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Differential inhibition of human cancer cell proliferation by citrus limonoids
1Texas A&M University-Kingsville Citrus Center, Weslaco, TX 78596, USA.
Abstract:
Limonoids have been shown to inhibit the growth of estrogen receptor-negative and -positive human breast cancer cells in culture. The primary objective of this study was to test the antiproliferative activity of limonoids (obacunone 17 beta-D-glucopyranoside, nomilinic acid 17 beta-D-glucopyranoside, limonin, nomilin, and a limonoid glucoside mixture), found in high concentrations in mandarin (Citrus reticulata Blanco), against a series of human cancer cell lines. The human cancer cell lines included leukemia (HL-60), ovary (SKOV-3), cervix (HeLa), stomach (NCI-SNU-1), liver (Hep G2), and breast (MCF-7). The growth-inhibitory effects of the four limonoids and the limonoid glucoside mixture against MCF-7 cells were significant, and the antiproliferative activity of the different citrus limonoids was also dose and time dependent. No significant effects were observed on growth of the other cancer cell lines treated with the four individual limonoids at 100 micrograms/ml. At 100 micrograms/ml, the limonoid glucoside mixture demonstrated a partial inhibitory effect on SKOV-3 cancer cells. With use of flow cytometry, it was found that all the limonoid samples could induce apoptosis in MCF-7 cells at relatively high concentrations (100 micrograms/ml). Considering the high concentration needed to induce apoptosis, it is unlikely that this is the primary mechanism of action for the cytotoxic effects seen with limonoids in this study. Further work is needed in this area to establish the mechanism of action of citrus limonoids on human breast cancer cells.
Insights
Citrus limonoids show antiproliferative effects against human breast cancer cells (MCF-7) in a dose-dependent manner. While apoptosis was observed at high concentrations, further research is needed to confirm the mechanism of action for these potent compounds.
Area of Science:
- Phytochemistry
- Cancer Biology
- Cellular Pharmacology
Background:
- Limonoids, naturally occurring compounds in citrus fruits like mandarin (Citrus reticulata Blanco), are known for their potential health benefits.
- Previous studies indicated limonoids can inhibit the growth of both estrogen receptor-negative and -positive human breast cancer cells in vitro.
Purpose of the Study:
- To evaluate the antiproliferative activity of specific limonoids and a limonoid glucoside mixture against various human cancer cell lines.
- To determine the dose and time dependency of the observed effects on cancer cell growth.
Main Methods:
- Testing of five citrus limonoids (obacunone 17 beta-D-glucopyranoside, nomilinic acid 17 beta-D-glucopyranoside, limonin, nomilin, and a limonoid glucoside mixture) against six human cancer cell lines (leukemia HL-60, ovary SKOV-3, cervix HeLa, stomach NCI-SNU-1, liver Hep G2, and breast MCF-7).
- Growth inhibition was assessed, and flow cytometry was used to investigate apoptosis induction in MCF-7 cells.
- Experiments were conducted at a concentration of 100 micrograms/ml for individual limonoids and the mixture.
Main Results:
- Significant growth inhibition was observed for the four individual limonoids and the limonoid glucoside mixture against human breast cancer (MCF-7) cells.
- The antiproliferative activity against MCF-7 cells was found to be dose and time dependent.
- No significant effects were noted on other tested cancer cell lines (HL-60, SKOV-3, HeLa, NCI-SNU-1, Hep G2) with individual limonoids at 100 µg/ml.
- The limonoid glucoside mixture showed partial inhibition of SKOV-3 cells at 100 µg/ml.
- Apoptosis was induced in MCF-7 cells by all tested limonoid samples at high concentrations (100 µg/ml), though this may not be the primary cytotoxic mechanism.
Conclusions:
- Citrus limonoids exhibit significant antiproliferative effects specifically against human breast cancer (MCF-7) cells.
- The observed cytotoxic effects at high concentrations may involve apoptosis, but further investigation is required to elucidate the precise mechanism of action.
- The differential activity across cancer cell lines suggests potential for targeted therapeutic development, warranting further research into citrus limonoids' anticancer properties.