Abstract
Topoisomerases have been shown to have roles in cancer progression. Here, we have examined the effect of cryptolepine, a plant alkaloid, on the growth of human non-melanoma skin cancer cells (NMSCC) and underlying mechanism of action. For this purpose SCC-13 and A431 cell lines were used as an in vitro model. Our study reveals that SCC-13 and A431 cells express higher levels as well as activity of topoisomerase (Topo I and Topo II) compared with normal human epidermal keratinocytes. Treatment of NMSCC with cryptolepine (2.5, 5.0 and 7.5 µM) for 24 h resulted in marked decrease in topoisomerase activity, which was associated with substantial DNA damage as detected by the comet assay. Cryptolepine induced DNA damage resulted in: (i) an increase in the phosphorylation of ATM/ATR, BRCA1, Chk1/Chk2 and γH2AX; (ii) activation of p53 signaling cascade, including enhanced protein expressions of p16 and p21; (iii) downregulation of cyclin-dependent kinases, cyclin D1, cyclin A, cyclin E and proteins involved in cell division (e.g., Cdc25a and Cdc25b) leading to cell cycle arrest at S-phase; and (iv) mitochondrial membrane potential was disrupted and cytochrome c released. These changes in NMSCC by cryptolepine resulted in significant reduction in cell viability, colony formation and increase in apoptotic cell death.
Keywords:
DNA damage; apoptosis; cell cycle; cryptolepine; skin cancer; topoisomerase.
MeSH terms
-
Alkaloids / pharmacology*
-
Antineoplastic Agents, Phytogenic / pharmacology*
-
Apoptosis / drug effects
-
BRCA1 Protein / genetics
-
BRCA1 Protein / metabolism
-
Cell Line
-
Cell Line, Tumor
-
Checkpoint Kinase 1 / genetics
-
Checkpoint Kinase 1 / metabolism
-
Checkpoint Kinase 2 / genetics
-
Checkpoint Kinase 2 / metabolism
-
Comet Assay
-
Cyclin-Dependent Kinase Inhibitor p16 / genetics
-
Cyclin-Dependent Kinase Inhibitor p16 / metabolism
-
Cyclin-Dependent Kinase Inhibitor p21 / genetics
-
Cyclin-Dependent Kinase Inhibitor p21 / metabolism
-
DNA Fragmentation / drug effects
-
DNA Topoisomerases, Type I / genetics*
-
DNA Topoisomerases, Type I / metabolism
-
DNA Topoisomerases, Type II / genetics*
-
DNA Topoisomerases, Type II / metabolism
-
Gene Expression Regulation, Neoplastic
-
Histones / genetics
-
Histones / metabolism
-
Humans
-
Indole Alkaloids / pharmacology*
-
Keratinocytes / drug effects*
-
Keratinocytes / metabolism
-
Keratinocytes / pathology
-
Organ Specificity
-
Quinolines / pharmacology*
-
Signal Transduction
-
Topoisomerase Inhibitors / pharmacology*
-
Transcription Factors / genetics
-
Transcription Factors / metabolism
-
Tumor Suppressor Protein p53 / genetics
-
Tumor Suppressor Protein p53 / metabolism
Substances
-
ATMIN protein, human
-
Alkaloids
-
Antineoplastic Agents, Phytogenic
-
BRCA1 Protein
-
BRCA1 protein, human
-
CDKN2A protein, human
-
Cyclin-Dependent Kinase Inhibitor p16
-
Cyclin-Dependent Kinase Inhibitor p21
-
H2AX protein, human
-
Histones
-
Indole Alkaloids
-
Quinolines
-
Topoisomerase Inhibitors
-
Transcription Factors
-
Tumor Suppressor Protein p53
-
cryptolepine
-
Checkpoint Kinase 2
-
CHEK1 protein, human
-
CHEK2 protein, human
-
Checkpoint Kinase 1
-
DNA Topoisomerases, Type I
-
DNA Topoisomerases, Type II