Inhibiting the RAS-PI3K pathway in cancer therapy (original) (raw)
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Will PI3K pathway inhibitors be effective as single agents in patients with cancer?
Oncotarget, 2011
The phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) axis regulates essential cellular functions including cell survival, proliferation, metabolism, migration, and angiogenesis. The PI3K pathway is activated in human cancers by mutation, amplification, and deletion of genes encoding components of this pathway. The critical role of PI3K in cancer has led to the development of drugs targeting the effector mechanisms of this signaling network. Recent studies have shown that inhibition at multiple levels of the PI3K pathway results in FOXO-dependent feedback reactivation of several receptor tyrosine kinases (RTKs) which, in turn, limit the sustained inhibition of this pathway and attenuates the action of therapeutic antagonists. This suggests that if used as single agents, PI3K pathway inhibitors may have limited clinical activity. We propose herein that to successfully target the output of the PI3K pathway in cancer cells, combination therapies that hinder these compensatory mechanisms should be used. Thus, combination therapies that target RTKs, PI3K, and mTOR activities may be required to maximize the clinical benefit derived from treatment with these inhibitors.
PI3 kinase inhibitors in the clinic: an update
Anticancer research, 2012
The phosphoinositide-3 kinase/protein kinase-B/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway has been identified as a key signaling pathway for important cellular functions such as growth control, metabolism and translation initiation. Several proteins within this pathway are valuable anticancer drug targets, among which several inhibitors of mTOR are now administered in routine practice. A better understanding of the structure and functions of PI3K has led to the development of novel inhibitors that have a more favorable toxicity profile as compared to the first generation of anti-PI3K drugs. In this article, we review the basics of PI3K biology and focus on its inhibitors, currently under investigation in clinical trials. The perspective for future directions in the setting of PI3K inhibition and novel trials is also discussed.
Inhibiting PI3K as a therapeutic strategy against cancer
Clinical and Translational Oncology, 2009
Class I PI3K is composed of heterodimeric lipid kinases regulating essential cellular functions including proliferation, apoptosis and metabolism. Class I PI3K isoforms are commonly amplifi ed in different cancer types and the PI3K catalytic subunit, PIK3CA, has been found mutated in a variable proportion of tumours of different origin. Furthermore, PI3K has been shown to mediate oncogenic signalling induced by several oncogenes such as HER2 or Ras. These facts suggest that PI3K might be a good target for anticancer drug discovery. Today, the rise of PI3K inhibitors and their fi rst in vivo results have cleared much of the path for the development of PI3K inhibitors for anticancer therapy. Here we will review the PI3K pathway and the pharmacological results of PI3K inhibition.
Challenges in the clinical development of PI3K inhibitors
Annals of the New York Academy of Sciences, 2013
The PI3K/Akt/mTOR pathway is one of the most frequently dysregulated signaling pathways in cancer and an important target for drug development. PI3K signaling plays a fundamental role in tumorigenesis, governing cell proliferation, survival, motility, and angiogenesis. Activation of the pathway is frequently observed in a variety of tumor types and can occur through several mechanisms. These mechanisms include (but are not limited to) upregulated signaling via the aberrant activation of receptors upstream of PI3K, amplification or gain-of-function mutations in the PIK3CA gene encoding the p110␣ catalytic subunit of PI3K, and inactivation of PTEN through mutation, deletion, or epigenetic silencing. PI3K pathway activation may occur as part of primary tumorigenesis, or as an adaptive response (via molecular alterations or increased phosphorylation of pathway components) that may lead to resistance to anticancer therapies. A range of PI3K inhibitors are being investigated for the treatment of different types of cancer; broad clinical development plans require a flexible yet well-structured approach to clinical trial design.
Cancer Discovery, 2019
The PI3K pathway is mutated and aberrantly activated in many cancers and plays a central role in tumor cell proliferation and survival, making it a rational therapeutic target. Until recently, however, results from clinical trials with PI3K inhibitors in solid tumors have been largely disappointing. Here, we describe several factors that have limited the success of these agents, including the weak driver oncogenic activity of mutant PI3K, suboptimal patient selection in trials, drug-related toxicities, feedback upregulation of compensatory mechanisms when PI3K is blocked, increased insulin production upon PI3Kα inhibition, lack of mutant-specific inhibitors, and a relative scarcity of studies using combinations with PI3K antagonists. We also suggest strategies to improve the impact of these agents in solid tumors. Despite these challenges, we are optimistic that isoform-specific PI3K inhibitors, particularly in combination with other agents, may be valuable in treating appropriately...
PI3K Inhibitors in Cancer: Clinical Implications and Adverse Effects
International Journal of Molecular Sciences
The phospatidylinositol-3 kinase (PI3K) pathway is a crucial intracellular signaling pathway which is mutated or amplified in a wide variety of cancers including breast, gastric, ovarian, colorectal, prostate, glioblastoma and endometrial cancers. PI3K signaling plays an important role in cancer cell survival, angiogenesis and metastasis, making it a promising therapeutic target. There are several ongoing and completed clinical trials involving PI3K inhibitors (pan, isoform-specific and dual PI3K/mTOR) with the goal to find efficient PI3K inhibitors that could overcome resistance to current therapies. This review focuses on the current landscape of various PI3K inhibitors either as monotherapy or in combination therapies and the treatment outcomes involved in various phases of clinical trials in different cancer types. There is a discussion of the drug-related toxicities, challenges associated with these PI3K inhibitors and the adverse events leading to treatment failure. In additio...
PI3K Pathway Inhibitors: Better Not Left Alone
The PI3K/Akt/mTOR signaling pathway plays a key role in diverse physiologic processes. It is also central to many aspects of the malignant process. Genetic phenomena that lead to constitutive pathway activation are common in human cancer; the most relevant are mutations affecting the catalytic subunit of PI3K and loss of function of the PTEN tumor suppressor. These factors have made this important cascade attractive as a potential target for cancer therapeutics. A host of inhibitors are now in various stages of development that target key nodes within the PI3K pathway. To date, however, the efficacy of these agents has fallen short of expectation, with at least one possible explanation being the presence of feedback loops and cross-talk that exists within and between PI3K and other signaling pathways. Accordingly, enthusiasm is again high as strategies employing therapeutic combinations are gaining pace, with encouraging results documented in both preclinical studies and emerging clinical trials. Here, we review the agents that have reached evaluation in early phase clinical studies of human subjects with cancer, and discuss the rationale for and use of novel drug combinations.