Role of Kras Mutation on Desensitizing B2-Adrengic Receptor Signaling Blockade in Colorectal Cancer Cells

The signaling of stress-upregulated catecholamines-activated β1- and β2-adrenergic receptors (β1/2-ARs) have been shown to correlate with cancer progressions. Our previous study showed that β2-AR, not β1-AR, is a survival-dependent signaling in colorectal cancer (CRC) cells-carrying wild-type KRAS instead of mutated KRAS expression. Selective β2-AR blockade suppresses the growth of CRC cells-harboring wild-type KRAS, not mutated KRAS, via inhibiting EGFR-Akt/ERK1/2 signaling on inducing cell cycle arrest and apoptosis, suggesting that the expression of active KRAS mutation provides the extra survival signaling to avoid the death of CRC cells upon β2-AR blockade. If β1/2-ARs blocker can be utilized to treat KRAS-mutated CRC, it will have great clinical benefit in CRC patients due to the highly clinical safety and low cost of β1/2-ARs blocker. However, the function of KRAS mutation in desensitizing β2-AR blockade-mediated growth inhibition on CRC is unknown. Our recent preliminary data showed that β2-AR blockade by ICI-118,551, a selective β2-AR antagonist, dose-dependently enhanced the formation of LC3-II, an autophagy maker, in various KRAS-mutated but not KRAS wild-type CRC cell lines, indicating the specific phenomena of β2-AR blockade in activating autophagy in KRAS-mutated CRCs. Furthermore, in KRAS-mutated CRC HCT116 cells, ICI-118,551 stimulated the autophagic LC3 puncta formation, and autophagic inhibitor, hydroxychloroquine, accelerated ICI-118,551-activated LC3-II generation in activating autophagic flux. Moreover, β2-AR knockdown was similar to ICI-118,551 stimulation that induced LC3-II increase in HCT116 cells; and the enforced expression of mutated KRAS desensitized ICI-118,551-mediated viability suppression in β2-AR blockade sensitivity wild-type KRAS CRC HT29 cells, which is followed by the increment of autophagy. These data indicated the specificity of β2-AR blockade in inducing autophagy that may mediate the desensitization of β2-AR blockade on CRC’s viability. Mechanically, ICI-118,551 treatment decreased ERK1/2, AKT, and mTOR phosphorylations and P62 expression in HCT116 cells. Also, inhibitors of ERK1/2, PI3K, and autophagy synergistically enhanced the growth suppression and apoptosis of ICI-118,551 in HCT116 cells, indicating that co-targeting survival autophagy signaling can resensitization of β2-AR blockade for treating CRC cells. In order to target β2-AR signaling for treating KRAS-mutated CRC, it is important to understand β2-AR/KRAS/autophagy signal axis in CRC cells, which might reveal the therapeutic insights on β2-AR for treating malignant CRC in patients. Therefore, four specific aims of this study are proposed, including to investigate β2-AR-mediated regulation of autophagic homeostasis in CRC cells, the molecular mechanism of active KRAS mutation on β2-AR blockade-induced autophagy in CRC cells, the function of mutated KRAS expression in β2-AR blockade-mediated autophagy and growth suppression in CRCs in in vitro and in vivo, and co-targeting of β2-AR, autophagy, and mutated KRAS signals on treating KRAS-mutated CRC cells in in vitro and in vivo.

Project ID:PC10907-1544
External Project ID:MOST109-2320-B182-012