Targeting the PI3K signaling pathway in KRAS mutant colon cancer

Selective PI3Kδ inhibitor TYM-3-98 suppresses AKT/mTOR/SREBP1-mediated lipogenesis and promotes ferroptosis in KRAS-mutant colorectal cancer

Colorectal cancer (CRC) is one of the most common tumors of the digestive system worldwide. KRAS mutations limit the use of anti-EGFR antibodies in combination with chemotherapy for the treatment of CRC. Therefore, novel targeted therapies are needed to overcome the KRAS-induced oncogenesis. Recent evidence suggests that inhibition of PI3K led to ferroptosis, a nonapoptotic cell death closely related to KRAS-mutant cells. Here, we showed that a selective PI3Kδ inhibitor TYM-3-98 can suppress the AKT/mTOR signaling and activate the ferroptosis pathway in KRAS-mutant CRC cells in a concentration-dependent manner. This was evidenced by the lipid peroxidation, iron accumulation, and depletion of GSH. Moreover, the overexpression of the sterol regulatory element-binding protein 1 (SREBP1), a downstream transcription factor regulating lipid metabolism, conferred CRC cells greater resistance to ferroptosis induced by TYM-3-98. In addition, the effect of TYM-3-98 was confirmed in a xenograft mouse model, which demonstrated significant tumor suppression without obvious hepatoxicity or renal toxicity. Taken together, our work demonstrated that the induction of ferroptosis contributed to the PI3Kδ inhibitor-induced cell death via the suppression of AKT/mTOR/SREBP1-mediated lipogenesis, thus displaying a promising therapeutic effect of TYM-3-98 in CRC treatment.

The effect of novel nitrogen-based chalcone analogs on colorectal cancer cells: Insight into the molecular pathways

In colorectal cancer (CRC), aberrations in KRAS are associated with aggressive tumorigenesis and an overall low survival rate because of chemoresistance and adverse effects. Ergo, complementary, and integrative medicines are being considered for CRC treatment. Among which is the use of natural chalcones that are known to exhibit anti-tumor activities in KRAS mutant CRC subtypes treatment regimens. Consequently, we examine the effect of two novel compounds (DK13 and DK14) having chalcones with nitrogen mustard moiety on CRC cell lines (HCT-116 and LoVo) with KRAS mutation. These compounds were synthesized in our lab and previously reported to exhibit potent activity against breast cancer cells. Our data revealed that DK13 and DK14 treatment suppress cell growth, disturb the progression of cell cycle, and trigger apoptosis in CRC cell lines. Besides, treatment with both compounds impedes cell invasion and colony formation in both cell lines as compared to 5-FU; this is accompanied by up and down regulations of E-cadherin and Vimentin, respectively. At the molecular level, both compounds deregulate the expression and phosphorylation of β-catenin, Akt and mTOR, which are the main likely molecular mechanisms underlying these biological occurrences. Our findings present DK13 and DK14 as novel chemotherapies against CRC, through β-catenin/Akt/mTOR signaling pathways.

Targeted nanodelivery of siRNA against KRAS G12D inhibits pancreatic cancer

Pancreatic cancer (PC) stands as a most deadly malignancy due to few effective treatments in the clinics. KRAS G12D mutation is a major driver for most PC cases, and silencing of KRAS G12D is considered as a potential therapeutic strategy for PC, which is nevertheless crippled by lacking a pragmatic delivery system for siRNA against KRAS G12D (siKRAS). Here, we report that cRGD peptide-modified bioresponsive chimaeric polymersomes (cRGD-BCP) mediate highly efficient siKRAS delivery to PANC-1 tumor, potently silencing KRAS G12D mRNA in tumor cells and effectively suppressing PC tumor growth in mice. cRGD-BCP exhibited remarkable encapsulation of siKRAS (loading content > 14 wt.%, loading efficiency > 90%) to form stable and uniform (ca. 68 nm) nanovesicles (cRGD-BCP-siKRAS). Of note, cRGD density greatly impacted the cellular uptake and silencing efficiency of cRGD-BCP-siKRAS in PANC-1 cells, in which an optimal cRGD density of 15.7 mol.% achieved 3.7- and 3.6-fold enhancement of internalization and gene silencing, respectively, compared with non-targeted BCP-siKRAS. cRGD-BCP-siKRAS was practically intact after 3-week storage at 4°C. Intriguingly, cRGD-BCP-siKRAS markedly enhanced the uptake of siKRAS in PANC-1 tumor, and at a siKRAS dose of 3 mg/kg knocked down 90% KRAS G12D gene, resulting in potent tumor inhibition and extraordinary survival benefits (median survival time: 101 days versus 38 (PBS group) and 59 days (BCP-siKRAS)) with 40% mice achieved complete regression. It appears that cRGD-mediated nanodelivery of siKRAS provides a potential cure for pancreatic cancer. STATEMENT OF SIGNIFICANCE: Small interfering RNA (siRNA) emerges as a specific and powerful biopharmaceuticals against cancers; however, inefficient in vivo delivery impedes its clinical translation. In spite of the fact that KRAS G12D mutation has been identified as a major driver for most pancreatic cancer, its notorious non-druggability renders little success on development of molecular targeted drugs. Pancreatic cancer is deemed as current king-of-cancer. Here, we show that cyclic RGD peptide installed bioresponsive polymersomes are able to efficiently deliver siRNA against KRAS G12D to pancreatic tumor, resulting in 90% gene knock-down and effective tumor inhibition. Strikingly, two out of five mice have been cured. This targeted nanodelivery of siRNA provides a high-efficacy treatment strategy for pancreatic cancer.

Lymphatic disorders caused by mosaic, activating KRAS variants respond to MEK inhibition

Central conducting lymphatic anomaly (CCLA) due to congenital maldevelopment of the lymphatics can result in debilitating and life-threatening disease with limited treatment options. We identified 4 individuals with CCLA, lymphedema, and microcystic lymphatic malformation due to pathogenic, mosaic variants in KRAS. To determine the functional impact of these variants and identify a targeted therapy for these individuals, we used primary human dermal lymphatic endothelial cells (HDLECs) and zebrafish larvae to model the lymphatic dysplasia. Expression of the p.Gly12Asp and p.Gly13Asp variants in HDLECs in a 2‑dimensional (2D) model and 3D organoid model led to increased ERK phosphorylation, demonstrating these variants activate the RAS/MAPK pathway. Expression of activating KRAS variants in the venous and lymphatic endothelium in zebrafish resulted in lymphatic dysplasia and edema similar to the individuals in the study. Treatment with MEK inhibition significantly reduced the phenotypes in both the organoid and the zebrafish model systems. In conclusion, we present the molecular characterization of the observed lymphatic anomalies due to pathogenic, somatic, activating KRAS variants in humans. Our preclinical studies suggest that MEK inhibition should be studied in future clinical trials for CCLA due to activating KRAS pathogenic variants.

The potential effect of Schisandrin-B combination with panitumumab in wild-type and mutant colorectal cancer cell lines: Role of apoptosis and autophagy

Panitumumab is an approved monoclonal antibody for the treatment of colorectal cancer (CRC); however, mutations in EGFR signaling pathway resulted in poor response. Schisandrin-B (Sch-B) is a phytochemical that was suggested to protect against inflammation, oxidative stress, and cell proliferation. The present study aimed to investigate the potential effect of Sch-B on panitumumab-induced cytotoxicity in wild-type Caco-2, and mutant HCT-116 and HT-29 CRC cell lines, and the possible underlying mechanisms. CRC cell lines were treated with panitumumab, Sch-B, and their combination. The cytotoxic effect of drugs was determined by MTT assay. The apoptotic potential was assessed in-vitro by DNA fragmentation and caspase-3 activity. Additionally, autophagy was investigated via microscopic detection of autophagosomes and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) measurement of Beclin-1, Rubicon, LC3-II, and Bcl-2 expression. The drug pair enhanced panitumumab cytotoxicity in all CRC cell lines where IC50 of panitumumab was decreased in Caco-2 cell line. Apoptosis was induced through caspase-3 activation, DNA fragmentation, and Bcl-2 downregulation. Caco-2 cell line treated with panitumumab showed stained acidic vesicular organelles, contrariwise, all cell lines treated with Sch-B or the drug pair displayed green fluorescence indicating the lack of autophagosomes. qRT-PCR revealed the downregulation of LC3-II in all CRC cell lines, Rubicon in mutant cell lines, and Beclin-1 in HT-29 cell line only. Sch-B at 6.5 µM promoted panitumumab-induced apoptotic cell death, in-vitro, via caspase-3 activation and Bcl-2 downregulation, rather than autophagic cell death. This novel combination therapy against CRC, allows the reduction of panitumumab dose to guard against its adverse effects.

Therapeutic implications and clinical manifestations of thymoquinone

Thymoquinone (TQ), a natural phytochemical predominantly found in Nigella sativa, has been investigated for its numerous health benefits. TQ showed anti-cancer, anti-oxidant, and anti-inflammatory properties, validated in various disease models. The anti-cancer potential of TQ is goverened by anti-proliferation, cell cycle arrest, apoptosis induction, ROS production, anti-metastasis and anti-angiogenesis, inhibition of cell migration and invasion action. Additionally, TQ exhibited antitumor activity via the modulation of multiple pathways and molecular targets, including Akt, ERK1/2, STAT3, and NF-κB. The present review highlighted the anticancer potential of TQ . We summarize the anti-cancer, anti-oxidant, and anti-inflammatory properties of TQ, focusing on its molecular targets and its promising action in cancer therapy. We further described the molecular mechanisms by which TQ prevents signaling pathways that mediate cancer progression, invasion, and metastasis.

Bevacizumab and anexelekto inhibitor, TP-0903 inhibits TGF-β1-induced epithelial-mesenchymal transition of colon cancer cells

The incidence of colorectal cancer (CRC) is reported to be increasing nowadays, with a large proportion of newly diagnosed CRC patients being affected by metastasis. Epithelial-mesenchymal transition (EMT) is an important event in the development of metastasis of CRC. In this study, we investigated whether the anticancer drug bevacizumab and anexelekto inhibitor, TP-0903, regulate EMT of colon cancer cells induced by transforming growth factor-beta 1 (TGF-β1). Using quantitative real-time PCR and western blot analysis, we found that bevacizumab and TP-0903 decreased the expression levels of fibronectin, alpha-smooth muscle actin, and vimentin, whereas they restored E-cadherin expression in TGF-β1-exposed SW480 and HCT116 cells. In addition, we elucidated that bevacizumab and TP-0903 inhibited the migration and invasion of TGF-β1-exposed colon cancer cells using scratched wound healing, transwell migration, and Matrigel-coated invasion assays. Finally, we discovered that bevacizumab and TP-0903 inactivated the Smad 2/3 signaling pathway in TGF-β1-exposed SW480 and HCT116 cells. Therefore, we suggest that treatment of bevacizumab and TP-0903 inhibits TGF-β1-induced EMT of colon cancer cells through inactivation of the Smad 2/3 signaling pathway.

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.

New drugs for the treatment of metastatic colorectal cancer

Colorectal cancer (CRC) represents one of the most frequent malignancies in terms of incidence and mortality, thus representing the third leading cause of cancer death worldwide. In the last decade, few drugs have enriched the treatment landscape of metastatic CRC and have significantly affected prognosis. Unlike other neoplasms, metastatic CRC patients who have exhausted treatment options often still maintain a good performance status. There are many challenges to increasing potential treatment options, notably a better understanding of disease biology and the mechanisms of resistance underlying cancer treatment failure. The development of new drugs for metastatic CRC certainly represents one of the most important challenges in medical oncology. This article discusses the main limitations in the development of new drugs and potential future scenarios. In particular, we addressed three questions: (1) The main limitations of targeted therapy in the treatment of metastatic CRC (mCRC); (2) New target armamentarium that could escape primary and secondary resistance and lead to more personalized mCRC therapy; and (3) Future directions.

Resistance to anti-EGFR therapies in metastatic colorectal cancer: underlying mechanisms and reversal strategies

Cetuximab and panitumumab are monoclonal antibodies (mAbs) against epidermal growth factor receptor (EGFR) that are effective agents for metastatic colorectal cancer (mCRC). Cetuximab can prolong survival by 8.2 months in RAS wild-type (WT) mCRC patients. Unfortunately, resistance to targeted therapy impairs clinical use and efficiency. The mechanisms of resistance refer to intrinsic and extrinsic alterations of tumours. Multiple therapeutic strategies have been investigated extensively to overcome resistance to anti-EGFR mAbs. The intrinsic mechanisms include EGFR ligand overexpression, EGFR alteration, RAS/RAF/PI3K gene mutations, ERBB2/MET/IGF-1R activation, metabolic remodelling, microsatellite instability and autophagy. For intrinsic mechanisms, therapies mainly cover the following: new EGFR-targeted inhibitors, a combination of multitargeted inhibitors, and metabolic regulators. In addition, new cytotoxic drugs and small molecule compounds increase the efficiency of cetuximab. Extrinsic alterations mainly disrupt the tumour microenvironment, specifically immune cells, cancer-associated fibroblasts (CAFs) and angiogenesis. The directions include the modification or activation of immune cells and suppression of CAFs and anti-VEGFR agents. In this review, we focus on the mechanisms of resistance to anti-EGFR monoclonal antibodies (anti-EGFR mAbs) and discuss diverse approaches to reverse resistance to this therapy in hopes of identifying more mCRC treatment possibilities.

Preparation of a novel EGFR specific immunotoxin and its efficacy of anti-colorectal cancer in vitro and in vivo

OBJECTIVES

Epithelial growth factor receptor (EGFR), as a malignancy marker, is overly expressed in multiple solid tumors including colorectal neoplasms, one of the most prevalent malignancies worldwide. The main objective of this study is to enhance the efficacy of anti-tumor therapy targeting EGFR by constructing a novel EGFR-specific immunotoxin (C-CUS_245C) based on Cetuximab and recombinant Cucurmosin (CUS_245C).

METHODS

E. coli BL21 (DE3) PlysS (E. coli) was used to express CUS_245C with a cysteine residue inserting to the C-terminus of Cucurmosin. Then immobilized metal ion affinity chromatography (IMAC) was used to purify CUS_245C. The chemical conjugation method was used for the preparation of C-CUS_245C. Then dialysis and IMAC were used to purify C-CUS_245C. Western blot as well as SDS-PAGE was carried out to characterize the formation of C-CUS_245C. At last the anti-colorectal cancer activity of C-CUS_245C was investigated in vitro and in vivo.

RESULTS

CUS_245C with high purity could be obtained from the prokaryotic system. C-CUS_245C was successfully constructed and highly purified. The cytotoxicity assays in vitro showed a significant proliferation inhibition of C-CUS_245C on EGFR-positive cells for 120 h with IC₅₀ values less than 0.1 pM. Besides, the anti-tumor efficacy of C-CUS_245C was remarkably more potent than that of Cetuximab, CUS_245C, and C + CUS_245C (P < 0.001). Whereas the cytotoxicity of C-CUS_245C could hardly be detected on EGFR-null cell line. Our results also showed that C-CUS_245C had efficacy of anti-colorectal cancer in mouse xenograft model, indicating the therapeutic potential of C-CUS_245C for the targeted therapy of colorectal neoplasms.

CONCLUSIONS

C-CUS_245C exhibits potent and EGFR-specific cytotoxicity. Insertional mutagenesis technique is worthy to be adopted in the preparation of immunotoxin. Immunotoxin can be highly purified through dialysis followed by IMAC.

CoA Synthase (COASY) Mediates Radiation Resistance via PI3K Signaling in Rectal Cancer

Neoadjuvant radiation is standard of care for locally advanced rectal cancer. Response to radiation is highly variable and directly linked with survival. However, there currently are no validated biomarkers or molecular targets to predict or improve radiation response, which would help develop personalized treatment and ideally targeted therapies. Here, we identified a novel biomarker, coenzyme A synthase (COASY), whose mRNA expression was consistently elevated in radioresistant human rectal cancers. This observation was validated in independent patient cohorts and further confirmed in colorectal cancer cell lines. Importantly, genetic overexpression and knockdown yielded radioresistant and sensitive phenotypes, respectively, in vitro and in vivo. COASY-knockdown xenografts were more vulnerable to radiation, showing delayed tumor growth, decreased proliferation, and increased apoptosis. Mechanistically, COASY protein directly interacted with the PI3K regulatory subunit PI3K-P85α, which increased AKT and mTOR phosphorylation, enhancing cell survival. Furthermore, shRNA COASY knockdown disrupted downstream PI3K pathway activation and also hindered DNA double-strand break repair, which both led to improved radiosensitivity. Collectively, this work reveals for the first time the biological relevance of COASY as a predictive rectal cancer biomarker for radiation response and offers mechanistic evidence to support COASY as a potential therapeutic target. SIGNIFICANCE: COASY is a novel radiotherapy response modulator in rectal cancer that regulates PI3K activation and DNA repair. Furthermore, COASY levels directly correlate with radiation response and serve as a predictive biomarker.

Phenotypic characterization of the novel, non-hotspot oncogenic KRAS mutants E31D and E63K

KRAS proto-oncogene, GTPase (KRAS) functions as a molecular switch at the apex of multiple signaling pathways controlling cell proliferation, differentiation, migration, and survival. Canonical KRAS mutants, such as those in codons 12 and 13, produce constitutively active oncoproteins that short-circuit epidermal growth factor receptor (EGFR)-initiated signaling, resulting in dysregulated downstream effectors associated with cellular transformation. Therefore, anti-EGFR therapy provides little to no clinical benefit to patients with activating KRAS mutations. Current genotyping procedures based on canonical mutation detection only account for ~40% of non-responders, highlighting the need to identify additional predictive biomarkers. In the present study, two novel non-hotspot KRAS mutations were functionally characterized in vitro: KRAS E31D was identified from a genetic screen of colorectal cancer specimens at the UP-National Institutes of Health. KRAS E63K is curated in the Catalogue of Somatic Mutations in Cancer database. Similar to the canonical mutants KRAS G12D and KRAS G13D, NIH3T3 cells overexpressing KRAS E31D and KRAS E63K showed altered morphology and were characteristically smaller, rounder, and highly refractile compared with their non-transformed counterparts. Filamentous actin staining also indicated cytoplasmic shrinkage, membrane ruffling, and formation of pseudopod protrusions. Further, they displayed higher proliferative rates and higher migratory rates in scratch wound assays compared with negative controls. These empirical findings suggest the activating impact of the novel KRAS mutations, which may contribute to resistance to anti-EGFR therapy. Complementary studies to elucidate the molecular mechanisms underlying the transforming effect of the rare mutants are required. In parallel, their oncogenic capacity in vivo should also be investigated.

Knockdown long noncoding RNA nuclear paraspeckle assembly transcript 1 suppresses colorectal cancer through modulating miR-193a-3p/KRAS

The nuclear paraspeckle assembly transcript 1 (abbreviated as NEAT1), a nuclear sufficient long noncoding RNA (abbreviated as lncRNA), has aroused a rising concern in recent years. As uncovered by reports, the increase in NEAT1 is related to the deteriorated prognosis of lung cancer, breast cancer, hepatocellular cancer, and colorectal cancer (abbreviated as CRC). Thus far, the mechanism of NEAT1 has not been elucidated by the existing researches. The impact of knockdown of both NEAT1 and its predicted downstream miR‐193a‐3p in CRC cells was examined here to delve into their interactions and mechanisms. Additionally, the target of miR‐193a‐3p, Kirsten rat sarcoma viral oncogene homolog (abbreviated as KRAS), was also predicted by bioinformatics algorithms. Small interfering RNA and antisense oligonucleotides that inhibit NEAT1, as well as overexpression or knockdown of miR‐193a‐3p, were adequately drawn upon to confirm that NEAT1 serves as a miR‐193a‐3p sponge or competing endogenous RNA, to impact miR‐193a‐3p's further functions, including modulating KRAS proteins, both in vitro and in vivo. Generally, lncRNA NEAT1/hsa‐miR‐193a‐3p/KRAS axis was substantiated in CRC cells and could provide novel insight into both diagnostic and therapeutic advancement in CRC.

Mediatory role of BLT2 in the proliferation of KRAS mutant colorectal cancer cells

Inflammatory lipid mediators play various roles in colorectal cancer progression through complex pathways. However, the mechanism by which lipoxygenase-derived inflammatory lipid mediators contribute to colorectal cancer progression remains elusive. In this study, we found that BLT2, a cell surface GPCR for leukotriene B₄ and 12‑hydroxyeicosatetraenoic acid, is highly upregulated in KRAS mutant LOVO and SW480 colorectal cancer cells and plays critical roles in mediating proliferation through activation of phosphatidylinositol 3‑kinase (PI3K)/protein kinase B (Akt) and subsequent upregulation of cyclin D1. Exposure to BLT2 siRNA or LY255283, a specific BLT2 inhibitor, clearly suppressed the proliferation of KRAS mutant colorectal cancer cells and markedly increased cell cycle arrest by downregulating the PI3K/Akt-cyclin D1 cascade. Xenograft tumor formation by LOVO and SW480 cells in athymic mice was also substantially reduced by treatment with the BLT2 inhibitor in vivo. Together, our study demonstrates that BLT2 is necessary for the proliferation of LOVO and SW480 cells and thus may be a potential therapeutic target for the treatment of KRAS mutant colorectal cancer.

Activation of WNT/β-catenin signaling results in resistance to a dual PI3K/mTOR inhibitor in colorectal cancer cells harboring PIK3CA mutations

PIK3CA is a frequently mutated gene in cancer, including about ~15 to 20% of colorectal cancers (CRC). PIK3CA mutations lead to activation of the PI3K/AKT/mTOR signaling pathway, which plays pivotal roles in tumorigenesis. Here, we investigated the mechanism of resistance of PIK3CA-mutant CRC cell lines to gedatolisib, a dual PI3K/mTOR inhibitor. Out of a panel of 29 CRC cell lines, we identified 7 harboring one or more PIK3CA mutations; of these, 5 and 2 were found to be sensitive and resistant to gedatolisib, respectively. Both of the gedatolisib-resistant cell lines expressed high levels of active glycogen synthase kinase 3-beta (GSK3β) and harbored the same frameshift mutation (c.465_466insC; H155fs*) in TCF7, which encodes a positive transcriptional regulator of the WNT/β-catenin signaling pathway. Inhibition of GSK3β activity in gedatolisib-resistant cells by siRNA-mediated knockdown or treatment with a GSK3β-specific inhibitor effectively reduced the activity of molecules downstream of mTOR and also decreased signaling through the WNT/β-catenin pathway. Notably, GSK3β inhibition rendered the resistant cell lines sensitive to gedatolisib cytotoxicity, both in vitro and in a mouse xenograft model. Taken together, these data demonstrate that aberrant regulation of WNT/β-catenin signaling and active GSK3β induced by the TCF7 frameshift mutation cause resistance to the dual PI3K/mTOR inhibitor gedatolisib. Cotreatment with GSK3β inhibitors may be a strategy to overcome the resistance of PIK3CA- and TCF7-mutant CRC to PI3K/mTOR-targeted therapies.

The Nrf2 inhibitor brusatol is a potent antitumour agent in an orthotopic mouse model of colorectal cancer

Nrf2 is a transcription factor that regulates cellular stress response and irinotecan-metabolising pathways. Its aberrant activity has been reported in a number of cancers, although relatively few studies have explored a role for Nrf2 in colorectal cancer (CRC). This study assessed the expression of Nrf2 in patient CRC tissues and explored the effect of Nrf2 modulation alone, or in combination with irinotecan, in human (HCT116) and murine (CT26) cell lines in vitro and in an orthotopic syngeneic mouse model utilising bioluminescent imaging. Using a tissue microarray, Nrf2 was found to be overexpressed (p<0.01) in primary CRC and metastatic tissue relative to normal colon, with a positive correlation between Nrf2 expression in matched primary and metastatic samples. In vitro experiments in CRC cell lines revealed that Nrf2 siRNA and brusatol, which is known to inhibit Nrf2, decreased viability and sensitised cells to irinotecan toxicity. Furthermore, brusatol effectively abrogated CRC tumour growth in subcutaneously and orthotopically-allografted mice, resulting in an average 8-fold reduction in luminescence at the study end-point (p=0.02). Our results highlight Nrf2 as a promising drug target in the treatment of CRC.

Biomarker-driven and molecular targeted therapies for colorectal cancers

Improved clinical selection and identification of new molecules and innovative strategies have widened treatment options and increased overall survival in metastatic colorectal cancer patients in recent years. Biomarker-driven therapies represent an emerging issue in this field and new targeted treatments are under investigation and probably will be soon adopted into daily clinical practice. In the present review, the role RAS, BRAF mutations, Her2 amplification, microsatellite instability, and CpG island methylator phenotype are discussed according to their possible roles as prognostic, predictive markers, as well as possible biomarker-driven treatment options.

Colorectal cancer spheroid biobanks: multi-level approaches to drug sensitivity studies

Biobanking of molecularly characterized colorectal cancer stem cells (CSCs) generated from individual patients and growing as spheroids in defined serum-free media offer a fast, feasible, and multi-level approach for the screening of targeted therapies and drug resistance molecular studies. By combining in vitro and in vivo analyses of cetuximab efficacy with genetic data on an ongoing collection of stem cell-enriched spheroids, we describe the identification and preliminary characterization of microsatellite stable (MSS) CSCs that, despite the presence of the KRAS (G12D) mutation, display epidermal growth factor (EGF)-dependent growth and are strongly inhibited by anti-EGF-receptor (EGFR) treatment. In parallel, we detected an increased resistance to anti-EGFR therapy of microsatellite instable (MSI) CSC lines irrespective of KRAS mutational status. MSI CSC lines carried mutations in genes coding for proteins with a role in RAS and calcium signaling, highlighting the role of a genomically unstable context in determining anti-EGFR resistance. Altogether, these results argue for a multifactorial origin of anti-EGFR resistance that emerges as the effect of multiple events targeting direct and indirect regulators of the EGFR pathway. An improved understanding of key molecular determinants of sensitivity/resistance to EGFR inhibition will be instrumental to optimize the clinical efficacy of anti-EGFR agents, representing a further step towards personalized treatments.

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.

Combination of cecropinXJ and LY294002 induces synergistic cytotoxicity, and apoptosis in human gastric cancer cells via inhibition of the PI3K/Akt signaling pathway

The aim of the present study was to investigate the cytotoxic and apoptotic effects of cecropinXJ against human gastric cancer BGC823 cells, either alone, or in combination with a specific phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002. Cell viability and the apoptosis rate were measured using flow cytometry with Annexin-V staining. Additionally, the expression levels of several RAC-α serine/threonine kinase (Akt) phosphorylation-associated proteins and apoptosis-regulating proteins were evaluated by western blot analysis. It was observed that the combination of cecropinXJ and LY294002 resulted in significant synergistic cytotoxic and apoptosis effects, as compared with any single agent alone, in a dose-dependent manner. Corresponding to enhanced apoptosis, the expression levels of certain apoptosis-regulating proteins were changed, the most notable being the upregulation of caspase-3, B-cell lymphoma-2 (Bcl-2)-associated death promotor, Bcl-2 homologous antagonist killer, Bcl-2 interacting killer, Bcl-2-like protein 11, Bcl-2-like protein 4 and cytochrome c, and the downregulation of phosphorylated-Bad and Bcl-2 proteins. The present study provided a novel therapeutic regimen for the use of the cecropinXJ in combination with LY294002 for the treatment of gastric cancer.

The HSP90 inhibitor, NVP-AUY922, attenuates intrinsic PI3K inhibitor resistance in KRAS-mutant non-small cell lung cancer

More than 25% of non-small cell lung cancers (NSCLCs) carry mutations in KRAS, one of the most common oncogenic drivers in this disease. KRAS-mutant NSCLC responds poorly to currently available therapies; therefore, novel treatment strategies are needed. Here, we describe a particularly promising targeted therapeutic strategy against KRAS mutation-harboring NSCLC intrinsically resistant to treatment by PI3K inhibition. We found that intrinsic resistance to PI3K inhibition derived from RAF/MEK/ERK and RSK activation, bypassing blockage of the PI3K/AKT/mTOR pathway. The HSP90 inhibitor AUY922 suppressed both PI3K/AKT/mTOR and RAF/MEK/ERK signaling, rendering cells sensitive to a PI3K inhibitor (omipalisib, GSK458). Combining these two drugs achieved a synergistic effect, even using only sub-therapeutic concentrations. Dual inhibition of the HSP90 and PI3K signaling pathways with sub-therapeutic doses of these combined anticancer drugs may represent a potent treatment strategy for KRAS-mutant NSCLC with intrinsic resistance to PI3K inhibition.

Exendin-4 does not modify growth or apoptosis of human colon cancer cells

AIM

Glucagon-like peptide-1 (GLP-1) receptor agonists are a kind of very popular antidiabetes drugs. They promote cell proliferation and survival through activation of signaling pathways in human islet cells involving phosphate idylinositol 3 kinase (PI3K) and extracellular regulated kinases 1 and 2 (ERK1/2), which are frequently activated in human colon cancer cells. Then, it is possible that taking GLP-1 receptor (GLP-1R) agonists persistently would induce proliferation of β cells as well as colon cancer cells. So, clarifying the effects and mechanisms of GLP-1R agonists on colon cancer cells has important clinical implications.

MATERIALS AND METHODS

We investigated GLP-1R expression in human colon cancer tissue samples with immunohistochemisty analysis and explored the effects of exendin-4, a GLP-1 receptor agonist, on colon cancer cells in vitro and in vivo.

RESULTS

The results showed lack of GLP-1R expression in both human colon cancer tissues and colon cancer cell lines. Exendin-4 did not enhance the proliferation and migration of colon cancer cell lines in vitro, and nor did it inhibit apoptosis induced by cytotoxic agents such as 5-fluorouracil (5-FU) or irinotecan. In addition, exendin-4 did not promote the propagation of colon cancer cells in vivo.

CONCLUSION

Our study suggests that GLP-1R agonists do not modify the growth or survival of human colon cancer cells and may be safe for diabetic patients with colon cancer.

FasR and FasL in colorectal cancer

Colorectal cancer (CRC) is one of the most common solid organ cancers prevalent worldwide causing, in spite of advancing therapeutic methodology, high rate of patient mortality, especially due to metastasis development. The cancer stem cell (CSC) theory of tumor growth indicates that CSCs within the tumor mass have great capacity to initiate and sustain tumor growth. Following the suggestion that Fas signaling can be engaged in apoptosis, tumor maintenance, senescence or DICE (death induced by CD95 or CD95L elimination), the attempts to broaden the knowledge concerning the relationships between CSCs features and FasR/FasL appeared to be necessary. The most important advantage of our study was the simultaneously analysis of CSCs from commonly used CRC lines (HCT116 and HT29) and tumor fragments collected from CRC patients. Moreover, the sphere-promoting expansion of CRC lines brought a specific three-dimensional specific environment for CSC exploration. We further investigated the function of Fas signaling in CRC lines depending on the culture mode as we incubated HCT116 and HT29 cells with anti-FasR agonistic antibodies. It appeared to act in a line-dependent and culture mode-dependent manner and influenced some particular features of CSCs such as spherogenicity, proliferation and phenotype. Additionally, the analysis of mRNA level showed that disease progression is associated with significantly increased expression of FasR and/or FasL. In conclusion, our observation seems to confirm that spherical model of cancer lines is more reliable for some sophisticated analysis because of their greater resemblance to the CSCs from human CRC samples in comparison to commonly used adherent cells, at least according to aspects of their biology analyzed in this study. That can be extended to the resemblance of in vitro sphere forming conditions to the in vivo environment. However, the greatest difference concerns the level of apoptosis, thus, this issue require further experiments.

Telomere length regulation through epidermal growth factor receptor signaling in cancer

Length of the telomere (TL), a structure at the tip of chromosome that protects and ensures stability, is determined by multi-protein complexes such as telosome/shelterin and telomerase. Earlier studies from our laboratory show that longer TL has potential to be positive predictive biomarker of clinical outcome to anti-epidermal growth factor receptor (EGFR) monoclonal antibody therapy in patients with KRAS WT metastatic colorectal cancer. Although there is extensive literature suggesting the role of shelterin and telomerase, not much literature exists that describes the role of EGFR and KRAS pathway in regulating TL. This detailed review focuses on an insight into various components, including proteins, enzymes and transcription factors, interlinking between EGFR pathways and telomerase that regulate TL.

A Novel Combination Treatment Targeting BCL-XL and MCL1 for KRAS/BRAF-mutated and BCL2L1-amplified Colorectal Cancers

Colorectal cancer is the third most commonly diagnosed cancer in the world, and exhibits heterogeneous characteristics in terms of genomic alterations, expression signature, and drug responsiveness. Although there have been considerable efforts to classify this disease based on high-throughput sequencing techniques, targeted treatments for specific subgroups have been limited. KRAS and BRAF mutations are prevalent genetic alterations in colorectal cancers, and patients with mutations in either of these genes have a worse prognosis and are resistant to anti-EGFR treatments. In this study, we have found that a subgroup of colorectal cancers, defined by having either KRAS or BRAF (KRAS/BRAF) mutations and BCL2L1 (encoding BCL-X_L) amplification, can be effectively targeted by simultaneous inhibition of BCL-X_L (with ABT-263) and MCL1 (with YM-155). This combination treatment of ABT-263 and YM-155 was shown to have a synergistic effect in vitro as well as in in vivo patient-derived xenograft models. Our data suggest that combined inhibition of BCL-X_L and MCL1 provides a promising treatment strategy for this genomically defined colorectal cancer subgroup. Mol Cancer Ther; 16(10); 2178-90. ©2017 AACR.

The identification and validation of Trichosstatin A as a potential inhibitor of colon tumorigenesis and colon cancer stem-like cells

Colon cancer is one of the most prevalent cancer types in developed countries. Metastasis and drug resistance are two contributing factors to the high mortality rate. Accumulating evidence suggest that cancer stem-like cells (CSCs) represents as a major contributor to these malignant features. Here, we identified and isolated colon cancer stem-like cells using side-population (SP) method from human colon cancer cell lines. SP colon cells demonstrate cancer stem-like cell properties including enhanced sphere-forming ability and resistance towards fluorouracil (5-FU). The CSC properties were associated with the increased expression level of major oncogenic and stem cell markers including β-catenin, NF-kB, Akt/mTOR, KRAS and c-Myc. Trichostatin A (TSA), an antifungal antibiotic also a HDAC inhibitor, was found to function not only to decrease the expression of oncogenic markers but also the colon CSC properties. Importantly, TSA and 5-FU combined treatment synergistically suppressed colon cancer viability. Finally, in vivo results demonstrated that TSA alone and in combination with 5-FU effectively suppressed colon tumorigenesis. Collectively, this study provides preclinical evidence that TSA may function as a potential colon cancer therapeutic agent by targeting CSC and overcoming 5-FU resistance.

Deregulation of the miR-16-KRAS axis promotes colorectal cancer

KRAS plays a significant role in the etiology and progression of colorectal cancer (CRC), but the mechanism underlying this process has not been fully elucidated. In this study, we found that the KRAS protein levels were higher in CRC tissues than in the normal adjacent tissues, whereas its mRNA levels varied irregularly, suggesting that a post-transcriptional mechanism is involved in the regulation of KRAS. Then, we performed bioinformatic analyses to search for miRNAs that potentially target KRAS. We predicted and experimentally validated that miR-16 directly recognizes the 3'-UTR of the KRAS transcript and regulates KRAS expression. Furthermore, the in vitro results showed that the repression of KRAS by miR-16 suppressed the proliferation and invasion and induced the apoptosis of CRC cells, and the in vivo results revealed that miR-16 exerted a tumor-suppressive effect by negatively regulating KRAS in xenograft mice. Taken together, our findings provide evidence supporting the role of miR-16 as a tumor suppressor in CRC by targeting KRAS.

Novel therapeutics in metastatic colorectal cancer: molecular insights and pharmacogenomic implications

Although the survival of metastatic colorectal cancer (mCRC) patients has improved five-fold over the last century, CRC remains a significant global health burden. Impressive strides have been made in identifying new regimens, employing maintenance strategies to limit treatment toxicities, and combining multidisciplinary approaches to achieve cure in oligometastatic disease. Attempts at personalized integration of targeted agents have been limited by the ability to identify molecularly enriched patient populations most likely to benefit. In this review, we discuss novel therapeutics and regimens recently approved and in development for mCRC. In addition, we discuss using older agents in novel combination and maintenance strategies, and highlight evidence for implementing pharmacogenomic data and non-invasive monitoring into the personalized management of mCRC patients.

Targeting the PI3K signaling pathway in KRAS mutant colon cancer

Metastatic colorectal cancer (CRC) patients with v‐Ki‐ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations are resistant to monoclonal antibody that targets the epidermal growth factor receptor such as cetuximab. BKM120 targets phosphatidylinositide‐3‐kinase (PIK3CA), but it is unknown whether BKM120 can reverse cetuximab resistance in KRAS mutant CRC. Human CRC cell lines with KRAS mutations (DLD‐1, HCT116, and LoVo) were used to test the effect of cetuximab, BKM120, and cetuximab plus BKM120 on cell proliferation in vitro and in vivo. BKM120 reduced cell proliferation in a concentration‐dependent manner in the LoVo (PI3KCA wild type) as well as the HCT116 and DLD1 cells (that carry a PI3KCA mutation). BKM120 only inhibited ERK phosphorylation in LoVo cells (PIK3CA wild type), but not in DLD1 or HCT116 cells at a concentration of 1 μmol/L. Treatment with cetuximab and BKM120 significantly reduced the growth of xenograft tumors originating from KRAS mutant cells compared with cetuximab alone (P = 0.034). BKM120 may overcome cetuximab resistance in colon cancer cells with KRAS mutation.