17β-estradiol Enhances 5-Fluorouracil Anti-Cancer Activities in Colon Cancer Cell Lines

Abstract

Background: 5-Fluorouracil (5-FU) represents one of the major constituents of chemotherapy combination regimens in colon cancer (CRC) treatments; however, this regimen is linked with severe adverse effects and chemoresistance. Thus, developing more efficient approaches for CRC is urgently needed to overcome these problems and improve the patient survival rate. Currently, 17β-estradiol (E2) has gained greater attention in colon carcinogenesis, significantly lowering the incidence of CRC in females at reproductive age compared with age-matched males.

Aims: This study measured the effects of E2 and/or 5-FU single/dual therapies on cell cycle progression and apoptosis against human HT-29 female and SW480 male primary CRC cells versus their impact on SW620 male metastatic CRC cells.

Methods: The HT-29, SW480, and SW620 cells were treated with IC₅₀ of E2 (10 nM) and 5-FU (50 μM), alone or combined (E+F), for 48 h before cell cycle and apoptosis analyses using flow cytometry.

Results: The data here showed that E2 monotherapy has great potential to arrest the cell cycle and induce apoptosis in all the investigated colon cancer cells, with the most remarkable effects on metastatic cells (SW620). Most importantly, the dual therapy (E+F) has exerted anti-cancer activities in female (HT-29) and male (SW480) primary CRC cells by inducing apoptosis, which was preferentially provoked in the sub-G₁ phase. However, the dual treatment showed the smallest effect in SW620 metastatic cells.

Conclusion: this is the first study that demonstrated that the anti-cancer actions of 17β-estradiol and 5-Fluorouracil dual therapy were superior to the monotherapies in female and male primary CRC cells; it is proposed that this treatment strategy could be promising for the early stages of CRC. At the same time, 17β-estradiol monotherapy could be a better approach for treating the metastatic forms of the disease. Nevertheless, additional investigations are still required to determine their precise therapeutic values in CRC.

Keywords: 17β-estradiol; 5-Fluorouracil; apoptosis; cell cycle; colon cancer cells; sub-G1 phase.

Figure 1

Percentage of cells (mean ± SD of three independent experiments in triplicate) in the cell cycle phases (sub-G₁, G₀/G1, S, G₂/M) in untreated control cells (CT) and following treatments with 7β-estradiol (E2) at 10 nM and 5-Fluorouracil (5-FU) at 50 µM, alone and in combination (E+F), for 48 h in the: (a) HT-29 female and (b) SW480 male primary colon cancer cells and in the (c) SW620 male metastatic colon cancer cells, using the PI staining and flow cytometry analysis. Data were represented in the bar chart; symbols such as the green asterisk (*) were used when there was a significant increase, while the red asterisk (*) was used when there was a significant decrease. Results were considered statistically significant when p ≤ 0.05; monotherapies were statistically compared to CT only, while dual therapy was statistically compared to CT and monotherapies (Section 2.6).

Figure 2

Percentage of the live cells and early and late apoptotic cells alongside dead cells (mean ± SD of three independent experiments in triplicate) in untreated control cells (CT) and following treatments with 7β-estradiol (E2) at 10 nM and 5-Fluorouracil (5-FU) at 50 µM at µM alone and in combination (E+F) for 48 in the: (a) HT-29 female and (b) SW480 male primary colon cancer cells, and in the (c) SW620 male metastatic colon cancer cells, using the AV/PI staining and flow cytometry analysis. Data were represented in the bar chart; symbols such as the green asterisk (*) were used when there was a significant increase, while the red asterisk (*) was used when there was a significant decrease. Results were considered statistically significant when p ≤ 0.05; monotherapies were statistically compared to CT only, while dual therapy was statistically compared to the monotherapies and CT (Section 2.6).