Expression of anti-apoptotic factors modulates Apo2L/TRAIL resistance in colon carcinoma cells

Deciphering treatment resistance in metastatic colorectal cancer: roles of drug transports, EGFR mutations, and HGF/c-MET signaling

In 2023, colorectal cancer (CRC) is the third most diagnosed malignancy and the third leading cause of cancer death worldwide. At the time of the initial visit, 20% of patients diagnosed with CRC have metastatic CRC (mCRC), and another 25% who present with localized disease will later develop metastases. Despite the improvement in response rates with various modulation strategies such as chemotherapy combined with targeted therapy, radiotherapy, and immunotherapy, the prognosis of mCRC is poor, with a 5-year survival rate of 14%, and the primary reason for treatment failure is believed to be the development of resistance to therapies. Herein, we provide an overview of the main mechanisms of resistance in mCRC and specifically highlight the role of drug transports, EGFR, and HGF/c-MET signaling pathway in mediating mCRC resistance, as well as discuss recent therapeutic approaches to reverse resistance caused by drug transports and resistance to anti-EGFR blockade caused by mutations in EGFR and alteration in HGF/c-MET signaling pathway.

Escaping cell death via TRAIL decoy receptors: a systematic review of their roles and expressions in colorectal cancer

The development of targeted therapy such as tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL)-based therapy has gained increasing attention as a promising new approach in cancer therapy. TRAIL specifically targets cancer cells while sparing the normal cells, thus, limiting the known side effects of the majority anti-cancer therapies. As more extensive research and clinical trials are conducted, resistance to TRAIL molecule has become one of the significant issues associated with the failure of TRAIL in treating colorectal cancer (CRC). To date, the exact mechanism by which TRAIL resistance may have occurred remains unknown. Interestingly, recent studies have revealed the critical role of the TRAIL decoy receptor family; consisting of decoy receptor 1 (DcR1; also known as TRAIL-R3), decoy receptor 2 (DcR2; also known as TRAIL-R4), and osteoprotegerin (OPG) in driving TRAIL resistance. This review highlights the expression of the decoy receptors in CRC and its possible association with the reduction in sensitivity towards TRAIL treatment based on the currently available in vitro, in vivo, and human studies. Additionally, discrepancies between the outcomes from different research groups are discussed, and essential areas are highlighted for future investigation of the roles of decoy receptors in modulating TRAIL-induced apoptosis. Overcoming TRAIL resistance through modulating the expression(s) and elucidating the role(s) of TRAIL decoy receptors hold great promise for TRAIL-based therapies to be extensively explored in treating human cancers including CRC.

Drug Resistance in Colorectal Cancer: From Mechanism to Clinic

Colorectal cancer (CRC) is one of the leading causes of death worldwide. The 5-year survival rate is 90% for patients with early CRC, 70% for patients with locally advanced CRC, and 15% for patients with metastatic CRC (mCRC). In fact, most CRC patients are at an advanced stage at the time of diagnosis. Although chemotherapy, molecularly targeted therapy and immunotherapy have significantly improved patient survival, some patients are initially insensitive to these drugs or initially sensitive but quickly become insensitive, and the emergence of such primary and secondary drug resistance is a significant clinical challenge. The most direct cause of resistance is the aberrant anti-tumor drug metabolism, transportation or target. With more in-depth research, it is found that cell death pathways, carcinogenic signals, compensation feedback loop signal pathways and tumor immune microenvironment also play essential roles in the drug resistance mechanism. Here, we assess the current major mechanisms of CRC resistance and describe potential therapeutic interventions.

Harnessing TRAIL-Induced Apoptosis Pathway for Cancer Immunotherapy and Associated Challenges

The immune cytokine tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has attracted rapidly evolving attention as a cancer treatment modality because of its competence to selectively eliminate tumor cells without instigating toxicity in vivo. TRAIL has revealed encouraging promise in preclinical reports in animal models as a cancer treatment option; however, the foremost constraint of the TRAIL therapy is the advancement of TRAIL resistance through a myriad of mechanisms in tumor cells. Investigations have documented that improvement of the expression of anti-apoptotic proteins and survival or proliferation involved signaling pathways concurrently suppressing the expression of pro-apoptotic proteins along with down-regulation of expression of TRAILR1 and TRAILR2, also known as death receptor 4 and 5 (DR4/5) are reliable for tumor cells resistance to TRAIL. Therefore, it seems that the development of a therapeutic approach for overcoming TRAIL resistance is of paramount importance. Studies currently have shown that combined treatment with anti-tumor agents, ranging from synthetic agents to natural products, and TRAIL could result in induction of apoptosis in TRAIL-resistant cells. Also, human mesenchymal stem/stromal cells (MSCs) engineered to generate and deliver TRAIL can provide both targeted and continued delivery of this apoptosis-inducing cytokine. Similarly, nanoparticle (NPs)-based TRAIL delivery offers novel platforms to defeat barricades to TRAIL therapeutic delivery. In the current review, we will focus on underlying mechanisms contributed to inducing resistance to TRAIL in tumor cells, and also discuss recent findings concerning the therapeutic efficacy of combined treatment of TRAIL with other antitumor compounds, and also TRAIL-delivery using human MSCs and NPs to overcome tumor cells resistance to TRAIL.

Selective Tumor Cell Apoptosis and Tumor Regression in CDH17-Positive Colorectal Cancer Models using BI 905711, a Novel Liver-Sparing TRAILR2 Agonist

Activation of TRAILR2 has emerged as an important therapeutic concept in cancer treatment. TRAILR2 agonistic molecules have only had limited clinical success, to date, due either to lack of efficacy or hepatotoxicity. BI 905711 is a novel tetravalent bispecific antibody targeting both TRAILR2 and CDH17 and represents a novel liver-sparing TRAILR2 agonist specifically designed to overcome the disadvantages of previous strategies. Here, we show that BI 905711 effectively triggered apoptosis in a broad panel of CDH17-positive colorectal cancer tumor cells in vitro. Efficient induction of apoptosis was dependent on the presence of CDH17, as exemplified by the greater than 1,000-fold drop in potency in CDH17-negative cells. BI 905711 demonstrated single-agent tumor regressions in CDH17-positive colorectal cancer xenografts, an effect that was further enhanced upon combination with irinotecan. Antitumor efficacy correlated with induction of caspase activation, as measured in both the tumor and plasma. Effective tumor growth inhibition was further demonstrated across a series of different colorectal cancer PDX models. BI 905711 induced apoptosis in both a cis (same cell) as well as trans (adjacent cell) fashion, translating into significant antitumor activity even in xenograft models with heterogeneous CDH17 expression. In summary, we demonstrate that BI 905711 has potent and selective antitumor activity in CDH17-positive colorectal cancer models both in vitro and in vivo. The high prevalence of over 95% CDH17-positive tumors in patients with colorectal cancer, the molecule preclinical efficacy together with its potential for a favorable safety profile, support the ongoing BI 905711 phase I trial in colorectal cancer and additional CDH17-positive cancer types (NCT04137289).

Genome-scale analysis identifies paralog lethality as a vulnerability of chromosome 1p loss in cancer

Functional redundancy shared by paralog genes may afford protection against genetic perturbations, but it can also result in genetic vulnerabilities due to mutual interdependency1-5. Here, we surveyed genome-scale short hairpin RNA and CRISPR screening data on hundreds of cancer cell lines and identified MAGOH and MAGOHB, core members of the splicing-dependent exon junction complex, as top-ranked paralog dependencies6-8. MAGOHB is the top gene dependency in cells with hemizygous MAGOH deletion, a pervasive genetic event that frequently occurs due to chromosome 1p loss. Inhibition of MAGOHB in a MAGOH-deleted context compromises viability by globally perturbing alternative splicing and RNA surveillance. Dependency on IPO13, an importin-β receptor that mediates nuclear import of the MAGOH/B-Y14 heterodimer9, is highly correlated with dependency on both MAGOH and MAGOHB. Both MAGOHB and IPO13 represent dependencies in murine xenografts with hemizygous MAGOH deletion. Our results identify MAGOH and MAGOHB as reciprocal paralog dependencies across cancer types and suggest a rationale for targeting the MAGOHB-IPO13 axis in cancers with chromosome 1p deletion.

Sortase A-aided Escherichia coli expression system for functional osteoprotegerin cysteine-rich domain

As a natural inhibitor of the receptor activator of nuclear factor-кB ligand (RANKL), osteprotegerin (OPG) is considered a promising treatment for metabolic bone diseases. Typical approaches for preparing recombinant OPG or its derivatives employ eukaryotic expression systems. Due to the advantages of a prokaryotic expression system, which include its convenience, low cost, and abundant production, in this study, we establish a strategy for preparing functional OPG using the Escherichia coli expression system. After initial failures in preparation of OPG and its truncation, OPG cysteine-rich domain (OPG-CRD/OPGT) by using pET and pGEX vectors, we constructed a sortase A (SrtA)-aided E. coli expression system, in which the expressed protein was a self-cleaving SrtA fusion protein. Using this system, we successfully prepared the recombinant OPGT protein. The BIAcore analyses indicated that the prepared OPGT had high affinities in binding with RANKL and TRAIL. Cell experiments confirmed the inhibitory effects of the prepared OPGT on RANKL-induced osteoclast differentiation and TRAIL-induced tumor cell apoptosis. The sortase A-aided E. coli expression system for OPGT established in this study may contribute to further studies and commercial applications of OPG.

The probiotic Propionibacterium freudenreichii as a new adjuvant for TRAIL-based therapy in colorectal cancer

TNF-Related Apoptosis-Inducing Ligand (TRAIL) is a well-known apoptosis inducer, which activates the extrinsic death pathway. TRAIL is pro-apoptotic on colon cancer cells, while not cytotoxic towards normal healthy cells. However, its clinical use is limited by cell resistance to cell death which occurs in approximately 50% of cancer cells. Short Chain Fatty Acids (SCFA) are also known to specifically induce apoptosis of cancer cells. In accordance, we have shown that food grade dairy propionibacteria induce intrinsic apoptosis of colon cancer cells, via the production and release of SCFA (propionate and acetate) acting on mitochondria. Here, we investigated possible synergistic effect between Propionibacterium freudenreichii and TRAIL. Indeed, we hypothesized that acting on both extrinsic and intrinsic death pathways may exert a synergistic pro-apoptotic effect. Whole transcriptomic analysis demonstrated that propionibacterial supernatant or propionibacterial metabolites (propionate and acetate), in combination with TRAIL, increased pro-apoptotic gene expression (TRAIL-R2/DR5) and decreased anti-apoptotic gene expression (FLIP, XIAP) in HT29 human colon cancer cells. The revealed synergistic pro-apoptotic effect, depending on both death receptors (TRAIL-R1/DR4, TRAIL-R2/DR5) and caspases (caspase-8, -9 and -3) activation, was lethal on cancer cells but not on normal human intestinal epithelial cells (HIEC), and was inhibited by Bcl-2 expression. Finally, milk fermented by P. freudenreichii induced HT29 cells apoptosis and enhanced TRAIL cytotoxic activity, as did P. freudenreichii DMEM culture supernatants or its SCFA metabolites. These results open new perspectives for food grade P. freudenreichii-containing products in order to potentiate TRAIL-based cancer therapy in colorectal cancer.

Apo2L/TRAIL and the death receptor 5 agonist antibody AMG 655 cooperate to promote receptor clustering and antitumor activity

Death receptor agonist therapies have exhibited limited clinical benefit to date. Investigations into why Apo2L/TRAIL and AMG 655 preclinical data were not predictive of clinical response revealed that coadministration of Apo2L/TRAIL with AMG 655 leads to increased antitumor activity in vitro and in vivo. The combination of Apo2L/TRAIL and AMG 655 results in enhanced signaling and can sensitize Apo2L/TRAIL-resistant cells. Structure determination of the Apo2L/TRAIL-DR5-AMG 655 ternary complex illustrates how higher order clustering of DR5 is achieved when both agents are combined. Enhanced agonism generated by combining Apo2L/TRAIL and AMG 655 provides insight into the limited efficacy observed in previous clinical trials and suggests testable hypotheses to reconsider death receptor agonism as a therapeutic strategy.

Osteoblasts display different responsiveness to TRAIL-induced apoptosis during their differentiation process

Apoptosis can occur throughout the life span of osteoblasts (OBs), beginning from the early stages of differentiation and continuing throughout all stages of their working life. Here, we investigated the effects of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) on normal human OBs showing for the first time that the expression of TRAIL receptors is modulated during OB differentiation. In particular, the TRAIL receptor ratio was in favor of the deaths because of the low expression of DcR2 in undifferentiated OBs, differently it was shifted toward the decoys in differentiated ones. Undifferentiated OBs treated with TRAIL showed reduced cell viability, whereas differentiated OBs displayed TRAIL resistance. The OB sensitiveness to TRAIL was due to the up-regulation of DR5 and the down-regulation of DcR2. The main death receptor involved in TRAIL-reduced OB viability was DR5 as demonstrated by the rescue of cell viability observed in the presence of anti-DR5 neutralizing antibody. Besides the ratio of TRAIL receptors, the sensitivity of undifferentiated OBs to TRAIL-cytotoxic effect was also associated with low mRNA levels of intracellular anti-apoptotic proteins, such as cFLIP, the activation of caspase-8 and -3, as well as the DNA fragmentation. This study suggests that apoptotic effect exerted by TRAIL/TRAIL-receptor system on normal human OB is strictly dependent upon cell differentiation status.

DHA-mediated enhancement of TRAIL-induced apoptosis in colon cancer cells is associated with engagement of mitochondria and specific alterations in sphingolipid metabolism

Docosahexaenoic acid (DHA), an n-3 polyunsaturated fatty acid present in fish oil, may exert cytotoxic and/or cytostatic effects on colon cancer cells when applied individually or in combination with some anticancer drugs. Here we demonstrate a selective ability of subtoxic doses of DHA to enhance antiproliferative and apoptotic effects of clinically useful cytokine TRAIL (tumor necrosis factor-related apoptosis inducing ligand) in cancer but not normal human colon cells. DHA-mediated stimulation of TRAIL-induced apoptosis was associated with extensive engagement of mitochondrial pathway (Bax/Bak activation, drop of mitochondrial membrane potential, cytochrome c release), activation of endoplasmic reticulum stress response (CHOP upregulation, changes in PERK level), decrease of cellular inhibitor of apoptosis protein (XIAP, cIAP1) levels and significant changes in sphingolipid metabolism (intracellular levels of ceramides, hexosyl ceramides, sphingomyelines, sphingosines; HPLC/MS/MS). Interestingly, we found significant differences in representation of various classes of ceramides (especially C16:0, C24:1) between the cancer and normal colon cells treated with DHA and TRAIL, and suggested their potential role in the regulation of the cell response to the drug combination. These study outcomes highlight the potential of DHA for a new combination therapy with TRAIL for selective elimination of colon cancer cells via simultaneous targeting of multiple steps in apoptotic pathways.

Mouse monoclonal antibodies to transient receptor potential ankyrin 1 act as antagonists of multiple modes of channel activation

The transient receptor potential ankyrin 1 (TRPA1) channel has been implicated in different pathophysiologies that include asthma, cough, itch, and inflammatory pain. Agonists of TRPA1 such as mustard oil and its key component allyl isothiocyanate (AITC) cause pain and neurogenic inflammation in humans and pain behaviors in rodents. Hence, TRPA1 antagonists are being pursued as potential therapeutics. With the goal of generating monoclonal antibodies (mAbs) to human TRPA1 that could act as selective antagonists, we immunized mice with a variety of antigens expressing TRPA1 channels. After generation of hybridomas, the hybridoma conditioned media were screened to identify the mAbs that bind TRPA1 channels by a flow cytometry assay utilizing U2OS or Chinese hamster ovary (CHO) cells stably expressing TRPA1. The purified IgGs from the hybridomas that showed selective binding to TRPA1 were evaluated for antagonism in agonist-induced (45)Ca(2+) uptake assays using CHO-TRPA1 cells. Several of the mAbs showed concentration-dependent inhibition of AITC and cold (4°C) activation of TRPA1. The most potent mAb, 2B10, had IC50 values of approximately 260 and 90 nM in the two assays, respectively. These antagonist mAbs also blocked osmotically activated TRPA1 as well as activation by an endogenous agonist (4-oxo-2-nonenal). In summary, we generated mouse mAbs against TRPA1 that act as antagonists of multiple modes of TRPA1 activation.

Death receptor 5 agonistic antibody PRO95780: preclinical pharmacokinetics and concentration-effect relationship support clinical dose and regimen selection

PURPOSE

PRO95780, a human monoclonal antibody (mAb) against death receptor 5 (DR5/TRAIL-R2/TNFRSF10B), was developed for the treatment for cancer. Our objective was to characterize pharmacokinetics (PK) in mice, rats, and cynomolgus monkeys and concentration-effect relationships of PRO95780 in xenograft mouse models of human cancers; this would guide the selection of dose and regimen for clinical trials.

METHODS

The PK profiles were determined in mice, rats, and cynomolgus monkeys. Three xenograft models with a wide range of in vitro sensitivities to PRO95780 were selected for efficacy studies. Tumoristatic serum concentrations (TSCs) were determined using PK/pharmacodynamic (PD) modeling with tumor growth as a PD endpoint. A species-invariant time PK scaling method was employed to estimate disposition in humans using PK data in cynomolgus monkeys. Furthermore, the predicted human PK parameters were used to estimate dose and regimen to achieve TSC observed in mice at the steady-state trough concentrations (C trough ss) in the clinic.

RESULTS

Linear PK was observed across species. A serum concentration of 22 μg/mL was identified to be the target TSC in mice. A dose of 10 mg/kg administered once every 2 weeks (Q2W) was predicted to achieve a TSC at C trough ss in 95 % of patients.

CONCLUSIONS

PRO95780 has linear PK in mice, rats, and monkeys. Estimated TSCs varied among different xenograft models. A projected target dose in humans is achievable for Q2W administration within the dose range used for other commercial mAbs.

The flavonolignan silibinin potentiates TRAIL-induced apoptosis in human colon adenocarcinoma and in derived TRAIL-resistant metastatic cells

Silibinin, a flavonolignan, is the major active component of the milk thistle plant (Silybum marianum) and has been shown to possess anti-neoplastic properties. TNF-related apoptosis-inducing ligand (TRAIL) is a promising anti-cancer agent which selectively induces apoptosis in cancer cells. However, resistance to TRAIL-induced apoptosis is an important and frequent problem in cancer treatment. In this study, we investigated the effect of silibinin and TRAIL in an in vitro model of human colon cancer progression, consisting of primary colon tumor cells (SW480) and their derived TRAIL-resistant metastatic cells (SW620). We showed by flow cytometry that silibinin and TRAIL synergistically induced cell death in the two cell lines. Up-regulation of death receptor 4 (DR4) and DR5 by silibinin was shown by RT-PCR and by flow cytometry. Human recombinant DR5/Fc chimera protein that has a dominant-negative effect by competing with the endogenous receptors abrogated cell death induced by silibinin and TRAIL, demonstrating the activation of the death receptor pathway. Synergistic activation of caspase-3, -8, and -9 by silibinin and TRAIL was shown by colorimetric assays. When caspase inhibitors were used, cell death was blocked. Furthermore, silibinin and TRAIL potentiated activation of the mitochondrial apoptotic pathway and down-regulated the anti-apoptotic proteins Mcl-1 and XIAP. The involvement of XIAP in sensitization of the two cell lines to TRAIL was demonstrated using the XIAP inhibitor embelin. These findings demonstrate the synergistic action of silibinin and TRAIL, suggesting chemopreventive and therapeutic potential which should be further explored.

Macrophage migration inhibitory factor produced by the tumour stroma but not by tumour cells regulates angiogenesis in the B16-F10 melanoma model

Background:

Macrophage migration inhibitory factor (MIF) has been proposed as a link between inflammation and tumorigenesis. Despite its potentially broad influence in tumour biology and prevalent expression, the value of MIF as a therapeutic target in cancer remains unclear. We sought to validate MIF in tumour models by achieving a complete inhibition of its expression in tumour cells and in the tumour stroma.

Methods:

We used MIF shRNA-transduced B16-F10 melanoma cells implanted in wild-type and MIF−/− C57Bl6 mice to investigate the effect of loss of MIF on tumour growth. Cytokine detection and immunohistochemistry (IHC) were used to evaluate tumours ex vivo.

Results:

Macrophage migration inhibitory factor shRNA inhibited expression of MIF protein by B16-F10 melanoma cells in vitro and in vivo. In vitro, the loss of MIF in this cell line resulted in a decreased response to hypoxia as indicated by reduced expression of VEGF. In vivo the growth of B16-F10 tumours was inhibited by an average of 47% in the MIF−/− mice compared with wild-type but was unaffected by loss of MIF expression by the tumour cells. Immunohistochemistry analysis revealed that microvessel density was decreased in tumours implanted in the MIF−/− mice. Profiling of serum cytokines showed a decrease in pro-angiogenic cytokines in MIF−/− mice.

Conclusion:

We report that the absence of MIF in the host resulted in slower tumour growth, which was associated with reduced vascularity. While the major contribution of MIF appeared to be in the regulation of angiogenesis, tumour cell-derived MIF played a negligible role in this process.

Evaluation of pharmacodynamic biomarkers in a Phase 1a trial of dulanermin (rhApo2L/TRAIL) in patients with advanced tumours

Background:

Dulanermin (rhApo2L/TRAIL) induces apoptosis by binding to death receptors DR4 and DR5, leading to caspase activation and subsequent cell death. A Phase1a trial evaluated the safety and tolerability of dulanermin in patients with advanced tumours. One aim was to develop and validate pharmacodynamic biomarkers to monitor dulanermin activity in patient serum.

Methods:

We optimised assays to measure the cell-death markers caspase 3/7, cytokeratin 18 and genomic DNA in serum. Mice bearing Colo205 xenografts were treated with dulanermin and sera were collected and assayed for apoptotic markers. Upon validating these assays, we monitored apoptotic markers in patients who received dulanermin.

Results:

We detected transient increases in apoptotic markers in mouse sera 8–24 h after dulanermin treatment. This increase was dose-dependent and correlated with active caspase 3 detected by IHC in Colo205 tumours. A statistically significant increase in serum caspase 3/7 was detected in cohorts of colorectal and sarcoma patients 24 h after receiving dulanermin dosed above 4 mg kg⁻¹.

Conclusion:

Owing to limited responses in the Phase 1a study, the changes in circulating cell-death markers were not evaluable. Future studies with dulanermin are needed to determine the utility of these assays with respect to providing evidence of activity or predicting overall response.

Naturally occurring, tumor-specific, therapeutic proteins

The emerging approach to cancer treatment known as targeted therapies offers hope in improving the treatment of therapy-resistant cancers. Recent understanding of the molecular pathogenesis of cancer has led to the development of targeted novel drugs such as monoclonal antibodies, small molecule inhibitors, mimetics, antisense and small interference RNA-based strategies, among others. These compounds act on specific targets that are believed to contribute to the development and progression of cancers and resistance of tumors to conventional therapies. Delivered individually or combined with chemo- and/or radiotherapy, such novel drugs have produced significant responses in certain types of cancer. Among the most successful novel compounds are those which target tyrosine kinases (imatinib, trastuzumab, sinutinib, cetuximab). However, these compounds can cause severe side-effects as they inhibit pathways such as epidermal growth factor receptor (EGFR) or platelet-derived growth factor receptor, which are also important for normal functions in non-transformed cells. Recently, a number of proteins have been identified which show a remarkable tumor-specific cytotoxic activity. This toxicity is independent of tumor type or specific genetic changes such as p53, pRB or EGFR aberrations. These tumor-specific killer proteins are either derived from common human and animal viruses such as E1A, E4ORF4 and VP3 (apoptin) or of cellular origin, such as TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) and MDA-7 (melanoma differentiation associated-7). This review aims to present a current overview of a selection of these proteins with preferential toxicity among cancer cells and will provide an insight into the possible mechanism of action, tumor specificity and their potential as novel tumor-specific cancer therapeutics.

TNFα cooperates with IFN-γ to repress Bcl-xL expression to sensitize metastatic colon carcinoma cells to TRAIL-mediated apoptosis

Background

TNF-related apoptosis-inducing ligand (TRAIL) is an immune effector molecule that functions as a selective anti-tumor agent. However, tumor cells, especially metastatic tumor cells often exhibit a TRAIL-resistant phenotype, which is currently a major impediment in TRAIL therapy. The aim of this study is to investigate the synergistic effect of TNFα and IFN-γ in sensitizing metastatic colon carcinoma cells to TRAIL-mediated apoptosis.

Methodology/Principal Findings

The efficacy and underlying molecular mechanism of cooperation between TNFα and IFN-γ in sensitizing metastatic colon carcinoma cells to TRAIL-mediated apoptosis were examined. The functional significance of TNFα- and IFN-γ-producing T lymphocyte immunotherapy in combination with TRAIL therapy in suppression of colon carcinoma metastasis was determined in an experimental metastasis mouse model. We observed that TNFα or IFN-γ alone exhibits minimal sensitization effects, but effectively sensitized metastatic colon carcinoma cells to TRAIL-induced apoptosis when used in combination. TNFα and IFN-γ cooperate to repress Bcl-xL expression, whereas TNFα represses Survivin expression in the metastatic colon carcinoma cells. Silencing Bcl-xL expression significantly increased the metastatic colon carcinoma cell sensitivity to TRAIL-induced apoptosis. Conversely, overexpression of Bcl-xL significantly decreased the tumor cell sensitivity to TRAIL-induced apoptosis. Furthermore, TNFα and IFN-γ also synergistically enhanced TRAIL-induced caspase-8 activation. TNFα and IFN-γ was up-regulated in activated primary and tumor-specific T cells. TRAIL was expressed in tumor-infiltrating immune cells in vivo, and in tumor-specific cytotoxic T lymphocytes (CTL) ex vivo. Consequently, TRAIL therapy in combination with TNFα/IFN-γ-producing CTL adoptive transfer immunotherapy effectively suppressed colon carcinoma metastasis in vivo.

Conclusions/Significance

TNFα and IFN-γ cooperate to overcome TRAIL resistance at least partially through enhancing caspase 8 activation and repressing Bcl-xL expression. Combined CTL immunotherapy and TRAIL therapy hold great promise for further development for the treatment of metastatic colorectal cancer.

Prognostic significance of TRAIL signaling molecules in stage II and III colorectal cancer

PURPOSE

We previously found that cellular FLICE-inhibitory protein (c-FLIP), caspase 8, and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor 2 (DR5) are major regulators of cell viability and chemotherapy-induced apoptosis in colorectal cancer. In this study, we determined the prognostic significance of c-FLIP, caspase 8, TRAIL and DR5 expression in tissues from patients with stage II and III colorectal cancer.

EXPERIMENTAL DESIGN

Tissue microarrays were constructed from matched normal and tumor tissue derived from patients (n = 253) enrolled in a phase III trial of adjuvant 5-fluorouracil-based chemotherapy versus postoperative observation alone. TRAIL, DR5, caspase 8, and c-FLIP expression levels were determined by immunohistochemistry.

RESULTS

Colorectal tumors displayed significantly higher expression levels of c-FLIP (P < 0.001), caspase 8 (P = 0.01), and DR5 (P < 0.001), but lower levels of TRAIL (P < 0.001) compared with matched normal tissue. In univariate analysis, higher TRAIL expression in the tumor was associated with worse overall survival (P = 0.026), with a trend to decreased relapse-free survival (RFS; P = 0.06), and higher tumor c-FLIP expression was associated with a significantly decreased RFS (P = 0.015). Using multivariate predictive modeling for RFS in all patients and including all biomarkers, age, treatment, and stage, we found that the model was significant when the mean tumor c-FLIP expression score and disease stage were included (P < 0.001). As regards overall survival, the overall model was predictive when both TRAIL expression and disease stage were included (P < 0.001).

CONCLUSIONS

High c-FLIP and TRAIL expression may be independent adverse prognostic markers in stage II and III colorectal cancer and might identify patients most at risk of relapse.

Scatter factor protects tumor cells against apoptosis caused by TRAIL

Scatter factor (SF) and its receptor c-Met are overexpressed in various tumor types, and their expression often correlates with a poor prognosis. The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), is a proposed tumor-specific chemotherapy agent, but its clinical usage is limited by acquisition of TRAIL resistance by tumors. The goals of this study were to determine whether and how SF protects tumor cells against TRAIL and whether SF-induced TRAIL resistance could be reversed. We used MTT assays, trypan blue dye exclusion assays, apoptosis assays, RNA interference, luciferase reporter assays, immunoprecipitation/western blotting, and other cell biological techniques to study SF protection of cultured human tumor cells against TRAIL. SF conferred resistance to TRAIL in various human prostate carcinoma and breast carcinoma cell lines. SF inhibited TRAIL-induced caspase-3 activation, poly (ADP-ribose) polymerase cleavage, and cell death. SF protection against TRAIL required c-Akt; but unlike protection against adriamycin, it did not require Src signaling or the classical pathway of nuclear factor-kappaB activation. Protection against TRAIL was blocked by knockdown of X-linked inhibitor of apoptosis or FLICE-inhibitor protein (FLIP) (a component of the death-inducing signaling complex). We found that c-Met physically associates with several TRAIL receptors and SF regulates their protein stability. Protection against TRAIL was blocked by a novel small molecule inhibitor of c-Met (PHA665752) and by an inhibitor of cyclooxygenase 2. In conclusion, these findings elucidate potential mechanisms of TRAIL resistance in tumors that overexpress the SF/c-Met and identify possible means of reversing this resistance.

TRAILing death in cancer

The observation that certain types of cancer express death receptors on their cell surface has triggered heightened interest in exploring the potential of receptor ligation as a novel anti-cancer modality, and since the expression is somewhat restricted to cancer cells the therapeutic implications are very promising. One such death receptor ligand belonging to the tumor necrosis receptor (TNF) superfamily, TNF-related apoptosis-inducing ligand (TRAIL), has been in the limelight as a tumor selective molecule that transmits death signal via ligation to its receptors (TRAIL-R1 and TRAIL-R2 or death receptors 4 and 5; DR4 and DR5). Interestingly, TRAIL-induced apoptosis exhibits hallmarks of extrinsic as well as intrinsic death pathways, and, therefore, is subject to regulation both at the cell surface receptor level as well as more downstream at the post-mitochondrial level. Despite the remarkable selectivity of DR expression on cancer cell surface, development of resistance to TRAIL-induced apoptosis remains a major challenge. Therefore, unraveling the cellular and molecular mechanisms of TRAIL resistance as well as identifying strategies to overcome this problem for an effective therapeutic response remains the cornerstone of many research endeavors. This review aims at presenting an overview of the biology, function and translational relevance of TRAIL with a specific view to discussing the various regulatory mechanisms and the current trends in reverting TRAIL resistance of cancer cells with the obvious implication of an improved clinical outcome.

Sodium butyrate sensitizes human colon adenocarcinoma COLO 205 cells to both intrinsic and TNF-alpha-dependent extrinsic apoptosis

Overexpression of cFLIP protein seems to be critical in the antiapoptotic mechanism of immune escape of human COLO 205 colon adenocarcinoma cells. Actually, cFLIP appears to inhibit the death receptor ligand-mediated cell death. Application of the metabolic inhibitor sodium butyrate (NaBt), short-chain volatile fatty acid, sensitized COLO 205 cells to TNF-alpha-mediated apoptosis. Western-blot analysis revealed that the susceptibility of human COLO 205 cells to apoptogenic stimuli resulted from time-dependent reduction in cFLIP and simultaneous up-regulation of TNF-R1 protein levels. Additionally, the combined TNF-alpha and NaBt treatment caused cleavage of Bid and caspase-9 activation, as well as cytochrome c release from mitochondria. Thus, the evidence of this study indicates that NaBt facilitates the death receptor signal evoked by TNF-alpha. Moreover, NaBt alone initiated intrinsic apoptosis, that in turn was abolished by intracellular BCL-2 delivery. It confirms the involvement of mitochondria in the proapoptotic activity of NaBt. The activation of mitochondrial pathway was substantiated by up-regulated expression of BAK with concomitant reduction of antiapoptotic BCL-x(L), XIAP and survivin proteins. These findings suggest that NaBt could represent a good candidate for the new therapeutic strategy aimed to improve chemo- and immunotherapy of colon cancer.

Bisindolylmaleimide IX facilitates extrinsic and initiates intrinsic apoptosis in TNF-alpha-resistant human colon adenocarcinoma COLO 205 cells

Human COLO 205 colon adenocarcinoma cells are immune to extrinsic apoptosis induced by immunomodulatory cytokines. Among the antiapoptotic mechanisms responsible for the immune escape, the overexpression of the cFLIP protein seems to be critical. cFLIP appears to inhibit the TNF-alpha-induced death receptor signal. The application of the metabolic inhibitor bisindolylmaleimide IX (Bis-IX), known as a potent PKC repressor, sensitized COLO 205 cells to TNF-alpha-mediated apoptosis. The Western-blot analysis revealed that the susceptibility of human COLO 205 cells to apoptogenic stimuli resulted from time-dependent reduction in cFLIP(L) and TRADD protein levels. At the same time, the level of FADD protein was up-regulated. Additionally, the combined TNF-alpha and Bis-IX treatment caused cleavages of Bid and procaspase-9, as well as cytochrome c release. Thus, the evidence of this study indicates that Bis-IX facilitates the death receptor signal mediated by TNF-R1. Moreover, Bis-IX alone initiated intrinsic apoptosis, which could be abolished by Bcl-2 delivery. It heralds the involvement of mitochondria in caspase-8-independent intrinsic apoptosis. In turn, the treatment with bisindolylmaleimide III (Bis-III) did not assist TNF-alpha-dependent apoptosis.

Akt and XIAP regulate the sensitivity of human uterine cancer cells to cisplatin, doxorubicin and taxol

We have investigated the interrelationship between two anti-apoptotic factors, XIAP and Akt, and their role in chemoresistance of uterine cancer cells. We used one cervical cancer cell line (HeLa) and two endometrial cancer cell lines (KLE and Ishikawa) as a model. The three drugs decreased Akt and XIAP content and induced apoptosis in P-Akt-negative HeLa cells. In P-Akt1/3-positive Ishikawa cells apoptosis induction correlated with XIAP decrease. P-Akt1/2/3-positive KLE cells showed maximum chemoresistance as XIAP and Akt levels/phosphorylation remained stable in response to the three drugs, and only cisplatin could significantly induce apoptosis. We found that XIAP and Akt were functionally linked in uterine cancer cells, as downregulation of XIAP with RNAi decreased P-Akt levels, and inhibition of PI3-K/Akt activity using LY294002 decreased XIAP content. Overexpression of constitutively active Akt isoforms in HeLa cells induced isoform-specific sensitivity to doxorubicin and taxol but not cisplatin. XIAP RNAi increased the cell-specific sensitivity to cisplatin and doxorubicin but not taxol. Finally, we found P-Akt immunoreactivity in epithelial cells from multiple human endometrial carcinoma tumors, suggesting that Akt may also regulate chemosensitivity in uterine cancers in vivo. Altogether these results highlight an intertwined role for specific Akt isoforms and XIAP in chemoresistance of uterine cancer cells.

Apoptosis resistance in epithelial tumors is mediated by tumor-cell-derived interleukin-4

We investigated the mechanisms involved in the resistance to cell death observed in epithelial cancers. Here, we identify that primary epithelial cancer cells from colon, breast and lung carcinomas express high levels of the antiapoptotic proteins PED, cFLIP, Bcl-xL and Bcl-2. These cancer cells produced interleukin-4 (IL-4), which amplified the expression levels of these antiapoptotic proteins and prevented cell death induced upon exposure to TRAIL or other drug agents. IL-4 blockade resulted in a significant decrease in the growth rate of epithelial cancer cells and sensitized them, both in vitro and in vivo, to apoptosis induction by TRAIL and chemotherapy via downregulation of the antiapoptotic factors PED, cFLIP, Bcl-xL and Bcl-2. Furthermore, we provide evidence that exogenous IL-4 was able to upregulate the expression levels of these antiapoptotic proteins and potently stabilized the growth of normal epithelial cells rendering them apoptosis resistant. In conclusion, IL-4 acts as an autocrine survival factor in epithelial cells. Our results indicate that inhibition of IL-4/IL-4R signaling may serve as a novel treatment for epithelial cancers.

The Potential of Death Receptor 4– and 5–Directed Therapies in the Treatment of Lung Cancer

Aberrations of the intracellular apoptotic balance--reducing proapoptotic signaling and increasing antiapoptotic signaling--are common in cancer cells. Increasing apoptosis through the direct manipulation of the apoptotic machinery offers novel anticancer strategies. Of the 2 main interacting proapoptotic pathways, the extrinsic pathway is characterized by ligand dependent stimulation of cell surface death receptor (DRs). Recombinant ligand and agonistic monoclonal antibodies directed against the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors, DR 4 (TRAIL-R1) and/or DR 5 (TRAIL-R2), are now being explored within clinical trials. These agents appear well tolerated with hints of single-agent activity in lymphoma, colorectal cancer, chondrosarcoma, and non-small-cell lung cancer. Numerous molecular factors influencing sensitivity or resistance have been identified in vitro, but the determinants of clinical benefit remain unclear. Preclinically, synergy with cytotoxic chemotherapy and radiation therapy is well documented, with DR4/5 stimulation helping to tip the intracellular processing of multiple stimuli in favor of cell death. Provided that a wide therapeutic margin relative to normal cells can be maintained, maximizing apoptotic responses to standard treatments through DR4/5-directed therapy, with or without additional blockade of antiapoptotic signaling, has considerable potential in the treatment of lung cancer. Trials of DR4/5-directed therapies in combination with standard first-line chemotherapy for non-small-cell lung cancer are under way.