RESUMO
Although amplifications and mutations in receptor tyrosine kinases (RTKs) act as bona fide oncogenes, in most cancers, RTKs maintain moderate expression and remain wild-type. Consequently, cognate ligands control many facets of tumorigenesis, including resistance to anti-RTK therapies. Herein, we show that the ligands for the RTKs MET and RON, HGF and HGFL, respectively, are synthesized as inactive precursors that are activated by cellular proteases. Our newly generated HGF/HGFL protease inhibitors could overcome both de novo and acquired cetuximab resistance in colorectal cancer (CRC). Conversely, HGF overexpression was necessary and sufficient to induce cetuximab resistance and loss of polarity. Moreover, HGF-induced cetuximab resistance could be overcome by the downstream MET inhibitor, crizotinib, and upstream protease inhibitors. Additionally, HAI-1, an endogenous inhibitor of HGF proteases, (i) was downregulated in CRC, (ii) exhibited increased genomic methylation that correlated with poor prognosis, (iii) HAI-1 expression correlated with cetuximab response in a panel of cancer cell lines, and (iv) exogenous addition of recombinant HAI-1 overcame cetuximab resistance in CC-HGF cells. Thus, we describe a targetable, autocrine HAI-1/Protease/HGF/MET axis in cetuximab resistance in CRC.
Assuntos
Neoplasias Colorretais , Transdução de Sinais , Humanos , Cetuximab/farmacologia , Proteínas Proto-Oncogênicas c-met/genética , Proteínas Proto-Oncogênicas c-met/metabolismo , Resistencia a Medicamentos Antineoplásicos/genética , Neoplasias Colorretais/tratamento farmacológico , Neoplasias Colorretais/genética , Neoplasias Colorretais/metabolismo , Inibidores de Proteases/farmacologia , Peptídeo Hidrolases/metabolismo , Linhagem Celular Tumoral , Fator de Crescimento de Hepatócito/genética , Fator de Crescimento de Hepatócito/metabolismo , Fator de Crescimento de Hepatócito/farmacologiaRESUMO
Nicotine is the major addictive component of cigarette smoke and although it is not considered carcinogenic, it can enhance or inhibit cancer cell proliferation depending on the type of cancer. Nicotine mediates its effects through nicotinic acetylcholine receptors (nAChRs), which are expressed in many different neuronal and non-neuronal cell types. We observed that the nAChR α4, α5, α7 subunits were expressed in ovarian cancer (OC) cells. Nicotine inhibited the proliferation of SKOV3 and TOV112D OC cells, which have TP53 mutation and wild-type KRAS, but did not inhibit the proliferation of TOV21G or HEY OC cells, which have KRAS mutation and wild-type TP53. Exposure to nicotine for 96 h led to a significant reduction in the amounts of activated extracellular signal-regulated kinase (ERK) and activated p38 mitogen-activated protein kinases (MAPKs) in SKOV3 cells, and in activated ERK in TOV112D cells. In addition, SKOV3 and TOV112D invasion and spheroid formation were substantially inhibited by siRNA knockdown of mixed lineage kinase 3 (MLK3), or MEK inhibition. Nicotine treatment reduced SKOV3 and TOV112D spheroid invasion and compaction but did not significantly affect spheroid formation. Furthermore, SKOV3 spheroid invasion was blocked by p38 inhibition with SB202190, but not by MEK inhibition with U0126; whereas TOV112D spheroid invasion was reduced by MEK inhibition, but not by p38 inhibition. These results indicate that nicotine can suppress spheroid invasion and compaction as well as proliferation in SKOV3 and TOV112D OC cells; and p38 and ERK MAPK signaling pathways are important mediators of these responses.
Assuntos
Nicotina/farmacologia , Neoplasias Ovarianas/tratamento farmacológico , Receptores Nicotínicos/efeitos dos fármacos , Transdução de Sinais/efeitos dos fármacos , Carcinoma Epitelial do Ovário/tratamento farmacológico , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Feminino , Humanos , Imidazóis/farmacologia , Neoplasias Ovarianas/metabolismo , Fosforilação/efeitos dos fármacos , Piridinas/farmacologia , Receptores Nicotínicos/metabolismo , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Delivery to the correct membrane domain in polarized epithelial cells is a critical regulatory mechanism for transmembrane proteins. The trafficking of these proteins is directed by short amino acid sequences known as sorting motifs. In six basolaterally-localized proteins lacking the canonical tyrosine- and dileucine-based basolateral sorting motifs, a monoleucine-based sorting motif has been identified. This review will discuss these proteins with an identified monoleucine-based sorting motif, their conserved structural features, as well as the future directions of study for this non-canonical basolateral sorting motif.