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Effect of telomere and telomerase interactive agents on human tumor and normal cell lines
S Y Rha1, E Izbicka, R Lawrence
1Cancer Therapy & Research Center, Institute for Drug Development, The University of Texas Health Science Center at San Antonio, 78229, USA. srha@saci.org
Abstract:
Shortening of telomeres along with an up-regulation of telomerase is implicated in the immortality of tumor cells. Targeting either telomeres or telomerase with specific compounds has been proposed as an anticancer strategy. Because telomerase activity and telomeres are found in normal cells, telomere or telomerase targeting agents could induce side effects in normal tissues. We evaluated the effects of telomere and telomerase interactive agents in human tumor and normal cell lines to try to determine the potential side effects those agents might induce in patients. Toxicity of the G-quadruplex interactive porphyrins (TMPyP4, TMPyP2) and azidothymidine (AZT) were tested using a cell-counting technique against normal human cell lines (CRL-2115 and CRL-2120, fibroblasts; NHEK-Ad, adult keratinocytes; CCL-241, small intestinal cells; NCM 460, colonic mucosal epithelial cells) and human tumor cell lines (MDA-MB 231 and Hs 578T, breast cancer; SK-N-FI, neuroblastoma; HeLa, cervix cancer; MIA PaCa-2, pancreatic cancer; HT-29 and HCT-116, colon cancer; DU 145, prostatic cancer cell line). Telomerase activity of these cell lines was measured by a non-PCR-based conventional assay. The effects of TMPgammaP2, TMPyP4, and AZT were also evaluated against normal human bone marrow specimens, using a granulocyte-macrophage colony-forming assay (CFU-GM). AZT showed very low cytotoxic effects against normal and tumor cell lines, with the IC50 values above 200 microM. The IC50 values for TMPyP2 and TMPyP4 in normal human cell lines were in the range of 2.9-48.3 microM and 1.7-15.5 microM, respectively, whereas in tumor cell lines the IC50 values were 11.4-53 microM and 9.0-28.2 microM, respectively. Within the tissue types, keratinocytes were more sensitive to TMPyP4 than fibroblasts, and small intestinal cells were more sensitive than colonic mucosal epithelial cells. The IC50 for TMPyP2 and TMPyP4 in the normal marrow colony-forming assays were 19.3 +/- 5.1 microM and 47.9 +/-1.0 microM, respectively. In conclusion, the in vitro cytotoxicity of the telomere interactive agent TMPyP4 is comparable in human tumor and normal cell lines, which indicates that TMPyP4 could have effects on normal tissues.
Insights
Telomere-targeting agents like TMPyP4 show similar toxicity in cancer and normal cells, suggesting potential side effects. Azidothymidine (AZT) demonstrated minimal cytotoxicity, making it a safer alternative for cancer therapy research.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Tumor cell immortality is linked to telomere shortening and telomerase upregulation.
- Targeting telomeres or telomerase is a proposed anticancer strategy.
- Potential side effects in normal tissues are a concern due to telomere and telomerase presence in healthy cells.
Purpose of the Study:
- To evaluate the in vitro effects of telomere and telomerase interactive agents on human tumor and normal cell lines.
- To determine potential side effects of these agents on normal tissues.
- To compare the cytotoxicity of G-quadruplex interactive porphyrins (TMPyP4, TMPyP2) and azidothymidine (AZT).
Main Methods:
- Cell counting assay to assess toxicity in normal (fibroblasts, keratinocytes, intestinal, colonic cells) and tumor cell lines (breast, neuroblastoma, cervix, pancreas, colon, prostate).
- Non-PCR-based conventional assay to measure telomerase activity.
- Granulocyte-macrophage colony-forming assay (CFU-GM) to evaluate effects on normal human bone marrow specimens.
Main Results:
- Azidothymidine (AZT) exhibited very low cytotoxicity (IC50 > 200 microM) against both normal and tumor cells.
- TMPyP2 and TMPyP4 showed dose-dependent cytotoxicity, with IC50 values ranging from 1.7-53 microM across cell lines.
- TMPyP4 demonstrated comparable in vitro cytotoxicity in both normal and tumor cell lines, with higher sensitivity observed in keratinocytes and small intestinal cells compared to fibroblasts and colonic cells, respectively. Bone marrow progenitor cells also showed sensitivity.
Conclusions:
- The in vitro cytotoxicity of TMPyP4 is similar in human tumor and normal cell lines.
- TMPyP4 may cause adverse effects on normal tissues.
- AZT presents a potentially safer profile due to its low cytotoxicity, warranting further investigation for anticancer applications.