A novel podophyllotoxin-derived compound GL331 is more potent than its congener VP-16 in killing refractory cancer cells.
OBJECTIVE
GL331 is a new homolog of VP-16, and has demonstrated more efficacious anti-cancer activity in both the in vitro and in vivo lymphoma systems. To extensively explore GL331's clinical value, we furthermore evaluate the cytotoxicity and apoptosis-inducing activity of GL331 in several human cell lines from cancers that are not normally treated with VP-16.


METHODS
By MTT and clonogenic survival assays, the cytotoxicities of GL331 and VP-16 were evaluated in a variety of cell lines including nasopharyngeal, hepatocellular, gastric, colon, cervical, and neuroblastoma cancer types. Western blot analysis was performed to detect the MDR-1 level in these cell lines. By Annexin V-staining flow cytometry and detection of DNA ladders, the apoptosis-inducing activities of GL331 and VP-16 were also evaluated.


RESULTS
GL331 showed more efficacy than its congener VP-16 in killing cancer cells. The estimated ID50 of GL331 were 2.5 to 17-fold lowerthan those of VP-16. GL331 possessed more cell-killing activity even in MDR-1-overexpressing cell lines such as HCC36 and SW620. Its higher cytotoxicity could be attributed by the elevated ability to induce apoptotic cell death.


CONCLUSIONS
GL331's overriding drug resistance and higher cancer cell-killing activity suggest its superiority in clinical cancer therapy.
Huang
T S
TS
Cooperative Laboratory, Cancer Research Division, National Health Research Institutes, Taipei, Taiwan, Republic of China. tshuang@nhri.org.tw
Lee
C C
CC
Chao
Y
Y
Shu
C H
CH
Chen
L T
LT
Chen
L L
LL
Chen
M H
MH
Yuan
C C
CC
Whang-Peng
J
J
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis / Q000378:metabolism; D000972:Antineoplastic Agents, Phytogenic / Q000633:toxicity*; D017209:Apoptosis / Q000187:drug effects; D016923:Cell Death / Q000187:drug effects; D018432:Drug Resistance, Multiple; D004354:Drug Screening Assays, Antitumor; D005047:Etoposide / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000633:toxicity*; D006801:Humans; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D011034:Podophyllotoxin / Q000031:analogs & derivatives* / Q000633:toxicity*; D014407:Tumor Cells, Cultured
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000972:Antineoplastic Agents, Phytogenic; C121391:GL 331; D005047:Etoposide; D011034:Podophyllotoxin