Activation of
KISS1 receptor (
KISS1R or GPR54) by its
ligands (
Kisspeptins) regulates a diverse function both in normal physiology and pathophysiology. In
cancer,
KISS1R has been implicated in
tumor angiogenesis and
metastasis, but a broader evaluation of
KISS1R in
tumorigenesis and
tumor progression is yet to be conducted. In this study, we used mouse models of
Kiss1r gene knockout and mouse mammary tumor virus-polyoma virus middle
T antigen (MMTV-PyMT)-induced
breast cancer to conduct such an evaluation.
Kiss1r heterozygosity in MMTV-PyMT mice was sufficient to attenuate
breast cancer initiation, growth, latency, multiplicity, and lung
metastasis. To confirm these effects and assess possible contributions of endogenous
ligands, we isolated primary
tumor cells from PyMT/
Kiss1r(+/+) and PyMT/
Kiss1r(+/-) mice and compared their phenotypes by in vitro and in vivo assays.
Kiss1r loss attenuated in vitro tumorigenic properties as well as
tumor growth in vivo in immunocompromised NOD.SCID/NCr mice.
Kiss1r activation in these cells, resulting from the addition of its
ligand Kisspeptin-10, resulted in RhoA activation and RhoA-dependent gene expression through the Gαq-p63RhoGEF signaling pathway. Anchorage-independent growth was tightly linked to dose-dependent regulation of RhoA by
Kiss1r. In support of these results,
siRNA-mediated knockdown of
KISS1R or inactivation of RhoA in human MCF10A breast epithelial cells overexpressing H-RasV12 was sufficient to reduce Ras-induced anchorage-independent growth. In summary, we concluded that
Kiss1r attenuation was sufficient to delay
breast tumor initiation, progression, and
metastasis through inhibitory effects on the downstream Gαq-p63RhoGEF-RhoA signaling pathway.