Molecular Pathways in Tumor Cell Invasion and Migration. This diagram illustrates the complex intracellular signaling pathways that govern the invasion and migration of tumor cells. Key components include the endothelin-1 (ET-1) signaling through endothelin A receptor (ETAR) and endothelin B receptor (ETBR), which leads to actin polymerization via multiple pathways. Proteins like RhoC, RhoA, Rac1, and Cdc42 are small GTPases that play pivotal roles in cytoskeletal dynamics. ROCK1/2 are Rho-associated protein kinases involved in actin-myosin contraction. LIMK and p-cofilin are implicated in actin filament stabilization and turnover. mDia2, IQGAP, N-WASP, WAVE, and the Arp2/3 complex are crucial for actin nucleation and polymerization, forming structures such as filopodia and lamellipodia. These processes are aided by the release of matrix metalloproteinases (MMPs) like MMP1, MMP13, MMP14, and MMP10, which remodel the extracellular matrix to facilitate tumor cell movement. (ET-1: Endothelin-1; ETAR: Endothelin A receptor; RhoC, RhoA, Rac1, Cdc42: Small GTPases involved in cytoskeletal organization; ROCK1/2: Rho-associated protein kinases; LIMK: LIM domain kinase; p-cofilin: phosphorylated cofilin; mDia2: Mammalian diaphanous-related formin 2; IQGAP: IQ motif containing GTPase activating protein; N-WASP: Neural Wiskott-Aldrich syndrome protein; WAVE: WASP family verprolin-homologous protein; Arp2/3: Actin-related protein 2/3 complex; MMPs: Matrix metalloproteinases)