Acquired resistance to molecularly targeted therapies for cancer

Acquired resistance to molecularly targeted therapies remains a formidable challenge in the treatment of cancer, despite significant advancements over the last several decades. We critically evaluate the evolving landscape of resistance mechanisms to targeted cancer therapies, with a focus on the genetic, molecular, and environmental contributors across a variety of malignancies. Intrinsic mechanisms such as mutations, drug and drug target modifications, and, notably, the activation of the mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/Akt pathways are mechanisms different malignancies use to combat therapeutic effectiveness. Furthermore, extrinsic alterations to the tumor microenvironment contribute to therapeutic resistance. We highlight similarities and differences in mechanisms across a wide spectrum of cancers including hematologic malignancies, non-small cell lung cancer, gastrointestinal, breast, and prostate cancers, pancreatic, ovarian, endometrial, and intracranial gliomas. Emerging strategies to overcome resistance, including multi-targeted approaches, combination therapies, and exploitation of synthetic lethality, are all critically discussed. We advocate for a nuanced understanding of resistance mechanisms as a cornerstone for developing future therapeutic strategies, emphasizing the necessity for integrated approaches that encompass genomic insights and precision medicine to outpace the dynamic and complex nature of cancer evolution and therapy resistance.