Specific inhibition of p110α subunit of PI3K: putative therapeutic strategy for KRAS mutant colorectal cancers

Cell line models for drug discovery in PIK3CA-mutated colorectal cancers

Colorectal cancer remains a major cause of cancer-related morbidity and mortality. Metastatic disease is still incurable in most cases. New therapies based on a better understanding of the pathogenesis are needed to improve outcomes. Mutations in the catalytic sub-unit of kinase PI3K encoded by gene PIK3CA are common in colorectal cancer cell lines and patient samples. The characteristics of colorectal cancer cell lines from the Cancer Cell Line Encyclopedia (CCLE), with and without PIK3CA mutations, were evaluated and compared. A panel of colorectal cancer cell lines with and without PIK3CA mutations were compared for their sensitivity to PIK3 inhibitors. Concomitant molecular abnormalities of sensitive versus resistant cell lines were identified. Colorectal cancer cell lines with PIK3CA mutations are commonly diploid and have microsatellite instability (MSI) and a high tumor mutation burden (TMB), compared with cell lines without PIK3CA mutations. Cell lines with PIK3CA mutations tend to have higher sensitivity to some but not all PI3K inhibitors tested and display variability in sensitivity. Both cell lines with MSI and microsatellite stable (MSS) are among the most sensitive to PI3K inhibitors. Multiple concomitant mutations in the PI3K/AKT and KRAS/BRAF/MEK/ERK pathways are often observed in sensitive cell lines. In concordance with patient samples, colorectal cancer cell lines with PIK3CA mutations display more commonly MSI and tend to be more sensitive to PI3K inhibitors. Variability in sensitivity of PIK3CA-mutated cell lines suggests that additional molecular abnormalities contribute to sensitivity.

The PI3K/Akt/mTOR axis in colorectal cancer: Oncogenic alterations, non-coding RNAs, therapeutic opportunities, and the emerging role of nanoparticles

Colorectal cancer (CRC) is one of the deadliest human malignancies worldwide. Several molecular pathways have been demonstrated to be involved in the initiation and development of CRC which among them, the overactivation of the phosphatidyl-inositol 3-kinase (PI3K)/Akt/mTOR axis is of importance. The current review aims to unravel the mechanisms by which the PI3K/Akt/mTOR pathway affects CRC progression; and also, to summarize the original data obtained from international research laboratories on the oncogenic alterations and polymorphisms affecting this pathway in CRC. Besides, we provide a special focus on the regulatory role of noncoding RNAs targeting the PI3K/Akt/mTOR pathway in this malignancy. Questions on how this axis is involved in the inhibition of apoptosis, in the induction of drug resistance, and the angiogenesis, epithelial to mesenchymal transition, and metastasis are also responded. We also discussed the PI3K/Akt pathway-associated prognostic and predictive biomarkers in CRC. In addition, we provide a general overview of PI3K/Akt/mTOR pathway inhibition whether by chemical-based drugs or by natural-based medications in the context of CRC, either as monotherapy or in combination with other therapeutic agents; however, those treatments might have life-threatening side effects and toxicities. To the best of our knowledge, the current review is one of the first ones highlighting the emerging roles of nanotechnology to overcome challenges related to CRC therapy in the hope that providing a promising platform for the treatment of CRC.

The modulation of PI3K/Akt pathway by 3β hydroxylup-12-en-28-oic acid isolated from Thymus linearis induces cell death in HCT-116 cells

The presence of intricate carbon skeletons in natural compounds enhances their bioactivity spectrum with unique modes of action at several targets in various dreadful diseases like cancer. The present study was designed to purify the molecules from Thymus linearis and elucidate their antiproliferative activity. The compounds were isolated from the active methanolic extract of Thymus linearis through column chromatography and characterized by various spectroscopic techniques. Antiproliferative activity of isolated compounds was evaluated using MTT assay on cancer and normal cell lines. Mechanism of cell death was elucidated using flow cytometric, microscopic, and Western blot analysis. Four compounds, Sitosterol, Chrysin, 3β-hydroxylup-12-en-28-oic acid (3BH), and β-Sitosterol glycoside, were isolated. Among these, 3BH was most potent antiproliferative agent across all cell lines under study, HCT-116 being the most affected one. 3BH was demonstrated to downregulate PI3Ksubunits (p110α and p85α), downstream pAktSer⁴⁷³ and prompted G₁ phase cell cycle arrest. The cell cycle CDK inhibitor p27 and p21 were upregulated with simultaneous downregulation of cyclin D1 and cyclin E in HCT-116 cells. This was accompanied by apoptosis, as depicted by decrease in Bcl-2/Bax ratio, with increase in active caspases-3 and caspase-9, cleavage of PARP-1, the generation of reactive oxygen species (ROS), and the loss of mitochondrial membrane potential. The findings established that 3BH induced cell death in HCT-116 cells by modulating PI3K/Akt signaling axis, impeding cell cycle, and instigating apoptosis.

Addressing cancer signal transduction pathways with antisense and siRNA oligonucleotides

Signal transduction pathways play key roles in the initiation, progression and dissemination of cancer. Thus, signaling molecules are attractive targets for cancer therapeutics and enormous efforts have gone into the development of small molecule inhibitors of these pathways. However, regrettably, there has been only moderate progress to date, primarily in connection with the RAS signaling pathway. Oligonucleotide-based drugs potentially offer several advantages for addressing signaling pathways, including their exquisite selectivity and their ability to exploit both enzymatic and nonenzymatic targets. Nonetheless, there are problems inherent in the oligonucleotide approach, not the least being the challenge of effectively delivering these complex molecules to intracellular sites within tumors. This survey article will provide a selective review of recent studies where oligonucleotides were used to address cancer signaling and will discuss both positive aspects and limitations of those studies. This will be set in the context of an overview of various cancer signaling pathways and small molecule approaches to regulate those pathways. The survey will also evaluate the challenges and opportunities implicit in the oligonucleotide-based approach to cancer signaling and will point out several possibilities for future research.

From basic researches to new achievements in therapeutic strategies of KRAS-driven cancers

Among the numerous oncogenes involved in human cancers, KRAS represents the most studied and best characterized cancer-related genes. Several therapeutic strategies targeting oncogenic KRAS (KRAS onc ) signaling pathways have been suggested, including the inhibition of synthetic lethal interactions, direct inhibition of KRAS onc itself, blockade of downstream KRAS onc effectors, prevention of post-translational KRAS onc modifications, inhibition of the induced stem cell-like program, targeting of metabolic peculiarities, stimulation of the immune system, inhibition of inflammation, blockade of upstream signaling pathways, targeted RNA replacement, and oncogene-induced senescence. Despite intensive and continuous efforts, KRAS onc remains an elusive target for cancer therapy. To highlight the progress to date, this review covers a collection of studies on therapeutic strategies for KRAS published from 1995 to date. An overview of the path of progress from earlier to more recent insights highlight novel opportunities for clinical development towards KRASonc-signaling targeted therapeutics.

PI3K: A Crucial Piece in the RAS Signaling Puzzle

RAS proteins are key signaling switches essential for control of proliferation, differentiation, and survival of eukaryotic cells. RAS proteins are mutated in 30% of human cancers. In addition, mutations in upstream or downstream signaling components also contribute to oncogenic activation of the pathway. RAS proteins exert their functions through activation of several signaling pathways and dissecting the contributions of these effectors in normal cells and in cancer is an ongoing challenge. In this review, we summarize our current knowledge about how RAS regulates type I phosphatidylinositol 3-kinase (PI3K), one of the main RAS effectors. RAS signaling through PI3K is necessary for normal lymphatic vasculature development and for RAS-induced transformation in vitro and in vivo, especially in lung cancer, where it is essential for tumor initiation and necessary for tumor maintenance.

Targeting the PI3K Signalling as a Therapeutic Strategy in Colorectal Cancer

Colorectal cancer (CRC) remains one of the leading causes of cancer mortality worldwide. Regarded as a heterogeneous disease, a number of biomarkers have been proposed to help in the stratification of CRC patients and to enable the selection of the best therapy for each patient towards personalized therapy. However, although the molecular mechanisms underlying the development of CRC have been elucidated, the therapeutic strategies available for these patients are still quite limited. Thus, over the last few years, a multitude of novel targets and therapeutic strategies have emerged focusing on deregulated molecules and pathways that are implicated in cell growth and survival. Particularly relevant in CRC are the activating mutations in the oncogene PIK3CA that frequently occur in concomitancy with KRAS and BRAF mutations and that lead to deregulation of the major signalling pathways PI3K and MAPK, downstream of EGFR. This review focus on the importance of the PI3K signalling in CRC development, on the current knowledge of PI3K inhibition as a therapeutic approach in CRC and on the implications PI3K signalling molecules may have as potential biomarkers and as new targets for directed therapies in CRC patients.

Pharmacogenomics of Targeted Agents for Personalization of Colorectal Cancer Treatment

The use of targeted agents in the treatment of metastatic colorectal cancer (CRC) has improved patient outcomes. Anti-epidermal growth factor receptor (anti-EGFR) agents (cetuximab and panitumumab) and antiangiogenic molecules (bevacizumab, regorafeninb, ramucirumab, and aflibercept) have been successfully integrated into clinical practice. Other drugs have been designed to target additional deregulated pathways in CRC, such as MAPK (mitogen-activated protein kinase)/PI3K-AKT (phosphatidylinositol-3-kinase-AKT serine/threonine kinase)/mTOR (mammalian target of rapamycin), HER-2 and 3 ( human epidermal growth factor receptor-2 and -3), and BRAF. A major issue with targeted treatment is early identification of patients with primary or secondary drug resistance. Pharmacogenomic research has demonstrated its value in this field, highlighting some tumor mutations that could discriminate responders from non-responders. The tumor genetic profile of the RAS/RAF pathway is needed before treatment with anti-EGFR agents; mutations in EGFR pathway genes have also been explored in relation to antiangiogenic molecules although further data are required prior to their integration into clinical practice. The introduction of immunotherapy has paved the way for a new generation of predictive markers, including genome-wide assessment of the tumor landscape. Furthermore, the development of next generation sequencing technology and non-invasive approaches to analyze circulating tumor DNA will make real-time monitoring of the tumor pharmacogenomic markers possible in the clinical routine, rendering precision medicine available to every patient.