an oncogene and may contribute to tumor aggressiveness by abrogating local anti-cancer effects of 1,25(OH)(2)D(3). It is imperative to study the regulation of CYP24A1 in cancer and especially the local metabolism of 1,25(OH)(2)D(3) in cancer cells. CYP24A1 may be a predictive marker of 1,25(OH)(2)D(3) efficacy in patients with cancer as an adjunctive therapy. The following review summarizes the available literature on CYP24A1 as it relates to 1,25(OH)(2)D(3) in cancer and outlines potential ways to inhibit CYP24A1 in an effort to improve the efficacy of exogenous 1,25(OH)(2)D(3).
    No preview · Article · Feb 2010 · Anti-cancer agents in medicinal chemistry