Antibody blockade of the Cripto CFC domain suppresses tumor cell growth in vivo

Abstract

Cripto, a cell surface-associated protein belonging to the EGF-CFC family of growth factor-like molecules, is overexpressed in many human solid tumors, including 70-80% of breast and colon tumors, yet how it promotes cell transformation is unclear. During embryogenesis, Cripto complexes with Alk4 via its unique cysteine-rich CFC domain to facilitate signaling by the TGF-β ligand Nodal. We report, for the first time to our knowledge, that Cripto can directly bind to another TGF-β ligand, Activin B, and that Cripto overexpression blocks Activin B growth inhibition of breast cancer cells. This result suggests a novel mechanism for antagonizing Activin signaling that could promote tumorigenesis by deregulating growth homeostasis. We show that an anti-CFC domain antibody, A8.G3.5, both disrupts Cripto-Nodal signaling and reverses Cripto blockade of Activin Binduced growth suppression by blocking Cripto's association with either Alk4 or Activin B. In two xenograft models, testicular and colon cancer, A8.G3.5 inhibited tumor cell growth by up to 70%. Both Nodal and Activin B expression was found in the xenograft tumor, suggesting that either ligand could be promoting tumorigenesis. These data validate that functional blockade of Cripto inhibits tumor growth and highlight antibodies that block Cripto signaling mediated through its CFC domain as an important class of antibodies for further therapeutic development.

Cripto regulates skeletal muscle regeneration and modulates satellite cell determination by antagonizing myostatin

“…Interestingly, in addition to its obligate role as a Nodal/ GDF1/GDF3 coreceptor, Cripto can antagonize signaling by activins and TGF-β (13)(14)(15). GDF8/myostatin is a member of the TGF-β superfamily that has been implicated in the negative regulation of muscle growth and regeneration (36).…”

“…In contrast to its coreceptor function, Cripto is able to antagonize signaling of other members of the TGF-β family (i.e., activins and TGF-β). This inhibitory activity of Cripto results in a reduced ability to form an active ActRII/ActRIB receptor complex (13)(14)(15).…”

Nodal and ALK7 Inhibit Proliferation and Induce Apoptosis in Human Trophoblast Cells

“…Nodal may also be involved in regulating placental function since, in the rat, it has been suggested that Nodal may inhibit the differentiation of stem trophoblast cells into giant cells (11). Recently, Nodal mRNA has been detected in a number of cell lines originating from mouse mammary gland (34) and human ovary (35), suggesting that Nodal also plays a role in adult life. However, no functional studies have been reported on the role of Nodal in mammalian cells during adult life.…”

Activin/Nodal signalling before implantation: setting the stage for embryo patterning

“…Activin is however antagonized by another secreted molecule, called Follistatin. There is also evidence that Cripto can inhibit signalling from Activin, TGF-b and Myostatin, which have in common to signal via Smad2/3 without requiring an EGF-CFC co-receptor to interact with their receptor complex [15][16][17][18].…”