Synergistic tumoricidal effect between celecoxib and adenoviral-mediated delivery of mda-7 in human breast cancer cells

Insights into the Mechanisms of Action of MDA-7/IL-24: A Ubiquitous Cancer-Suppressing Protein

Melanoma differentiation associated gene-7/interleukin-24 (MDA-7/IL-24), a secreted protein of the IL-10 family, was first identified more than two decades ago as a novel gene differentially expressed in terminally differentiating human metastatic melanoma cells. MDA-7/IL-24 functions as a potent tumor suppressor exerting a diverse array of functions including the inhibition of tumor growth, invasion, angiogenesis, and metastasis, and induction of potent "bystander" antitumor activity and synergy with conventional cancer therapeutics. MDA-7/IL-24 induces cancer-specific cell death through apoptosis or toxic autophagy, which was initially established in vitro and in preclinical animal models in vivo and later in a Phase I clinical trial in patients with advanced cancers. This review summarizes the history and our current understanding of the molecular/biological mechanisms of MDA-7/IL-24 action rendering it a potent cancer suppressor.

Role of MDA-7/IL-24 a Multifunction Protein in Human Diseases

Subtraction hybridization identified genes displaying differential expression as metastatic human melanoma cells terminally differentiated and lost tumorigenic properties by treatment with recombinant fibroblast interferon and mezerein. This approach permitted cloning of multiple genes displaying enhanced expression when melanoma cells terminally differentiated, called melanoma differentiation associated (mda) genes. One mda gene, mda-7, has risen to the top of the list based on its relevance to cancer and now inflammation and other pathological states, which based on presence of a secretory sequence, chromosomal location, and an IL-10 signature motif has been named interleukin-24 (MDA-7/IL-24). Discovered in the early 1990s, MDA-7/IL-24 has proven to be a potent, near ubiquitous cancer suppressor gene capable of inducing cancer cell death through apoptosis and toxic autophagy in cancer cells in vitro and in preclinical animal models in vivo. In addition, MDA-7/IL-24 embodied profound anticancer activity in a Phase I/II clinical trial following direct injection with an adenovirus (Ad.mda-7; INGN-241) in tumors in patients with advanced cancers. In multiple independent studies, MDA-7/IL-24 has been implicated in many pathological states involving inflammation and may play a role in inflammatory bowel disease, psoriasis, cardiovascular disease, rheumatoid arthritis, tuberculosis, and viral infection. This review provides an up-to-date review on the multifunctional gene mda-7/IL-24, which may hold potential for the therapy of not only cancer, but also other pathological states.

Synergistic effect between celecoxib and luteolin is dependent on estrogen receptor in human breast cancer cells

The anti-cancer effects of celecoxib and luteolin are well known. Although our previous study demonstrated that the combination of celecoxib and luteolin synergistically inhibits breast tumor growth compared with each of the treatments alone, we did not uncover the molecular mechanisms of these effects. The aims of our present study were to compare the effects of a celecoxib and luteolin combination treatment in four different human breast cell lines and to determine the mechanisms of action in vitro and in vivo. The synergistic effects of a celecoxib and luteolin combination treatment yielded significantly greater cell growth inhibition in all four breast cancer cell lines compared with the single agents alone. In particular, combined celecoxib and luteolin treatment significantly decreased the growth of MDA-MB-231 cancer cells in vivo compared with either agent alone. The celecoxib and luteolin combination treatment induced synergistic effects via Akt inactivation and extracellular signal-regulated kinase (ERK) signaling inhibition in MCF-7 and MCF7/HER18 cells and via Akt inactivation and ERK signaling activation in MDA-MB-231 and SkBr3 cells. These results demonstrate the synergistic anti-tumor effect of the celecoxib and luteolin combination treatment in different four breast cancer cell lines, thus introducing the possibility of this combination as a new treatment modality.

Molecular targets and signaling pathways regulated by interleukin (IL)-24 in mediating its antitumor activities

Cancer remains a major health issue in the world and the effectiveness of current therapies is limited resulting in disease recurrence and resistance to therapy. Therefore to overcome disease recurrence and have improved treatment efficacy there is a continued effort to develop and test new anticancer drugs that are natural or synthetic - (conventional chemotherapeutics, small molecule inhibitors) and biologic (antibody, tumor suppressor genes, oligonucleotide) product. In parallel, efforts for identifying molecular targets and signaling pathways to which cancer cells are "addicted" are underway. By inhibiting critical signaling pathways that is crucial for cancer cell survival, it is expected that the cancer cells will undergo a withdrawal symptom akin to "de-addiction" resulting in cell death. Thus, the key for having an improved and greater control on tumor growth and metastasis is to develop a therapeutic that is able to kill tumor cells efficiently by modulating critical signaling pathways on which cancer cells rely for their survival.Currently several small molecule inhibitors targeted towards unique molecular signaling pathways have been developed and tested in the clinic. Few of these inhibitors have shown efficacy while others have failed. Thus, targeting a single molecule or pathway may be insufficient to completely block cancer cell proliferation and survival. It is therefore important to identify and test an anticancer drug that can inhibit multiple signaling pathways in a cancer cell, control growth of both primary and metastatic tumors and is safe.One biologic agent that has the characteristics of serving as a potent anticancer drug is interleukin (IL)-24. IL-24 suppresses multiple signaling pathways in a broad-spectrum of human cancer cells leading to tumor cell death, inhibition of tumor angiogenesis and metastasis. Additionally, combining IL-24 with other therapies demonstrated additive to synergistic antitumor activity. Clinical testing of IL-24 as a gene-based therapeutic for the treatment of solid tumors demonstrated that IL-24 is efficacious and is safe. The unique features of IL-24 support its further development as an anticancer drug for cancer treatment.In this review we summarize the current understanding on the molecular targets and signaling pathways regulated by IL-24 in mediating its anticancer activity.

Targeting breast cancer-initiating/stem cells with melanoma differentiation-associated gene-7/interleukin-24

Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) displays a broad range of antitumor properties including cancer-specific induction of apoptosis, inhibition of tumor angiogenesis and modulation of antitumor immune responses. In our study, we elucidated the role of MDA-7/IL-24 in inhibiting growth of breast cancer-initiating/stem cells. Ad.mda-7 infection decreased proliferation of breast cancer-initiating/stem cells without affecting normal breast stem cells. Ad.mda-7 induced apoptosis and endoplasmic reticulum stress in breast cancer-initiating/stem cells similar to unsorted breast cancer cells and inhibited the self-renewal property of breast cancer-initiating/stem cells by suppressing Wnt/β-catenin signaling. Prevention of inhibition of Wnt signaling by LiCl increased cell survival upon Ad.mda-7 treatment, suggesting that Wnt signaling inhibition might play a key role in MDA-7/IL-24-mediated death of breast cancer-initiating/stem cells. In a nude mouse subcutaneous xenograft model, Ad.mda-7 injection profoundly inhibited growth of tumors generated from breast cancer-initiating/stem cells and also exerted a potent "bystander" activity inhibiting growth of distant uninjected tumors. Further studies revealed that tumor growth inhibition by Ad.mda-7 was associated with a decrease in proliferation and angiogenesis, two intrinsic features of MDA-7/IL-24, and a reduction in vivo in the percentage of breast cancer-initiating/stem cells. Our findings demonstrate that MDA-7/IL-24 is not only nontoxic to normal cells and normal stem cells but also can kill both unsorted cancer cells and enriched populations of cancer-initiating/stem cells, providing further documentation that MDA-7/IL-24 might be a safe and effective way to eradicate cancers and also potentially establish disease-free survival.

Synergistic apoptotic effect of celecoxib and luteolin on breast cancer cells

Breast cancer is heterogeneous and often hormone-dependent. There are many breast cancer treatment options, including endocrine therapy, chemotherapy, radiotherapy and targeted therapy. Unfortunately, not all patients respond to first-line treatments, and others will eventually relapse despite an initial response. Therapeutic options for these patients are limited. In the past decade, several studies have demonstrated the antitumor effect of celecoxib and luteolin in breast cancer as single treatment. The effect of combination treatment of celecoxib and luteolin in human breast cancer cells has not been well characterized. The present study examined the synergistic effect of celecoxib and luteolin on the human breast cancer cell lines MCF-7 and MDA-MB-231. We analyzed cell proliferation, cell death, apoptosis and changes in protein expression by performing cell survival assays, apoptosis assays and western blotting. The combination treatment significantly decreased cancer cell viability, and it had a greater efficiency in killing tumor cells after 72 h of treatment, compared to treatment with either agent alone or the control in a concentration- and time-dependent manner (P=0.01). The combination treatment demonstrated a greater than additive increase in breast cancer cell apoptosis (P=0.01). Decreased levels of Akt phosphorylation (pAkt) were noted after celecoxib and luteolin combination treatment. The combination of celecoxib and luteolin provided superior inhibition of breast cancer cell growth than either celecoxib or luteolin treatment alone. These results suggest that celecoxib and luteolin combination may be a new possible treatment option for breast cancer.

The non-steroidal anti-inflammatory drugs Sulindac sulfide and Diclofenac induce apoptosis and differentiation in human acute myeloid leukemia cells through an AP-1 dependent pathway

Acute myeloid leukemia is a heterogeneous disease with varying genetic and molecular pathologies. Non-steroidal anti-inflammatory drugs (NSAIDs) have been proven to possess significant anti-proliferative potential in various cancer cells in vitro and in vivo. Hence, treatment with these agents can be utilized to study disease specific anti-proliferative pathways. In this study, a total number of 42 bone marrow derived CD34(+) selected de novo AML patient samples and the AML cell lines THP-1 and HL-60 were treated with the NSAIDs Sulindac sulfide and Diclofenac. We analyzed viability, apoptosis, differentiation and addressed the molecular mechanisms involved. We found a consistent induction of apoptosis and to some extent an increased myeloid differentiation capacity in NSAID treated AML cells. Comprehensive protein and gene expression profiling of Diclofenac treated AML cells revealed transcriptional activation of GADD45α and its downstream MAPK/JNK pathway as well as increased protein levels of the caspase-3 precursor. This pointed towards a role of the c-Jun NH(2)-terminal kinase (JNK) in NSAID mediated apoptosis that we found indeed to be dependent on JNK activity as addition of a specific JNK-inhibitor abrogated apoptosis. Furthermore, the AP-1 transcription factor family members' c-Jun, JunB and Fra-2 were transcriptionally activated in NSAID treated AML cells and re-expression of these transcription factors led to activation of GADD45α with induction of apoptosis. Mechanistically, we demonstrate that NSAIDs induce apoptosis in AML through a novel pathway involving increased expression of AP-1 heterodimers, which by itself is sufficient to induce GADD45α expression with consecutive activation of JNK and induction of apoptosis.

mda-7/IL-24: a unique member of the IL-10 gene family promoting cancer-targeted toxicity

Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24) is a unique member of the IL-10 gene family that displays nearly ubiquitous cancer-specific toxicity, with no harmful effects toward normal cells or tissues. mda-7/IL-24 was cloned from human melanoma cells by differentiation induction subtraction hybridization (DISH) and promotes endoplasmic reticulum (ER) stress culminating in apoptosis or toxic autophagy in a broad-spectrum of human cancers, when assayed in cell culture, in vivo in human tumor xenograft mouse models and in a Phase I clinical trial in patients with advanced cancers. This therapeutically active cytokine also induces indirect antitumor activity through inhibition of angiogenesis, stimulation of an antitumor immune response, and sensitization of cancer cells to radiation-, chemotherapy- and antibody-induced killing.

Tumour suppressor function of MDA-7/IL-24 in human breast cancer

Introduction

Melanoma differentiation associated gene-7 (MDA-7), also known as interleukin (IL)-24, is a tumour suppressor gene associated with differentiation, growth and apoptosis. However, the mechanisms underlying its anti-neoplastic activity, tumour-specificity and efficacy across a spectrum of human cancers have yet to be fully elucidated. In this study, the biological impact of MDA-7 on the behavior of breast cancer (BC) cells is evaluated. Furthermore, mRNA expression of MDA-7 is assessed in a cohort of women with BC and correlated with established pathological parameters and clinical outcome.

Methods

The human BC cell line MDA MB-231 was used to evaluate the in-vitro impact of recombinant human (rh)-MDA-7 on cell growth and motility, using a growth assay, wounding assay and electric cell impedance sensing (ECIS). Localisation of MDA-7 in mammary tissues was assessed with standard immuno-histochemical methodology. BC tissues (n = 127) and normal tissues (n = 33) underwent RNA extraction and reverse transcription, MDA-7 transcript levels were determined using real-time quantitative PCR. Transcript levels were analyzed against tumour size, grade, oestrogen receptor (ER) status, nodal involvement, TNM stage, Nottingham Prognostic Index (NPI) and clinical outcome over a 10 year follow-up period.

Results

Exposure to rh-MDA-7 significantly reduced wound closure rates for human BC cells in-vitro. The ECIS model demonstrated a significantly reduced motility and migration following rh-MDA-7 treatment (p = 0.024). Exposure to rh-MDA-7 was only found to exert a marginal effect on growth. Immuno-histochemical staining of human breast tissues revealed substantially greater MDA-7 positivity in normal compared to cancer cells. Significantly lower MDA-7 transcript levels were identified in those predicted to have a poorer prognosis by the NPI (p = 0.049) and those with node positive tumours. Significantly lower expression was also noted in tumours from patients who died of BC compared to those who remained disease free (p = 0.035). Low levels of MDA-7 were significantly correlated with a shorter disease free survival (mean = 121.7 vs. 140.4 months, p = 0.0287) on Kaplan-Meier survival analysis.

Conclusion

MDA-7 significantly inhibits the motility and migration of human BC cells in-vitro. MDA-7 expression is substantially reduced in malignant breast tissue and low transcript levels are significantly associated with unfavourable pathological parameters, including nodal positivity; and adverse clinical outcomes including poor prognosis and shorter disease free survival. MDA-7 offers utility as a prognostic marker and potential for future therapeutic strategies.

Differential subcellular expression of protein kinase C betaII in breast cancer: correlation with breast cancer subtypes

Protein kinase C betaII (PKCβII) represents a novel potential target for anticancer therapies in breast cancer. In order to identify patient subgroups which might benefit from PKC-targeting therapies, we investigated the expression of PKCβII in human breast cancer cell lines and in a tissue microarray (TMA). We first screened breast cancer cell line representatives of breast cancer subtypes for PKCβII expression at the mRNA and at the protein levels. We analyzed a TMA comprising of tumors from 438 patients with a median followup of 15.4 years for PKCβII expression by immunohistochemistry along with other prognostic factors in breast cancer. Among a panel of human breast cancer cell lines, only MDA-MB-436, a triple negative basal cell line, showed overexpression for PKCβII both at the mRNA and at the protein levels. In breast cancer patients, cytoplasmic expression of PKCβII correlated positively with human epidermal growth factor receptor-2 (HER-2; P = 0.01) and Ki-67 (P = 0.016), while nuclear PKCβII correlated positively with estrogen receptor (ER; P = 0.016). The positive correlation of CK5/6 with cytoplasmic PKCβII (P = 0.033) lost statistical significance after adjusting for multiple comparisons (P = 0.198). Cytoplasmic PKCβII did not correlate with cyclooxygenase (COX-2; P = 0.925) and vascular endothelial growth factor (P = 1). There was no significant association between PKCβII staining and overall survival. Cytoplasmic PKCβII correlates with HER-2 and Ki-67, while nuclear PKCβII correlates with ER in breast cancer. Our study suggests the necessity for assessing the subcellular localization of PKCβII in breast cancer subtypes when evaluating the possible effectiveness of PKCβII-targeting agents.

The level of ATP analog and isopentenyl pyrophosphate correlates with zoledronic acid-induced apoptosis in cancer cells in vitro

Bisphosphonates are potent inhibitors of osteoclast function widely used to treat excessive bone resorption associated, e.g., with bone metastases. They have also antitumor activity. However, it is unclear whether this reflects an indirect effect via inhibition of bone resorption or a direct antitumor effect. Nitrogen-containing bisphosphonates (N-BPs), including zoledronic acid (ZOL), act by inhibiting farnesyl pyrophosphate synthase (FPPS). The mevalonate pathway is blocked and the accumulation of isopentenyl pyrophosphate (IPP) consequently occurs. IPP is conjugated to AMP to form a novel ATP analog (ApppI). The present study was undertaken to clarify whether IPP and/or ApppI has a direct involvement in apoptosis caused by ZOL in different cancer cell lines. There are marked differences in ZOL-induced ApppI formation between different cancer cell lines. On this basis, we selected three cancer cell lines that differ significantly from each other in their ZOL-induced IPP and ApppI accumulation: human estrogen-dependent (MCF7) and estrogen-independent (MDA-MB 436) breast cancer cell lines and a human myeloma cell line (RPMI 8226). The amount of IPP/ApppI correlated with the capacity of cells to undergo apoptosis. Geranylgeraniol (GGOH), an intermediate of mevalonate metabolism, blocks both IPP and ApppI formation and to some degree ZOL-induced apoptosis in a cell line-dependent manner. In addition, lovastatin (LOV), an inhibitor of the enzyme HMGCoA reductase, completely blocks IPP/ApppI formation as determined by mass spectrometry analysis, but enhances apoptosis. In conclusion, the current data suggest that ZOL-induced IPP/ApppI formation can contribute to ZOL-induced apoptosis. This mechanism and the inhibition of protein prenylation, both outcomes of FPPS inhibition in mevalonate pathway, seem to act in concert in ZOL-induced apoptosis in cancer cells.

Targeted combinatorial therapy of non-small cell lung carcinoma using a GST-fusion protein of full-length or truncated MDA-7/IL-24 with Tarceva

Melanoma differentiation associated gene-7/interleukin-24 (mda-7/IL-24), a cytokine belonging to the IL-10 family, displays cancer-specific apoptosis-inducing properties when delivered by a replication-incompetent adenovirus (Ad.mda-7) or as a GST-tagged recombinant protein (GST-MDA-7). Previous studies demonstrated that an adenovirus expressing M4, a truncated version of MDA-7/IL-24 containing amino acid residues 104-206, also induced similar cancer-specific apoptosis. We generated recombinant GST-M4 proteins and examined the potency of GST-MDA-7 and GST-M4 on a panel of epidermal growth factor receptor (EGFR) wild type and mutant non-small cell lung carcinoma (NSCLC) cells either as a single agent or in combination with a reversible EGFR inhibitor, Tarceva. The combination of either GST-MDA-7 or GST-M4 ( approximately 0.1 microM) and Tarceva (10 microM), at sub-optimal apoptosis-inducing concentrations synergistically enhanced growth inhibition and apoptosis induction over that observed with either agent alone. The combination treatment also augmented inhibition of EGFR signaling, analyzed by phosphorylation of EGFR and its downstream effectors AKT and ERK1/2, over that with single-agent therapy. Tarceva enhanced GST-MDA-7 and GST-M4 toxicity in cells expressing mutated EGFR proteins that are resistant to the inhibitory effects of Tarceva. In total, these data suggest that combined treatment of NSCLC cells with an EGFR inhibitor can augment the efficacy of GST-MDA-7 and GST-M4 and that the EGFR inhibitor Tarceva may mediate this combinatorial effect by inhibiting multiple tyrosine kinases in addition to the EGFR. This approach highlights a potential new combinatorial strategy, which may prove beneficial for NSCLC patients with acquired resistance to EGFR inhibitors.

Phospholipase A2 as targets for anti-cancer drugs

Phospholipase A(2) (PLA(2)) are esterases that cleave glycerophospholipids to release fatty acids and lysophospholipids. Inhibition of PLA(2) alters cancer cell growth and death in vitro and PLA(2) expression is increased in breast, lung, and prostate cancers compared to control tissues. Thus, PLA(2) may be novel targets for chemotherapeutics. However, PLA(2) are a diverse family of enzymes, encompassing 19 members. The selectivity of these individual PLA(2) for phospholipids varies, as does their location within the cell, and tissue expression. Thus, their role in cancer may also vary. This review summarizes the expression of individual PLA(2) in cancers, focuses on the potential mechanisms by which these esterases mediate carcinogenesis, and suggests that select PLA(2) isoforms may be targets for anti-cancer drugs.

Inhibition of nuclear factor-κB augments antitumor activity of adenovirus-mediated melanoma differentiation-associated gene-7 against lung cancer cells via mitogen-activated protein kinase kinase kinase 1 activation

Nuclear factor-kappaB (NF-kappaB) activation promotes cell survival and growth. Reports show that chemotherapeutic agents and cytokines that are used for cancer therapy activate NF-kappaB expression in tumor cells and its suppression enhanced the antitumor activity. We hypothesized that adenovirus-mediated overexpression of melanoma differentiation-associated gene-7/interleukin-24 (Ad-mda7/IL-24) induces NF-kappaB expression and that inhibition of this expression results in enhanced tumor cell killing. Treatment of human lung tumor (H1299 and A549) cells with Ad-mda7 resulted in NF-kappaB activation in a dose- and time-dependent manner before activation of cell death pathways. To establish that inhibition of Ad-mda7-mediated NF-kappaB activation results in enhanced tumor cell killing, H1299 cells that overexpress the dominant-negative I kappa B alpha (dnI kappa B alpha) were treated with Ad-mda7 in vitro. An enhanced growth arrest and apoptosis was observed in Ad-mda7-treated H1299-dnI kappa B alpha compared with H1299-Neo cells. This Ad-mda7-mediated enhanced killing of H1299-dnI kappa B alpha cells involved cleavage of mitogen-activated protein kinase kinase kinase 1 (MEKK1) and caspase-3 in a feedback loop mechanism. The inhibition of MEKK1 or caspase-3 cleavage in H1299-dnI kappa B alpha cells resulted in reduced Ad-mda7-mediated cell killing. In vivo, the treatment of H1299-dnI kappa B alpha s.c. tumors with Ad-mda7 resulted in increased drug sensitivity and delayed the tumor growth rate compared with Ad-mda7-treated H1299-Neo tumors. Molecular analysis of Ad-mda7-treated H1299-dnI kappa B alpha tumors showed increased MEKK1 cleavage and activation of caspase-3 compared with Ad-mda7-treated H1299-Neo tumors. Our findings thus showed that the NF-kappaB activation induced by Ad-mda7 treatment of lung cancer cells is an intrinsic survival mechanism and that the inhibition of this NF-kappaB expression results in enhanced tumor cell killing.

Expression, purification, and characterization of recombinant human interleukin 24 in Escherichia coli

Interleukin-24 (IL-24) can induce apoptosis of a broad range of tumor cells, and this function of IL-24 is independent of classic tumor suppressor genes, such as p53, Rb and p16. Here, we report the expression, purification and preparation of a recombinant IL-24 protein (rIL-24) without post-translational modifications, which may selectively induce apoptosis of tumor cells in vitro. We found that non-fusion rIL-24 was not able to be expressed by vectors pET11c, 28a, and 22b in Escherichia coli. To obtain recombinant non-fusion IL-24 protein, the encoding region for IL-24 was cloned between KpnI and BamHI in pET32a. The Trx (Thioredoxin)/IL-24 fusion proteins were expressed in the form of inclusion bodies in E. coli host strain BL21 (DE21). The expression level was more than 30% of total cell lysate. Inclusion bodies were disrupted, washed, and isolated at pH 9.0, and were completely dissolved in a buffer containing 2M urea at pH 9.0. After nickel ion metal affinity chromatography, gel filtration chromatography, and renaturation, the refolded fusion proteins with a purity of >96% were obtained. Trx/IL-24 proteins were digested by enterokinase (EK) to both Trx and rIL-24 fragments which then were separated by cation exchange chromatography. Cell proliferation experiments proved that the rIL-24 (98% purity) retains its cancer-selective apoptosis-inducing properties. This result suggested that the rIL-24 may have cancer therapeutic applications.