Luka Milas

University of Texas MD Anderson Cancer Center, Houston, Texas, United States

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Publications (382)1748.96 Total impact

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    ABSTRACT: Positive transcription elongation factor-b (P-TEFb) is a complex containing CDK9 and a cyclin (T1, T2 or K). The effect of inhibition of P-TEFb by 5,6-dichloro-l-β-D-ribofuranosyl benzimidazole (DRB) on cell radiosensitivity and the underlying mechanisms were investigated. Six human cancer cell lines were subjected to (3)H-uridine incorporation, cell viability and clonogenic cell survival assays; cell-cycle redistribution and apoptosis assay; western blots and nuclear 53BP1 foci analysis after exposing the cells to DRB with/without γ-radiation. DRB suppressed colony formation and enhanced radiosensitivity of all cell lines. DRB caused a further increase in radiation-induced apoptosis and cell-cycle redistribution depending on p53 status. DRB prolonged the presence of radiation-induced nuclear p53 binding protein-1 (53BP1) foci and suppressed the expression of sirtuin-1 (SIRT1) and casein kinase 2-alpha (CK2α), suggesting an inhibition of DNA repair processes. Our findings indicate that DRB has the potential to increase the efficacy of radiotherapy and warrants further investigation using in vivo tumor models. Copyright© 2014 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.
    Anticancer research 12/2014; 34(12):6981-9. · 1.83 Impact Factor
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    Lung Cancer 09/2013; 81(3). DOI:10.1016/j.lungcan.2013.06.006 · 3.96 Impact Factor
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    ABSTRACT: BACKGROUND AND PURPOSE: Although inhibition of epidermal growth factor receptor (EGFR) signaling during radiation led to improvement of tumor control and survival, novel strategies are needed to further improve the outcome of patients with locally advanced head and neck carcinoma. Because EGFR is known to interact with c-Src kinases, the present study investigated dasatinib (BMS-354825), an inhibitor of c-Src kinases, for its efficacy in enhancing radiosensitivity of human head and neck squamous cell carcinomas (HNSCC) in vitro and examined the underlying mechanisms for this effect. MATERIALS AND METHODS: Six HNSCC lines were exposed to dasatinib, radiation, or both, and assessed for c-Src and EGFR expression, cell survival and colony forming ability. Among these cell lines, HN-5 and FaDu lines were analyzed for induction of apoptosis, cell cycle re-distribution and for nuclear localization of EGFR, γ-H2AX and 53BP1 proteins. Immuno-precipitation and Western blots were performed to analyze the levels and binding of proteins involved in cell survival, apoptosis and DNA repair pathways. Suppression of c-Src by siRNA and subsequent clonogenic assay was performed in HN-5 cells. RESULTS: All six HNSCC lines that were examined expressed high levels of c-Src. Two (HN-5 and MDA-183) expressed higher levels of EGFR than other lines. Dasatinib suppressed cell survival of all cell lines tested independent of c-Src or EGFR levels but enhanced the radiosensitivity of HN-5 and MDA-183. HN-5 and FaDu were analyzed further. Dasatinib suppressed phosphorylation of c-Src in both cell lines, but decreased repair of radiation-induced DNA damage in HN-5 cells only as evidenced by suppression of c-Abl and Nbs-1 activity, inhibition of the association between c-Src and EGFR or Her-2, prolongation of nuclear γ-H2AX and 53BP1 foci and inhibition of EGFR nuclear localization and its association with DNA-PKcs. Finally, partial suppression of c-Src resulted in a small increase in HN-5 cell radiosensitivity. CONCLUSIONS: Our data demonstrate that dasatinib induces apoptosis and blocks DNA repair in EGFR-expressing HNSCC cells and improves radiotherapy outcome. These findings warrant further investigation using in vivo tumor models for potential translation into clinical testing.
    Radiotherapy and Oncology 09/2012; 105(2). DOI:10.1016/j.radonc.2012.08.010 · 4.36 Impact Factor
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    ABSTRACT: Targeting the epidermal growth factor receptor (EGFR) improved radiotherapy outcome by 10-15% in head and neck tumors (HNSCC). We tested the therapeutic benefits of co-targeting EGFR and insulin-like growth factor-1 receptor (IGF-1R) to further enhance tumor response to radiation. Mice bearing FaDu tumor xenografts were treated with ganitumab (previously known as AMG479, an anti-IGF-1R antibody), panitumumab (an anti-EGFR antibody), or both in combination with fractionated doses of radiation. Tumor growth delay and tumor cure/recurrence served as end-points. The best tumor growth delay was achieved when ganitumab and panitumumab were given concurrently with radiation. Tumor cure/recurrence studies showed that combining ganitumab, panitumumab and radiation resulted in significantly higher radiocurability rates than use of either of the agents given with radiation. These findings provide the rationale for clinical testing of the combination of ganitumab and panitumumab for the treatment of HNSCC.
    Anticancer research 08/2012; 32(8):3029-35. · 1.83 Impact Factor
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    ABSTRACT: Purpose: To test whether a cyclooxygenase-2 inhibitor (celecoxib) could reduce mortality resulting from radiation-induced pneumonitis. Methods and materials: Celecoxib was given to mice twice daily for 40 consecutive days starting on the day of local thoracic irradiation (LTI) or 40 or 80 days later. C3Hf/KamLaw mice were observed for morbidity, and time to death was determined. Results were analyzed using the Cox proportional hazards model. Results: Timing of celecoxib relative to LTI determined efficacy. A significant reduction in time to death was achieved only when celecoxib was started 80 days after LTI, corresponding to the time when pneumonitis is expressed. For these mice the reduction in mortality was quantified as a hazard ratio for mortality of treated vs untreated of 0.36 (95% confidence interval [CI] 0.24-0.53), thus significantly less than 1.0. Correspondingly, the median lethal dose for treated mice (12.9 Gy; 95% CI 12.55-13.25 Gy) was significantly (P=.026) higher than for untreated mice (12.4 Gy; 95% CI 12.2-12.65 Gy). Conclusions: Celecoxib significantly reduced lung toxicity when administered months after LTI when the deleterious effects of radiation were expressed. The schedule-dependent reduction in fatal pneumonitis suggests that celecoxib could be clinically useful by reintroduction of treatment months after completion of radiation therapy. These findings may be important for designing clinical trials using cyclooxygenase-2 inhibitors to treat radiation-induced lung toxicity as a complement to concurrent radiation therapy of lung cancers.
    International journal of radiation oncology, biology, physics 06/2012; 85(2). DOI:10.1016/j.ijrobp.2012.04.025 · 4.26 Impact Factor
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    ABSTRACT: Recent research on inhibitors of poly (ADP-ribose) polymerase (PARP) has demonstrated their potential for improving cancer therapy. They inhibit protein poly (ADP-ribosyl)ation and thus affect numerous molecular and cellular functions, including DNA repair and cell survival, that are critical for such physiological and patho-physiological states as carcinogenesis, inflammation, and resistance to cancer therapy. In this review, we describe the biological basis underlying the use of these agents in cancer therapy, providing data from preclinical studies that demonstrate the synergistic interaction of PARP inhibitors with radiation and chemotherapeutics. We also summarize initial clinical trials of PARP inhibitors for cancer treatment.
    American journal of clinical oncology 04/2012; 37(1). DOI:10.1097/COC.0b013e3182467dce · 3.06 Impact Factor

  • Radiotherapy and Oncology 03/2012; 102:S165-S166. DOI:10.1016/S0167-8140(12)70271-2 · 4.36 Impact Factor
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    ABSTRACT: Current chemotherapeutics are characterized by efficient tumor cell-killing and severe side effects mostly derived from off-target toxicity. Hence targeted delivery of these drugs to tumor cells is actively sought. In an in vitro system, we previously demonstrated that targeted drug delivery to cancer cells overexpressing epidermal growth factor receptor (EGFR+) can be achieved by poly(ethylene glycol)-functionalized carbon nanovectors simply mixed with a drug, paclitaxel, and an antibody that binds to the epidermal growth factor receptor, cetuximab. This construct is unusual in that all three components are assembled through noncovalent interactions. Here we show that this same construct is effective in vivo, enhancing radiotherapy of EGFR+ tumors. This targeted nanovector system has the potential to be a new therapy for head and neck squamous cell carcinomas, deserving of further preclinical development.
    ACS Nano 02/2012; 6(3):2497-505. DOI:10.1021/nn204885f · 12.88 Impact Factor
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    ABSTRACT: Purpose: Preclinical findings suggest that adding targeted therapies to combination radiation-chemotherapy can enhance treatment efficacy; however, this approach may enhance normal tissue toxicity. We investigated the maximum tolerated dose, dose-limiting toxicities, and response rate when the selective cyclo-oxygenase-2 inhibitor celecoxib is added to concurrent irinotecan, cisplatin, and radiation therapy for patients with inoperable stage II-III non-small cell lung cancer. Methods and materials: Eighteen patients were analyzed in a phase I clinical dose-escalation trial. Celecoxib was given daily beginning 5 days before radiation followed by maintenance doses for 12 weeks. Toxicity was graded with the Common Terminology Criteria for Adverse Events V3.0 and response with the World Health Organization system. Primary endpoints were maximum tolerated dose of celecoxib and treatment toxicity; secondary endpoints were response and survival rates. Results: The maximum tolerated dose of celecoxib was not reached, in part owing to discontinuation of the drug supply. At doses of 200 or 400 mg/day, no patients experienced any dose-limiting toxicity (acute grade ≥4 esophagitis or pneumonitis, neutropenic fever or thrombocytopenia requiring transfusion, or acute grade ≥3 diarrhea). Grade 3 toxicities were leukopenia (5 patients), fatigue (3), pneumonitis (2), dyspnea (1), pain (1), and esophageal stricture (1). Interestingly, pulmonary fibrosis (a late toxicity) was no more severe in the higher-dose (400-mg) group and may have been less common than in the lower-dose group. The clinical response rate was 100% (8 complete, 10 partial). Two-year rates were: overall survival 65%; local-regional control 69%; distant metastasis-free survival 71%; and disease-free survival 64%. Conclusions: Although preliminary, our results suggest that adding celecoxib to concurrent chemoradiation for inoperable NSCLC is safe and can improve outcome without increasing normal tissue toxicity.
    Frontiers in Oncology 12/2011; 1:52. DOI:10.3389/fonc.2011.00052
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    ABSTRACT: The poly-(ADP-ribose) polymerase (PARP) inhibitor, MK-4827, is a novel potent, orally bioavailable PARP-1 and PARP-2 inhibitor currently in phase I clinical trials for cancer treatment. No preclinical data currently exist on the combination of MK-4827 with radiotherapy. The current study examined combined treatment efficacy of MK-4827 and fractionated radiotherapy using a variety of human tumor xenografts of differing p53 status: Calu-6 (p53 null), A549 (p53 wild-type [wt]) and H-460 (p53 wt) lung cancers and triple negative MDA-MB-231 human breast carcinoma. To mimic clinical application of radiotherapy, fractionated radiation (2 Gy per fraction) schedules given once or twice daily for 1 to 2 weeks combined with MK-4827, 50 mg/kg once daily or 25 mg/kg twice daily, were used. MK-4827 was found to be highly and similarly effective in both radiation schedules but maximum radiation enhancement was observed when MK-4827 was given at a dose of 50 mg/kg once daily (EF = 2.2). MK-4827 radiosensitized all four tumors studied regardless of their p53 status. MK-4827 reduced PAR levels in tumors by 1 h after administration which persisted for up to 24 h. This long period of PARP inhibition potentially adds to the flexibility of design of future clinical trials. Thus, MK-4827 shows high potential to improve the efficacy of radiotherapy.
    Investigational New Drugs 11/2011; 72(8 Supplement). DOI:10.1007/s10637-011-9770-x · 2.92 Impact Factor

  • Molecular Cancer Therapeutics 11/2011; 10(Supplement 1):A145-A145. DOI:10.1158/1535-7163.TARG-11-A145 · 5.68 Impact Factor
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    ABSTRACT: Lung cancer is the leading cause of cancer death in most developed countries. The prognosis remains poor with an overall survival rate at 5 years of only about 15%. Between 70 and 85% of all cases are histologically classified as non-small cell lung carcinoma (NSCLC). Radiation therapy has traditionally been the treatment of choice for locally advanced disease and medically inoperable early stage NSCLC. However radiation therapy alone was not effective treatment for patients with locally advanced NSCLC. The addition of cytotoxic drugs to radiotherapy considerably improves treatment outcome, and the combination of chemotherapy with radiotherapy has become common practice for the treatment of locally advanced lung cancer. The addition of chemotherapy to radiotherapy has two principal objectives: one, to increase the chance of local tumor control and two, to eliminate metastatic disease outside of the radiation field. Several randomized trials have shown improvement of local control and survival by application of concurrent chemotherapy rather than sequential chemotherapy followed by radiation treatment. This combined treatment approach results in median survival times of 13 to 14 months and survival rates at 5 years as high as 15 to 20%. These improvements have been achieved by using standard chemotherapeutic agents, primarily cisplatin-based drug combinations. However, concurrent chemoradiotherapy has increased significant normal tissue toxicity such as esophagitis and pneumonitis. Therefore normal tissue protectors without protective cancer cells became necessary to improve therapeutic ratio. We will discuss mechanism and efficacy of Amifostine to protect normal tissue followed by other normal tissue protectors or molecular targeted treatment without increasing normal tissue damage e.g., prostanoids (COX-2) inhibitors, Growth factor and Cytokines inhibitors, Basic and other inhibitors targeting Fibroblast Growth Factor, Karatinocyte Growth Factors, Epidermoid Growth Factor Receptor, Pentoxifylline, Angiotensin-Converting Enzyme Flavopiridol Poly(ADP-Ribose) Polymerase, Bcl-2 , and Efaproxaril, as well as Radioprotective Gene Therapy/ Antioxidant Therapy: and Superoxide Dismutase
    09/2011: pages 223-245;
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    ABSTRACT: The present study investigated the effect of AC480, a small molecule pan-HER tyrosine kinase inhibitor, on in vitro radiosensitivity and in vivo radioresponse of a human head and neck squamous cell carcinoma cell line. HN-5 cells were exposed to γ-radiation with and without AC480 and assayed for proliferation, clonogenic survival, apoptosis, cell cycle distribution, and DNA damage. The cells were analyzed by immunoprecipitation and western blotting for proteins involved in apoptosis, cell cycle regulation, and the EGFR pathway. The effect of AC480 on tumor radioresponse was assessed by tumor growth delay assay using HN5 tumor xenografts generated in nude mice. At the molecular level, in HN-5 cells the agent inhibited the expression of pEGFR, pHER2, cyclins D and E, pRb, pAkt, pMAPK, pCDK1 and 2, CDK 6, and Ku70 proteins. The drug also induced accumulation of cells in the G1 cell cycle phase, inhibited cell growth, enhanced radiosensitivity, and prolonged the presence of γ-H₂AX foci up to 24 h after radiation. AC480 did not increase the percentage of cells undergoing radiation-induced apoptosis. The drug given before and during irradiation improved the radioresponse of HN5 tumors in vivo. AC480 significantly enhanced the radiosensitivity of HN-5 cells, expressing both EGFR and Her2. The mechanisms involved in the enhancement included cell cycle redistribution and inhibition of DNA repair. Both in vitro and in vivo data from our study suggest that AC480 has potential to increase tumor response to radiotherapy.
    Investigational New Drugs 08/2011; 29(4):554-61. DOI:10.1007/s10637-010-9389-3 · 2.92 Impact Factor

  • Cancer Research 07/2011; 71(8 Supplement):2487-2487. DOI:10.1158/1538-7445.AM2011-2487 · 9.33 Impact Factor
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    ABSTRACT: To assess radiosensitzing potential of huachansu (HCS) and delineate the underlying mechanisms. Lung cancer cell lines were exposed to HCS, radiation or both and subjected to survival assays, Western blots, apoptosis assay and immunocytochemical analysis. HCS suppressed the viability of all three lung lines tested and enhanced radiosensitivity of H460 and A549 (wild-type p53) only with no effect on H1299 (p53 null) cells. HCS prolonged the presence of radiation-induced γH2AX foci and increased radiation-induced apoptosis. Western blots showed that HCS increased cleaved caspase-3 and cleaved poly-(ADP-ribose) polymerase (PARP) levels, as well as reducing BCL-2 and p53 protein levels in H460 cells. HCS-enhanced radiosensitivity of human lung cancer lines appeared to be p53-dependent. Inhibition of DNA repair and increase in radiation-induced apoptosis may have served as underlying mechanisms. These data suggest that HCS may have potential to improve the efficacy of radiotherapy.
    Anticancer research 06/2011; 31(6):2141-8. · 1.83 Impact Factor

  • Cancer Research 04/2011; 71(8 Supplement):2488-2488. DOI:10.1158/1538-7445.AM2011-2488 · 9.33 Impact Factor

  • Cancer Research 04/2011; 71(8 Supplement):2509-2509. DOI:10.1158/1538-7445.AM2011-2509 · 9.33 Impact Factor

  • Cancer Research 04/2011; 71(8 Supplement):2507-2507. DOI:10.1158/1538-7445.AM2011-2507 · 9.33 Impact Factor
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    ABSTRACT: We investigated whether vandetanib, an inhibitor of the tyrosine kinase activities of vascular endothelial growth factor receptor-2 (VEGFR-2), epidermal growth factor receptor (EGFR), and rearranged during transfection (RET), could augment the antitumor activity of radiation with or without cisplatin in preclinical in vitro and in vivo models of human head and neck squamous cell carcinoma (HNSCC). OSC-19 and HN5 HNSCC cells that were cisplatin and radioresistant were treated with vandetanib, cisplatin, and radiation alone or in combination in vitro and in vivo using an orthotopic nude mouse model. Treatment effects were assessed using clonogenic survival assay, tumor volume, bioluminescence imaging, tumor growth delay, survival, microvessel density, tumor and endothelial cell apoptosis, and EGFR and Akt phosphorylation data. Vandetanib plus cisplatin radiosensitized HNSCC cells in vitro and in vivo. The combination treatment with vandetanib, cisplatin, and radiation was superior to the rest of treatments (including the double combinations) in antitumoral effects, prolonging survival, decreasing cervical lymph node metastases in vivo. It also increased both tumor and tumor-associated endothelial cell apoptosis and decreased microvessel density in vivo. An analysis of tumor growth delay data revealed that vandetanib plus cisplatin enhanced radioresponse in vivo. All vandetanib-containing treatments inhibited EGFR and Akt phosphorylation in vitro and in vivo. The addition of vandetanib to combination therapy with cisplatin and radiation was able to effectively overcome cisplatin and radioresistance in in vitro and in vivo models of HNSCC. Further study of this regimen in clinical trials may be warranted.
    Clinical Cancer Research 02/2011; 17(7):1815-27. DOI:10.1158/1078-0432.CCR-10-2120 · 8.72 Impact Factor

  • Cancer Research 01/2011; 70(8 Supplement):488-488. DOI:10.1158/1538-7445.AM10-488 · 9.33 Impact Factor

Publication Stats

12k Citations
1,748.96 Total Impact Points


  • 1974-2014
    • University of Texas MD Anderson Cancer Center
      • • Department of Experimental Radiation Oncology
      • • Division of Radiation Oncology
      • • Department of Radiotherapy
      Houston, Texas, United States
  • 2012
    • Rice University
      • Department of Chemistry
      Houston, Texas, United States
  • 1990-2007
    • University of Houston
      Houston, Texas, United States
  • 1999
    • Carl Gustav Carus-Institut
      Pforzheim, Baden-Württemberg, Germany
    • University of Chicago
      • Department of Radiation & Cellular Oncology
      Chicago, IL, United States
  • 1997
    • Houston Zoo
      Houston, Texas, United States
  • 1995
    • Loyola University Chicago
      Chicago, Illinois, United States
  • 1984-1988
    • University of Texas Health Science Center at Houston
      Houston, Texas, United States
  • 1985
    • Hospital of the University of Pennsylvania
      Filadelfia, Pennsylvania, United States
  • 1979
    • University of Zagreb
      • Department of Pathophysiology
      Zagrabia, Grad Zagreb, Croatia
  • 1973-1974
    • Ruder Boskovic Institute
      Zagrabia, Grad Zagreb, Croatia