Growth suppression and cell death by pyridoxal is dependent on p53 in the human breast cancer cell line MCF-7

Effect of pyridoxine or cobalamin supplementation on apoptosis and cell cycle progression in a human glioblastoma cell line

Glioblastoma is the most aggressive type of brain tumor, with current therapies failing to significantly improve patient survival. Vitamins have important effects on cellular processes that are relevant for tumor development and progression.

AIM

The present study explored the effect of pyridoxine or cobalamin supplementation on the viability and cell cycle progression of human glioblastoma cell line U-87 MG.

METHOD

Cell cultures were treated with increasing concentrations of pyridoxine or cobalamin for 24-72 h. After supplementation, cell viability and cell cycle progression were assessed by spectrophotometry and flow cytometry. Analysis of Bcl-2 and active caspase 3 expression in supplemented cells was performed by western blot.

RESULT

The results show that pyridoxine supplementation decreases cell viability in a dose and time dependent manner. Loss of viability in pyridoxin-supplemented cells is probably related to less cell cycle progression, higher active caspase 3 expression and apoptosis. In addition, Bcl-2 expression did not appear to be altered by vitamin supplementation, but active caspase 3 expression was significantly increased in pyridoxine-, but not cobalamin-supplemented cells, furthermore, cobalamin inhibited the pyridoxine cytotoxicity in the cell viability assay when combined.

CONCLUSION

The results suggest that pyridoxine supplementation promotes apoptosis in human glioblastoma-derived cells and may be useful to enhance the effect of cytotoxic therapies in vivo.

Identification of vitamin B6 as a PD-L1 suppressor and an adjuvant for cancer immunotherapy

Interaction of programmed death-ligand 1 (PD-L1) and programmed death-1 (PD-1) inhibits T cell activation. Tumor tissues can evade immune surveillance by expressing higher levels of PD-L1. Identification of potential regulators of PD-L1 through natural metabolites may contribute to discovering new drugs for immunotherapy. By using a metabolite library screen, we showed that pyridoxal (PL) significantly suppresses PD-L1 expression. Mechanistically, PL accelerates PD-L1 degradation in a proteasome-dependent manner, and STUB1 serves as an E3 ligase during the process. Functionally, PL enhances T cell killing activity by blocking the PD-1/PD-L1 signaling pathway. Thus, we have identified PL as an inhibitor of PD-L1, which provides a feasible option for combination immunotherapy.

Pyridoxine induces monocyte-macrophages death as specific treatment of acute myeloid leukemia

Acute myeloid leukemia (AML) is an aggressive hematological malignancy that gradually develops resistance to current chemotherapy treatments. The available chemotherapy drugs show serious non-specific cytotoxicity to healthy normal cells, resulting in relapse and low survival rates. Natural small molecules with less toxicity and high selectivity for AML are urgently needed. In this study, we confirmed that pyridoxine (vitamin B6) selectively induces monocyte macrophages to undergo programmed cell death in two different modes: caspase-3-dependent apoptosis in U937 cells or GSDME-mediated pyroptosis in THP-1 cells. Further molecular analysis indicated that blocking the caspase pathway could switch the death to MLKL-dependent necroptosis and subsequent extensive inflammatory response. Pyridoxine also delayed the disease progression in a THP-1 leukemia mouse model. In addition, it induced the death of primary AML cells from AML patients by activating caspase-8/3. Overall, our results identify pyridoxine, a low-toxicity natural small molecule, as a potential therapeutic drug for AML treatment.

The effects of vitamin B6 compounds on cell proliferation and melanogenesis in B16F10 melanoma cells

B16F10 murine melanoma cells are frequently used for the study of cancer and melanogenesis. The cells are usually cultured in Dulbecco's Modified Eagle Medium, with the addition of 20 µM pyridoxal (PL) or pyridoxine (PN) for vitamin B₆. The difference between these vitamin B₆ compounds is thought not to affect cell proliferation, whereas their influence on other physiological effects is poorly understood. In the present study, the effects of PL and PN on cell proliferation and melanogenesis in B16F10 cells were compared. At 500 µM PL significantly suppressed cell growth but the growth inhibitory effect of PN was weak. Although neither of the vitamin B₆ compounds affected cell growth at 20 µM, melanogenesis was suppressed by 20 µM PL compared with the effect of PN. In addition, the expression levels of tyrosinase, which is the rate-limiting enzyme, correlated with the melanin content. The results of the present study indicate that PL may be more useful for melanoma therapy and suppression of skin pigmentation than PN. The results also signify the importance of medium selection for cell culture.

Morusin suppresses breast cancer cell growth in vitro and in vivo through C/EBPβ and PPARγ mediated lipoapoptosis

Background

Breast cancer is the most fatal malignant cancer among women, the conventional therapeutic modalities of it are limited. Morusin possesses cytotoxicity against some cancer cells in vitro. The purpose of this study is to test the growth inhibition effect of morusin on human breast cancer growth in vitro and in vivo and to explore the potential mechanism of its action.

Methods

The growth inhibition effect of morusin on human breast cancer cells in vitro and in vivo were tested by cell cytotoxicity, colony formation inhibition, adipogenic differentiation, apoptosis induction, and tumor growth inhibition in vivo assays. The potential molecular mechanisms underlying the growth inhibition effect of morusin on human breast cancer cells in vitro and in vivo were investigated with Western blotting evaluation of expression levels of transcription factors, C/EBPβ and PPARγ, adipogenic and apoptotic proteins in morusin treated breast cancer cells and tumor tissues.

Results

Morusin inhibited breast cancer cells growth in vitro and in vivo; it induced adipogenic differentiation, apoptosis and lipoapoptosis of cancer cells.

Conclusions

Morusin has the potential to inhibit human breast cancer cell growth in vitro and in vivo through C/EBPβ and PPARγ mediated lipoapoptosis.