Kai Kraemer

Biological Activity of a Gallic Acid−Gelatin Conjugate

Goal of the present study was the characterization of the biological properties of a gelatin-gallic acid conjugate (Gel-GA) to evaluate its applicability in biomedicine and pharmacy. The macromolecular conjugate was synthesized by free radical grafting reaction between gelatin and gallic acid (GA) to form a covalent conjugate that was found to retain the antioxidant and enzymatic activities of free GA. In particular, the peroxynitrite scavenging power was found to be consistent with a IC(50) value of 2.17 ± 0.4 mg mL(-1). The enzymatic capacities of GA, which are regarded beneficial for cell functions, are partly retained in the Gel-GA conjugate. In particular, acetylcholinesterase inhibition (IC(50) of 7.1 ± 1.3 mg mL(-1)) implies the conjugates usefulness in the chemoprevention of Alzheimers disease, while the inhibition of α-amylase (IC(50) of 9.8 ± 1.1 mg mL(-1)) suggests that the conjugate can be a preferred alternative for inhibition of carbohydrate breakdown and control of glycemic index of food products. Finally, the anticancer activity of Gel-GA was proven in prostate carcinoma and renal cell carcinoma cell lines, confirming the potential of the proposed protein-polyphenol conjugate in medicine.

Delivery of carboplatin by carbon-based nanocontainers mediates increased cancer cell death

Since the activity of several conventional anticancer drugs is restricted by resistance mechanisms and dose-limiting side-effects, the design of nanocarriers seems to be an efficient and promising approach for drug delivery. Their chemical and mechanical stability and their possible multifunctionality render tubular nanomaterials, such as carbon nanotubes (CNTs) and carbon nanofibres (CNFs), promising delivery agents for anticancer drugs. The goal of the present study was to investigate CNTs and CNFs in order to deliver carboplatin in vitro. No significant intrinsic toxicity of unloaded materials was found, confirming their biocompatibility. Carboplatin was loaded onto CNTs and CNFs, revealing a loading yield of 0.20 mg (CNT-CP) and 0.13 mg (CNF-CP) platinum per milligram of material. The platinum release depended on the carrier material. Whereas CNF-CP marginally released the drug, CNT-CP functioned as a drug depot, constantly releasing up to 68% within 14 days. The cytotoxicity of CNT-CP and CNF-CP in urological tumour cell lines was dependent on the drug release. CNT-CP was identified to be more effective than CNF-CP concerning the impairment of proliferation and clonogenic survival of tumour cells. Moreover, carboplatin, which was delivered by CNT-CP, exhibited a higher anticancer activity than free carboplatin.

Microarray analyses in bladder cancer cells: Inhibition of hTERT expression down‐regulates EGFR

The human telomerase reverse transcriptase (hTERT) contributes to the immortal phenotype of the majority of cancers. Targeting hTERT by transfection with antisense oligonucleotides (AS‐ODNs) induced immediate growth inhibition in human bladder cancer (BCa) cells. The molecular basis of the antiproliferative capacity of hTERT AS‐ODNs was investigated by oligonucleotide microarray analyses and was compared to effects caused by siRNA‐mediated knock‐down of hTERT in EJ28 BCa cells. Two different AS‐ODNs—both down‐regulated the expression of hTERT—changed the expression of different genes mainly involved in stress response (including EGR1, ATF3 and GDF15), but without an association to telomerase function. This indicates that the immediate growth inhibition was caused, at least in part, by off‐target effects. In comparison to that the blockade of the expression of hTERT using 2 different siRNAs was accompanied by the down‐regulation of the oncogenes FOS‐like antigen 1 (FOSL1) and epidermal growth factor receptor (EGFR), known to be overexpressed in BCa. We show here for the first time that repression of the hTERT transcript number decreased the expression of EGFR both at the mRNA and protein levels, suggesting a potential new function of hTERT in the regulation of EGFR‐stimulated proliferation. Furthermore, the suppression of hTERT by siRNAs caused an enhancement of the antiproliferative capacity of the chemotherapeutics mitomycin C and cisplatin. The results presented herein may support the hypothesis that hTERT promotes the growth of tumor cells by mechanisms independent from telomere lengthening. The detailed clarification of these processes will shed light on the question, whether telomerase inhibitors might constitute suitable anticancer tools.

Telomerase inhibition by synthetic nucleic acids and chemosensitization in human bladder cancer cell lines.

The knockdown of genes that are over-expressed in cancer, and function in tumor onset and/or progression, is an attractive tool to impair the growth of tumor cells. Synthetic nucleic acids such as antisense oligodeoxynucleotides (AS-ODNs) or small-interfering RNAs (siRNAs) were applied against different tumor-associated transcripts, including the human telomerase reverse transcriptase (hTERT), to inhibit the proliferation of tumor cells and to sensitize them against chemotherapeutic (CT) agents. The efficacy of nucleic acid-based inhibitors was evaluated in vitro by determining the extent of down-regulation of the respective target mRNA and protein expression as well as by extensively investigating growth properties (e.g., viability, proliferation, apoptosis, and cell-cycle distribution) of the affected tumor cells. Methods for a successful down-regulation of hTERT and for the quantitative determination of resulting effects on cellular growth were described herein.

Carbon Nanotubes Filled with Carboplatin: Towards Carbon Nanotube-Supported Delivery of Chemotherapeutic Agents

Thanks to their capillary-like structure CNTs provide a well-characterized container material for hosting miscellaneous fillings. Here we present basic studies on the use of CNTs for drug delivery. By introducing carboplatin, an anticancer drug, into the CNTs via a wet chemical approach, drug-filled nanotubes have been produced. The maintenance of the structure of carboplatin was proven using electron energy loss spectroscopy and X-ray photoelectron spectroscopy. It was shown that the drug is released into cell culture medium leading to cell death. Cell viability assays performed with bladder cancer cells EJ28 demonstrated the cytotoxicity of CNTs filled with carboplatin. For comparison a reference of unfilled, open ended CNTs did not affect the cell viability. These results point out the general capabilities of CNTs as nanocarriers for drug delivery.

Antisense Oligonucleotides: Insights from Preclinical Studies and Clinical Trials

Since the first pioneering studies using antisense oligonucleotides (ASOs) in the late 1970s, thousands of publications followed, demonstrating the remarkableness of antisense action and its enormous application spectrum. In 1998, Fomivirsen (Vitravene) was the first, and to date the only ASO that gained approval by the US Food and Drug Administration (FDA) for intravitreous treatment of cytomegalovirus-induced retinitis in patients with acquired immune deficiency syndrome (AIDS). Meanwhile, efforts regarding ASO research decreased and investigations shifted to other molecules, e.g., small interfering RNAs, because ASO-related problems such as insufficient efficacy and off-target effects are not yet overcome. However, newer studies using ASOs with improved chemistry or approaches combining ASO treatment with other therapies, such as chemotherapy or radiation, might bring ASOs back into the spotlight. This chapter will focus on current in vivo studies and clinical trials of promising ASOs.