Effects of interferon beta on transcobalamin II-receptor expression and antitumor activity of nitrosylcobalamin

J Natl Cancer Inst. 2002 Jul 3;94(13):1010-9. doi: 10.1093/jnci/94.13.1010.


Background: The ubiquitous plasma membrane transcobalamin II receptor (TC II-R) mediates uptake of cobalamin (Cbl; vitamin B12), an essential micronutrient. Tumors often require more Cbl than normal tissue, and increased Cbl uptake may result from increased TC II-R expression. To examine whether Cbl could therefore be used as a carrier molecule to target a chemotherapy drug, we tested an analogue of Cbl with nitric oxide as a ligand, nitrosylcobalamin (NO-Cbl). Because interferon beta (IFN-beta) has antitumor effects and increases expression of some membrane receptors, we examined whether it may enhance the effects of NO-Cbl.

Methods: Antiproliferative effects of NO-Cbl were assessed in 24 normal and cancer cell lines. Xenograft tumors of human ovarian cancer NIH-OVCAR-3 cells were established in athymic nude mice, and tumor growth was monitored after treatment with NO-Cbl and IFN-beta, both individually and concomitantly. TC II-R expression and apoptosis was monitored in vitro and in vivo. RNA protection assays and mitochondrial membrane potential assays were used to distinguish the extrinsic and intrinsic apoptotic pathways, respectively.

Results: Cancer cell lines were more sensitive to NO-Cbl (with ID(50)s [the dose that inhibits growth by 50%] as low as 2 microM) than normal cell lines (with ID(50)s of 85-135 microM). Single-agent NO-Cbl and IFN-beta treatment of NIH-OVCAR-3 xenografts induced tumor regression, whereas combination treatment induced tumor eradication. IFN-beta treatment increased TC II-R expression in vitro and uptake of [(57)Co]cobalamin in vivo. Compared with NIH-OVCAR-3 cells treated with NO-Cbl, cells treated with NO-Cbl and IFN-beta were more apoptotic and expressed higher mRNA levels of various apoptosis-associated genes. No changes in mitochondrial membrane potential were observed in cells treated with NO-Cbl.

Conclusion: NO-Cbl inhibited tumor growth in vivo by activating the extrinsic apoptotic pathway. The increased expression of TC II-R induced by IFN-beta resulted in enhanced antitumor effects with NO-Cbl both in vitro and in vivo.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Annexin A5 / metabolism
  • Antineoplastic Agents / pharmacology*
  • Antineoplastic Agents / therapeutic use
  • Apoptosis / physiology
  • Blotting, Western
  • Breast Neoplasms / metabolism
  • Breast Neoplasms / pathology
  • Breast Neoplasms / therapy*
  • Caspase 8
  • Caspase 9
  • Caspases / metabolism
  • Cell Division / drug effects
  • Combined Modality Therapy
  • Drug Synergism
  • Female
  • Humans
  • Immunoenzyme Techniques
  • Interferon-beta / therapeutic use*
  • Male
  • Melanoma / metabolism
  • Melanoma / pathology
  • Melanoma / therapy*
  • Membrane Potentials
  • Mice
  • Mice, Nude
  • Mitochondria / metabolism
  • Nitric Oxide / metabolism
  • Nitroso Compounds / pharmacology*
  • Ovarian Neoplasms / metabolism
  • Ovarian Neoplasms / pathology
  • Ovarian Neoplasms / therapy*
  • Receptors, Cell Surface / metabolism*
  • Rhodamines
  • Ribonuclease, Pancreatic / metabolism
  • Tumor Cells, Cultured / drug effects
  • Tumor Cells, Cultured / metabolism
  • Vitamin B 12 / analogs & derivatives*
  • Vitamin B 12 / pharmacology*


  • Annexin A5
  • Antineoplastic Agents
  • Nitroso Compounds
  • Receptors, Cell Surface
  • Rhodamines
  • nitrosylcobalamin
  • transcobalamin receptor
  • lissamine rhodamine B
  • Nitric Oxide
  • Interferon-beta
  • Ribonuclease, Pancreatic
  • CASP8 protein, human
  • CASP9 protein, human
  • Casp8 protein, mouse
  • Casp9 protein, mouse
  • Caspase 8
  • Caspase 9
  • Caspases
  • Vitamin B 12