ABSTRACT
BACKGROUND: Haploinsufficiency may contribute to the development of breast cancer among women with a BRCA1 mutation. Thus, interventions that enhance BRCA1 expression may represent avenues for prevention. Studies have shown that 3,3'-diindolylmethane (DIM) can upregulate BRCA1 expression in breast cancer cells. This has yet to be demonstrated in vivo. METHODS: We conducted a study to evaluate the ability of oral DIM to upregulate BRCA1 mRNA expression in white blood cells. A total of 18 women were enroled in the study, including 13 BRCA1 mutation carriers who received 300 mg per day of Rx Balance BioResponse DIM for 4-6 weeks (intervention group) and 5 BRCA1 mutation carriers who did not take DIM (control group). BRCA1 mRNA expression was assessed at baseline and at 4-6 weeks by real-time, quantitative PCR and the relative change in BRCA1 mRNA expression (that is, 2(-ΔΔCT)) was calculated. RESULTS: The relative change in BRCA1 mRNA expression among women in the intervention group achieved borderline significance (P paired t-test=0.05). In the intervention group, BRCA1 mRNA expression increased in 10 of the participants, decreased in 2 and remained unchanged in 1 of the participants following DIM intervention (P sign test=0.02). On average, women in the intervention group experienced a 34% increase in BRCA1 mRNA expression (range -24 to 194%). There was no significant difference in the relative change in BRCA1 mRNA expression among women in the control group (P paired t-test=0.45). CONCLUSIONS: Under the tested conditions, oral DIM was associated with an increase in BRCA1 mRNA expression in women with a BRCA1 mutation. The possibility of mitigating the effect of an inherited deleterious BRCA1 mutation by increasing the physiologic expression of the gene and normalising protein levels represents a clinically important paradigm shift in the prevention strategies available to these high-risk women. Future studies with a larger sample size and higher doses of DIM are warranted.
Subject(s)
Anticarcinogenic Agents/administration & dosage , BRCA1 Protein/genetics , Breast Neoplasms/prevention & control , Gene Expression/drug effects , Indoles/administration & dosage , RNA, Messenger/metabolism , Administration, Oral , Adult , Aged , BRCA1 Protein/metabolism , Female , Humans , Middle Aged , Mutation , RNA, Messenger/genetics , Up-RegulationABSTRACT
UNLABELLED: Indole-3-carbinol (I3C) when given orally is converted to diindolylmethane (DIM) and other oligomers catalyzed by stomach acid. This suggests that DIM is the predominant active agent and that I3C is a precursor, 'pro-drug' in vivo. However, in cell culture studies carried out in neutral solutions, I3C has been considered fully active. MATERIALS AND METHODS: The stability of I3C in cell culture media was studied. RESULTS: In the 8 different cell culture media tested, greater than 50% dimerization of I3C into DIM occurred in 24 hours. At 48 hour, greater than 60% conversion was found. When neutral synthetic cerebrospinal fluid (CSF) or peritoneal fluid (PF) was studied, a large peak, tentitively identified as I3C's linear trimer (LTR) conversion product by mass spectra, and two smaller peaks, were seen. When CSF or PF was diluted 1:1 with media, the formation of these additional peaks was diminished. CONCLUSION: Because of the greater biologic potency of DIM when studied in parallel with I3C in vitro, this extent of dimerization shows that DIM rather than I3C is the active agent in cell culture studies.
