In vitro inhibition of matrix metalloproteinases, invasion and growth of Fanconi anemia human FANCA and FANCC lymphoblasts by nutrient mixture.

AIM: Fanconi anemia is a rare genetic disorder with high propensity for development of cancers, such as aplastic anemia, leukemia and head and neck cancers. Collagen digesting matrix metalloproteinase (MMP) enzymes have been implicated in for their role in various malignancies and to promote metastasis. Biological agents that prevent extracellular matrix digestion by the MMPs have been shown to be promising therapeutic approaches to cancer. In this study, we investigated effects of a nutrient mixture (NM) containing, ascorbic acid, lysine, proline and green tea extract, on human FANCA and FANCC lymphoblasts for viability, MMP secretion and invasion. METHODS: Human FANCA lymphoblasts GM13022 and HCS536 were challenged with NM at concentration range within 10-1000 µg/ml. Cell toxicity was assessed by Trypan blue dye exclusion test. Invasion was evaluated through Matrigel and gelatinase zymography for MMP activity. RESULTS: NM was toxic in dose dependent mode to HCS536 cells but not to GM13022 cells. GM13022 cells but not HCS536 cells exhibited MMP-9 secretion, which was inhibited by NM. Matrigel invasion was inhibited in HCS536 cells at 100 and 500 µg/ml by 27% and 93%, respectively. In GM13022 cells, the NM showed completely blocked Matrigel invasion at 500 µg/ml. CONCLUSION: NM inhibited MMP secretion and Matrigel invasion in FANCA and inhibited invasion and induced toxicity in FANCC lymphoblasts. These results suggest that the NM may have therapeutic potential in Fanconi anemia associated neoplasia.

Salidroside stimulates DNA repair enzyme Parp-1 activity in mouse HSC maintenance.

Salidroside is a phenylpropanoid glycoside isolated from the medicinal plant Rhodiola rosea, which has potent antioxidant properties. Here we show that salidroside prevented the loss of hematopoietic stem cells (HSCs) in mice under oxidative stress. Quiescent HSCs were recruited into cell cycling on in vivo challenge with oxidative stress, which was blocked by salidroside. Surprisingly, salidroside does not prevent the production of reactive oxygen species but reduces hydrogen peroxide-induced DNA-strand breaks in bone marrow cells enriched for HSCs. We tested whether salidroside enhances oxidative DNA damage repair in mice deficient for 5 DNA repair pathways known to be involved in oxidative DNA damage repair; we found that salidroside activated poly(ADP-ribose)polymerase-1 (PARP-1), a component of the base excision repair pathway, in mouse bone marrow HSCs as well as primary fibroblasts and human lymphoblasts. PARP-1 activation by salidroside protects quiescent HSCs from oxidative stress-induced cycling in native animals and self-renewal defect in transplanted recipients, which was abrogated by genetic ablation or pharmacologic inhibition of PARP-1. Together, these findings suggest that activation of PARP-1 by salidroside could affect the homeostasis and function of HSCs and contribute to the antioxidant effects of salidroside.

Involvement of the Fanconi's anemia protein FAC in a pathway that signals to the cyclin B/cdc2 kinase.

Lymphoblastoid cell lines derived from patients with the chromosomal instability disorder Fanconi's anemia (FA) are hyperresponsive to G2 delay and apoptosis induced by cross-linking agents such as mitomycin C (MMC). Here, we investigated whether the protein defective in FA complementation group C (FA-C) cells functions in a pathway that signals to the cdc2 kinase complex, which controls mitotic progression. FA-C lymphoblasts treated with a low dose of MMC (1-5 microM, 1 h) exhibited a protracted G2-M arrest and subsequent apoptosis by 2 days after treatment. This G2-M arrest was mediated by persistent inactivation of the cyclin B1/cdc2 kinase complex characterized by both sustained accumulation of cyclin B1 and tyrosine phosphorylation of cdc2. In phenotypically corrected (wild-type) cells, the same treatment induced only temporal G2-M arrest, associated with a transient inactivation of the cyclin B1/cdc2 kinase complex, after which cells resumed cycling. Treatment with higher dosages (15-30 microM, 1 h) resulted in S-phase arrest and induced a similar high level of apoptosis in FA-C and wild-type cells, accompanied by degradation of cyclin B1 and dephosphorylation of cdc2. In low-dose treated G2-M-arrested FA-C cells, caffeine-dependent activation of cdc2 released the G2-M block but failed to protect against apoptosis, suggesting that apoptosis was not a direct consequence of persistent cdc2 kinase inactivation. Thus, at low doses of MMC, FA-C cells exhibit a unique cyclin B1/cdc2 response that is not observed in wild-type cells treated with an equitoxic high dosage of cross-linker. Although these results do not necessarily implicate a role for FAC in regulating cyclin B/cdc2 kinase activity, available evidence suggests that the FAC protein is involved in a cross-link damage avoidance pathway that signals to this kinase complex.