Oleksandr Ekshyyan

Apoptosis: A Key in Neurodegenerative Disorders

Apoptosis is an important process in the development of the nervous system. Typically, approximately 50% of the neurons apoptose during neurogenesis before the nervous system matures. However, recent paradigms implicate premature apoptosis and/or aberrations in the fine control of neuronal apoptosis in the pathogenesis of a variety of neurodegenerative disorders such as Alzheimers disease, Parkinsons disease, Huntingtons disease, amyotrophic lateral sclerosis, spinal muscular atrophy, stroke, brain trauma, spinal cord injury, and diabetic neuropathy. This review will focus on the current concepts salient to understanding the apoptosis death program, the mediators and control of cellular apoptosis, and the relationship between aberrant apoptosis and genesis of neurodegenerative disorders. The discussion will also highlight current advances in methodology, such as utilization of neuronal cell lines and mutant animal models, in investigations of neuronal apoptotic death. The knowledge of apoptosis mechanisms could underpin the basis for development of novel therapeutic strategies and treatment modalities that are directed at control of the neuronal apoptotic death program.

APOPTOSIS IN ACUTE AND CHRONIC NEUROLOGICAL DISORDERS

Programmed cell death or apoptosis is a physiologically important process in neurogenesis wherein approximately 50% of the neurons apoptose during maturation of the nervous system. However, premature apoptosis and/or aberrations in apoptosis control contribute to the pathogenesis of a variety of neurological disorders including acute brain injury such as trauma, spinal cord injury, ischemic stroke and ischemia/reperfusion as well as chronic disease states such as Alzheimers, Parkinsons, Huntingtons, amyotrophic lateral sclerosis, spinal muscular atrophy, and diabetic neuropathy. The current review will focus on two major topics, namely, the general concepts of our current understanding of the apoptosis death machinery, its mediators and regulation, and the relationship between aberrant apoptosis and genesis of neurodegenerative disorders. This knowledge of apoptosis mechanisms will underpin the basis for development of novel therapeutic strategies and treatment modalities that are directed at control of the neuronal apoptotic death program.

Comparison of radiosensitizing effects of the mammalian target of rapamycin inhibitor CCI-779 to cisplatin in experimental models of head and neck squamous cell carcinoma

To determine if the mammalian target of rapamycin (mTOR) inhibitor CCI-779 can sensitize head and neck squamous cell carcinoma (HNSCC) to radiotherapy (XRT) and compare the radiosensitizing effects to cisplatin with its known considerable toxicity. Radiosensitizing effects of CCI-779 were assayed on HNSCC cell lines in vitro. CCI-779 (5 mg/kg), cisplatin (1 mg/kg), and XRT (2 Gy) alone and in combination were evaluated for antitumor activity in mice bearing FaDu and SCC40 xenografts. Effects of CCI-779 on radiation-induced activation of the Akt/mTOR pathway were analyzed. Although CCI-779 did not sensitize HNSCC cells to ionizing radiation in vitro, combination of CCI-779 and XRT significantly augmented the in vivo tumor growth-inhibitory effects of XRT and CCI-779 (P < 0.05). In addition, CCI-779 + XRT suppressed tumor growth more effectively than cisplatin + XRT (P < 0.05). CCI-779 + XRT significantly improved survival compared with XRT alone in both cisplatin-sensitive FaDu (P < 0.01) and cisplatin-resistant SCC40 (P < 0.05) xenograft mice. There were no additional benefits of adding cisplatin to CCI-779 + XRT. CCI-779 significantly attenuated irradiation-induced up-regulation of the mTOR pathway, increased apoptosis and displayed potent antiangiogenic activity in FaDu xenografts that was further enhanced by its combination with XRT (P < 0.05), which may explain the mechanism of its selective radiosensitizing effects in vivo and not in vitro. Antitumor activity of XRT was enhanced when combined with CCI-779 in HNSCC xenograft model. CCI-779 + XRT showed antitumor activity superior to conventional chemoradiotherapy with cisplatin. These results pave the way for clinical trials using molecular targeted therapy with CCI-779 in combination with XRT for HNSCC treatment. [Mol Cancer Ther 2009;8(8):2255–65]

Teasing out the best molecular marker in the AKT/mTOR pathway in head and neck squamous cell cancer patients.

No reliable molecular biomarker is currently available for clinical application in the management of head and neck cancer patients. The AKT/mTOR pathway is activated in 90% to 100% of head and neck squamous cell cancer (HNSCC) and could be promising biomarkers closely linked to cancer incidence.

Pharmacodynamic evaluation of temsirolimus in patients with newly diagnosed advanced-stage head and neck squamous cell carcinoma

Activation of the mammalian target of rapamycin (mTOR) pathway in surgical margins of head and neck squamous cell carcinoma (HNSCC) is a predictor of recurrence and patients with minimal residual disease may benefit from adjuvant therapy with temsirolimus, an mTOR inhibitor.

Curcumin Inhibits UV Radiation–Induced Skin Cancer in SKH-1 Mice

Objective As skin cancer incidence increases, research has focused on novel chemopreventive agents that inhibit tumor formation. In prior experimentation, curcumin, a naturally occurring food substance and anticarcinogenic agent, inhibited cutaneous squamous cell carcinoma xenograft growth. We hypothesize curcumin will inhibit UVB radiation–induced skin cancer growth in mice, approximating a human chemopreventive model. Study Design Randomized experimental animal and laboratory study. Setting Louisiana State University Health Sciences Center-Shreveport, Louisiana. Subjects and Methods SKH-1 mice were pretreated with oral or topical curcumin or oral or topical control (n = 11/group) for 14 days. Mice received UVB radiation 3 times weekly for 24 weeks or were not radiated. Number of tumors formed and time to tumor onset for each mouse were recorded through tumor harvest after week 24. Tumor multiplicity and time to tumor onset were compared. Results Time to tumor onset was significantly shorter in control mice compared to mice receiving either oral (P = .025) or topical (P = .015) curcumin. A significant difference in the average number of tumors formed per mouse was seen, as fewer tumors were formed in the oral curcumin (P = .01) and topical curcumin (P = .01) groups, compared with respective controls. No significant difference in average number of tumors per mouse was seen between oral and topical curcumin (P = .56), suggesting that both routes were equally effective. Conclusion Curcumin appears to inhibit skin cancer formation and prolong time to tumor onset when administered by either an oral or topical route. These data suggest that curcumin may have chemopreventive potential against skin cancer, necessitating future experimentation with human subjects.

Anti-lymphangiogenic properties of mTOR inhibitors in head and neck squamous cell carcinoma experimental models

BackgroundTumor dissemination to cervical lymph nodes via lymphatics represents the first step in the metastasis of head and neck squamous cell carcinoma (HNSCC) and is the most significant predictor of tumor recurrence decreasing survival by 50%. The lymphatic suppressing properties of mTOR inhibitors are not yet well understood.MethodsLymphatic inhibiting effects of rapamycin were evaluated in vitro using two lymphatic endothelial cell (LEC) lines. An orthotopic mouse model of HNSCC (OSC-19 cells) was used to evaluate anti-lymphangiogenic effects of rapamycin in vivo. The incidence of cervical lymph node metastases, numbers of tumor-free lymphatic vessels and those invaded by tumor cells in mouse lingual tissue, and expression of pro-lymphangiogenic markers were assessed.ResultsRapamycin significantly decreased lymphatic vascular density (p = 0.027), reduced the fraction of lymphatic vessels invaded by tumor cells in tongue tissue (p = 0.013) and decreased metastasis-positive lymph nodes (p = 0.04). Rapamycin also significantly attenuated the extent of metastatic tumor cell spread within lymph nodes (p < 0.0001). We found that rapamycin significantly reduced LEC proliferation and was correlated with decreased VEGFR-3 expression in both LEC, and in some HNSCC cell lines.ConclusionsThe results of this study demonstrate anti-lymphangiogenic properties of mTOR inhibitors in HNSCC. mTOR inhibitors suppress autocrine and paracrine growth stimulation of tumor and lymphatic endothelial cells by impairing VEGF-C/VEGFR-3 axis and release of soluble VEGFR-2. In a murine HNSCC orthotopic model rapamycin significantly suppressed lymphovascular invasion, decreased cervical lymph node metastasis and delayed the spread of metastatic tumor cells within the lymph nodes.

Topical Curcumin-Based Cream Is Equivalent to Dietary Curcumin in a Skin Cancer Model

Skin squamous cell carcinoma (SCC), the most common cancer in the USA, is a growing problem with the use of tanning booths causing sun-damaged skin. Antiproliferative effects of curcumin were demonstrated in an aggressive skin cancer cell line SRB12-p9 (P < 0.05 compared to control). Topical formulation was as effective as oral curcumin at suppressing tumor growth in a mouse skin cancer model. Curcumin at 15 mg administered by oral, topical, or combined formulation significantly reduced tumor growth compared to control (P = 0.004). Inhibition of pAKT, pS6, p-4EBP1, pSTAT3, and pERK1/2 was noted in SRB12-p9 cells post-curcumin treatment compared to control (P < 0.05). Inhibition of pSTAT3 and pERK1/2 was also noted in curcumin-treated groups in vivo. IHC analysis revealed human tumor specimens that expressed significantly more activated pERK (P = 0.006) and pS6 (P < 0.0001) than normal skin samples. This is the first study to compare topical curcumin to oral curcumin. Our data supports the use of curcumin as a chemopreventive for skin SCC where condemned skin is a significant problem. Prevention strategies offer the best hope of future health care costs in a disease that is increasing in incidence due to increased sun exposure.

Efficacy and comparative effectiveness of sirolimus as an anticancer drug

To evaluate antitumor efficacy of the generic mammalian target of rapamycin (mTOR) inhibitor sirolimus in preclinical animal models of head and neck squamous cell carcinoma (HNSCC) and compare its effects with those of the patented analogue temsirolimus.

Photopreventive Effect and Mechanism of AZD4547 and Curcumin C3 Complex on UVB-Induced Epidermal Hyperplasia

Aggressive cutaneous squamous cell carcinoma (cSCC) of the skin is the second most common type of skin cancer in the United States due to high exposure to ultraviolet B (UVB) radiation. In our previous studies, Curcumin C3 complex (C3), a standardized preparation of three curcumonoids, delayed UVB-induced tumor incidence and inhibited multiplicity. Exposure to UVB activates mTOR and FGFR signaling that play a key role in skin tumorigenesis. The purpose of this study was to investigate the efficacy of C3 complex to afford protection against acute UVB-induced hyperproliferation by targeting the mTOR and FGFR signaling pathways. Pretreatment with C3 complex significantly inhibited UVB-induced FGF-2 induction, FGF-2–induced cell proliferation, progression and colony formation, mTORC1 and mTORC2 activation, and FGFR2 phosphorylation in the promotion-sensitive JB6 cells epithelial cells. Further, FGFR was critical for UVB-induced mTOR activation, suggesting an important role of FGFR2 in UVB-induced mTOR signaling. SKH-1 mice pretreated with C3 (15 mg/kg/b.w.) for 2 weeks followed by a single exposure to UVB (180 mj/cm2) significantly attenuated UVB-induced mTORC1, mTORC2, and FGFR2 activation. To further assess the role of FGFR in UVB-induced hyperproliferation, SKH-1 mice were pretreated with AZD4547 (5 mg/kg/b.w.); a selective pan-FGFR kinase inhibitor followed by single exposure to UVB (180 mj/cm2). AZD4547 significantly inhibited UVB-induced mTORC1 and mTORC2 activation, epidermal hyperplasia and hyperproliferation. Our studies underscore the importance of FGFR signaling in UVB-induced acute skin changes and the role of FGFR/mTOR signaling in mediating the effects of C3 complex in the pathogenesis of skin cancer. Cancer Prev Res; 9(4); 296–304. ©2016 AACR.