Gene Therapy with Secretory Leukoprotease Inhibitor Promoter-Controlled Replication-Competent Adenovirus for Non-Small Cell Lung Cancer

Applications of tissue-specific and cancer-selective gene promoters for cancer diagnosis and therapy

Current treatment of solid tumors with standard of care chemotherapies, radiation therapy and/or immunotherapies are often limited by severe adverse toxic effects, resulting in a narrow therapeutic index. Cancer gene therapy represents a targeted approach that in principle could significantly reduce undesirable side effects in normal tissues while significantly inhibiting tumor growth and progression. To be effective, this strategy requires a clear understanding of the molecular biology of cancer development and evolution and developing biological vectors that can serve as vehicles to target cancer cells. The advent and fine tuning of omics technologies that permit the collective and spatial recognition of genes (genomics), mRNAs (transcriptomics), proteins (proteomics), metabolites (metabolomics), epiomics (epigenomics, epitranscriptomics, and epiproteomics), and their interactomics in defined complex biological samples provide a roadmap for identifying crucial targets of relevance to the cancer paradigm. Combining these strategies with identified genetic elements that control target gene expression uncovers significant opportunities for developing guided gene-based therapeutics for cancer. The purpose of this review is to overview the current state and potential limitations in developing gene promoter-directed targeted expression of key genes and highlights their potential applications in cancer gene therapy.

Targeting stanniocalcin-1-expressing tumor cells elicits efficient antitumor effects in a mouse model of human lung cancer

Lung cancer is the most common cause of cancer‐related death in developed countries; therefore, the generation of effective targeted therapeutic regimens is essential. Recently, gene therapy approaches toward malignant cells have emerged as attractive molecular therapeutics. Previous studies have indicated that stanniocalcin‐1 (STC‐1), a hormone involved in calcium and phosphate homeostasis, positively regulates proliferation, apoptosis resistance, and glucose metabolism in lung cancer cell lines. In this study, we investigated if targeting STC‐1 in tumor cells could be a promising strategy for lung cancer gene therapy. We confirmed that STC‐1 levels in peripheral blood were higher in lung cancer patients than in healthy donors and that STC‐1 expression was observed in five out of eight lung cancer cell lines. A vector expressing a suicide gene, uracil phosphoribosyltransferase (UPRT), under the control of the STC‐1 promoter, was constructed (pP_STC‐1‐UPRT) and transfected into three STC‐1‐positive cell lines, PC‐9, A549, and H1299. When stably transfected, we observed significant cell growth inhibition using 5‐fluorouracil (5‐FU) treatment. Furthermore, growth of the STC‐1‐negative lung cancer cell line, LK‐2 was significantly arrested when combined with STC‐1‐positive cells transfected with pP_STC‐1‐UPRT.

We believe that conferring cytotoxicity in STC‐1‐positive lung cancer cells using a suicide gene may be a useful therapeutic strategy for lung cancer.

microRNA-539 functions as a tumor suppressor in papillary thyroid carcinoma via the transforming growth factor β1/Smads signaling pathway by targeting secretory leukocyte protease inhibitor

Papillary thyroid carcinoma (PTC) is the most common type of thyroid malignancy, with growing incidence every year. microRNAs (miRs) are known to regulate the physiological and pathological processes of cancers, such as proliferation, migration, invasion, survival, and epithelial-mesenchymal transition (EMT). Herein, this study aimed to investigate the effect of miR-539 on cell proliferation, apoptosis, and EMT by targeting secretory leukocyte protease inhibitor (SLPI) via the transforming growth factor β1 (TGF-β1)/Smads signaling pathway in PTC. First, PTC-related differentially expressed genes and regulatory miR were screened using bioinformatics analysis, dual luciferase reporter gene assay, and ribonucleoprotein immunoprecipitation, which identified the SLPI gene and the regulatory miR-539 for this study. We identified SLPI as a highly expressed gene in PTC tissues, and SLPI was targeted and negatively regulated by miR-539. Then, we introduced a series of miR-539 mimics, miR-539 inhibitors, and small interfering RNA against SLPI plasmids into CGTHW-3 cells to examine the effects of miR-539 and SLPI on the expression of TGF-β1/Smads signaling pathway-, EMT-, and apoptosis-related factors, as well as cell proliferation, migration, invasion, and apoptosis. The obtained results indicated that CGTHW-3 cells treated with silenced SLPI or overexpressed miR-539 suppressed the cell proliferation, migration, invasion abilities, and resistance to apoptosis of PTC cells, corresponding to increased expression of Bcl-2-associated X protein, TGF-β1, Sekelsky mothers against dpp 4, and epithelial cadherin, and decreased B cell lymphoma 2, Vimentin, and N-cadherin. Altogether, we concluded that overexpressed miR-539 could inhibit the PTC cell proliferation and promote apoptosis and EMT by targeting SPLI via activation of the TGF-β1/Smads signaling pathway.

PKM1 Confers Metabolic Advantages and Promotes Cell-Autonomous Tumor Cell Growth

Expression of PKM2, which diverts glucose-derived carbon from catabolic to biosynthetic pathways, is a hallmark of cancer. However, PKM2 function in tumorigenesis remains controversial. Here, we show that, when expressed rather than PKM2, the PKM isoform PKM1 exhibits a tumor-promoting function in KRASG12D-induced or carcinogen-initiated mouse models or in some human cancers. Analysis of Pkm mutant mouse lines expressing specific PKM isoforms established that PKM1 boosts tumor growth cell intrinsically. PKM1 activated glucose catabolism and stimulated autophagy/mitophagy, favoring malignancy. Importantly, we observed that pulmonary neuroendocrine tumors (NETs), including small-cell lung cancer (SCLC), express PKM1, and that PKM1 expression is required for SCLC cell proliferation. Our findings provide a rationale for targeting PKM1 therapeutically in certain cancer subtypes, including pulmonary NETs.

Targeted gene therapy of the HSV-TK/hIL-12 fusion gene controlled by the hSLPI gene promoter of human non-small cell lung cancer in vitro

The incidence of lung cancer and lung cancer-associated mortality have markedly increased worldwide, and gene-targeted therapy has emerged as a promising treatment strategy. The present study aimed to explore the targeted antitumor effect of the herpes simplex virus-thymidine kinase/human interleukin-12 (HSV-TK/hIL-12) fusion gene regulated by the human secretory leukocyte protease inhibitor (hSLPI) promoter of human non-small cell lung cancer (hNSCLC). There were four recombinant eukaryotic expression vectors: pcDNA3.1-CMV-TK, pcDNA3.1-CMV-TK/hIL-12, pcDNA3.1-phSLP-TK and pcDNA3.1-phSLP-TK/hIL-12. These were constructed and transfected into the A549, SPC-A1 and HepG2 cell lines in vitro. The expression of the HSV-TK/hIL-12 fusion gene was detected with reverse transcription-polymerase chain reaction (RT-PCR), and the content of hIL-12 was measured using an ELISA. The antitumor effect of the fusion gene on the A549, SPC-A1 and HepG2 cell lines was determined using an MTT assay. Analysis of the experimental data demonstrated that genes regulated by the cytomegalovirus promoter were expressed at the same level in three different tumor cell lines. Genes regulated by the hSLPI promoter were expressed in the A549 and SPC-A1 cell lines, but not in the HepG2 cell line. Coincidentally, the hIL-12 expression levels were similar to those observed in previous RT-PCR findings. In the Pcmv-TK/Pcmv-TK-hIL-12 group for all three cell lines, as well as in the PSLPI-TK/PSLPI-TK-hIL-12 group for the A549 and SPC-A1 cell lines, the cell survival rate declined significantly and the fusion gene transfection group indicated a lower cell survival rate, when compared with single gene transfection group. The present study indicated that the fusion gene regulated by the hSLPI promoter had a targeted antitumor effect on hNSCLC, and that the combined suicide gene and immune gene therapy had a stronger antitumor effect, compared with single gene therapy.

Antitumor Efficacy of SLPI Promoter-Controlled Expression of Artificial microRNA Targeting EGFR in a Squamous Cell Carcinoma Cell Line

The purpose of this study was to develop a recombinant adenovirus with secretory leukoprotease inhibitor (SLPI) promoter-controlled expression for gene therapy of squamous cell carcinoma (SCC). An artificial microRNA targeting epidermal growth factor receptor (EGFR) was designed, and used to construct a replication-defective recombinant adenovirus with SLPI promoter-controlled expression. The silencing efficiency of this vector (Ad-SLPI-EGFRamiR) was detected in Hep-2 cells. Western blotting showed that the expression of 170 kD EGFR was significantly reduced in Hep-2 cells 72 h after infection with Ad-SLPI-EGFRamiR. At a multiplicity of infection (MOI) of 200 pfu/cell, proliferation of Hep-2 cells was highly inhibited by Ad-SLPI-EGFRamiR (inhibition rate: ~70%). The apoptosis rate of Hep-2 cells at 72 h after infection with Ad-SLPI-EGFRamiR at a MOI 35 pfu/cell was 32.8%. The adenovirus constructed was able to specifically inhibit the growth of SCC cells in vitro.

Secretory leukocyte protease inhibitor modulates urethane-induced lung carcinogenesis

Secretory leukocyte protease inhibitor (SLPI), 11.7 kDa serine protease inhibitor, is produced primarily in the respiratory tract, but it is often elevated in lung, head/neck and ovarian cancers. SLPI expression in relation to cancer progression, metastasis and invasion has been studied extensively in non-small cell lung cancer. However, the role of SLPI during the early stages of carcinogenesis remains unknown. We hypothesized that SLPI is required from the initiation and promotion to the progression of lung carcinogenesis. A skin allograft model using SLPI-knockout (SLPI-KO) mice and short hairpin RNA-treated cells was used to demonstrate that SLPI expression in tumor cells is crucial for tumor formation. Moreover, lung tumorigenesis induced by urethane, a chemical lung carcinogen, was significantly suppressed in SLPI-KO mice in association with decreased nuclear factor-kappaB (NF-κB) activity. SLPI deficiency also resulted in decreased cell numbers and decreased production of inflammatory cytokines in bronchoalveolar lavage fluids. The suppression of NF-κB activation in SLPI-KO mice was associated with lower expression of NF-κB-related survival genes and DNA repair genes. Our findings demonstrate that SLPI plays an important role from the initial stages of lung carcinogenesis to the progression of lung cancer in an NF-κB-dependent manner.

Targeting cancer by transcriptional control in cancer gene therapy and viral oncolysis

Cancer-specificity is the key requirement for a drug or treatment regimen to be effective against malignant disease--and has rarely been achieved adequately to date. Therefore, targeting strategies need to be implemented for future therapies to ensure efficient activity at the site of patients' tumors or metastases without causing intolerable side-effects. Gene therapy and viral oncolysis represent treatment modalities that offer unique opportunities for tumor targeting. This is because both the transfer of genes with anti-cancer activity and viral replication-induced cell killing, respectively, facilitate the incorporation of multiple mechanisms restricting their activity to cancer. To this end, cellular mechanisms of gene regulation have been successfully exploited to direct therapeutic gene expression and viral cell lysis to cancer cells. Here, transcriptional targeting has been the role model and most widely investigated. This approach exploits cellular gene regulatory elements that mediate cell type-specific transcription to restrict the expression of therapeutic genes or essential viral genes, ideally to cancer cells. In this review, we first discuss the rationale for such promoter targeting and its limitations. We then give an overview how tissue-/tumor-specific promoters are being identified and characterized. Strategies to apply and optimize such promoters for the engineering of targeted viral gene transfer vectors and oncolytic viruses-with respect to promoter size, selectivity and activity in the context of viral genomes-are described. Finally, we discuss in more detail individual examples for transcriptionally targeted virus drugs. First highlighting oncolytic viruses targeted by prostate-specific promoters and by the telomerase promoter as representatives of tissue-targeted and pan-cancer-specific virus drugs respectively, and secondly recent developments of the last two years.

Hepatocyte growth factor and Met in tumor biology and therapeutic approach with NK4

Hepatocyte growth factor (HGF) and Met/HGF receptor tyrosine kinase play a role in the progression to invasive and metastatic cancers. A variety of cancer cells secrete molecules that enhance HGF expression in stromal fibroblasts, while fibroblast-derived HGF, in turn, is a potent stimulator of the invasion of cancer cells. In addition to the ligand-dependent activation, Met receptor activation is negatively regulated by cell-cell contact and Ser985 phosphorylation in the juxtamembrane of Met. The loss of intercellular junctions may facilitate an escape from the cell-cell contact-dependent suppression of Met-signaling. Significance of juxtamembrane mutations found in human cancers is assumed to be a loss-of-function in the negative regulation of Met. In attempts to block the malignant behavior of cancers, NK4 was isolated as a competitive antagonist against HGF-Met signaling. Independently on its HGF-antagonist action, NK4 inhibited angiogenesis induced by vascular endothelial cell growth factor and basic fibroblast growth factor, as well as HGF. In experimental models of distinct types of cancers, NK4 inhibited Met activation and this was associated with inhibition of tumor invasion and metastasis. NK4 inhibited tumor angiogenesis, thereby suppressing angiogenesis-dependent tumor growth. Cancer treatment with NK4 suppresses malignant tumors to be "static" in both tumor growth and spreading.

Secretory leukocyte peptidase inhibitor and lung cancer

Secretory leukocyte peptidase inhibitor (SLPI) belongs to the whey acidic protein four-disulfide core family of proteins, and has antimicrobial and antiprotease functions. SLPI is produced by the epithelial cells lining the respiratory, digestive, and reproductive tracts. Gene-targeting experiments in mice indicated that one function of SLPI is to protect proepithelin from elastase cleavage in wound healing. In addition to its antiprotease function, SLPI has an anti-inflammatory function through the modulation of nuclear factor-kappaB acting intracellularly, especially in macrophages. SLPI is also produced in cancer tissues, but its role in cancer is not well understood. SLPI genes are often upregulated under tumorigenic conditions. We found a negligible number of tumors in the lungs of SLPI knockout mice 20 or 40 weeks after administration of urethane, an interesting experimental model for investigating the function of SLPI in cancer. This review discusses the normal function of SLPI and its possible roles in cancer tissues.

Inhibition of angiogenesis and HGF-cMET-elicited malignant processes in human hepatocellular carcinoma cells using adenoviral vector-mediated NK4 gene therapy

NK4 is an hepatocyte growth factor (HGF)-antagonist and a broad angiogenesis inhibitor. NK4 gene therapy has confirmed antitumor efficacy on cancers with intact HGF-cMET signaling pathway. However, the feasibility to treat tumors in which the effect of the HGF-cMET signaling pathway is less unambiguous or may even be inhibitory on carcinogenesis, such as hepatocellular carcinoma (HCC) with NK4 needs further assessment. Therefore, we evaluated the effects of adenoviral vector-mediated expression of NK4 on the biological behavior of a series of HCC cell lines in vitro and on HepG2 xenografts in vivo. In vitro, transduction of HCC cell lines with the replication-deficient recombinant adenoviral vector AdCMV.NK4 resulted in significant inhibition of proliferation over and above the antimitogenic effects of HGF. In addition, HGF-induced scattering and invasion through matrigel were inhibited effectively. Moreover, transduced HCC cells produced sufficient amounts of NK4 protein to achieve bystander effects involving reduced migration of nontransduced tumor cells and reduced proliferation of endothelial cells. Finally, treatment of established HepG2 xenografts with AdCMV.NK4 resulted in significant tumor growth delay and significant reduction of intratumoral microvessel density. In conclusion, NK4 gene therapy is a promising strategy to treat HCC based on the pleiotropic functions of NK4 interfering with tumor growth, invasion, metastasis and angiogenesis.

Eukaryotic expression vectors and immunoconjugates for cancer therapy

This review considers ways to address specificity to therapeutic targeted anticancer agents. These include transcriptional activation of tissue- and tumor-specific promoters in eukaryotic expression vectors and use of antitumor-directed immunoconjugates. The review deals with analysis of strategies used for selection of targeted promoters and examples of antibody fusion proteins exhibiting antitumor activity. A new direction in antitumor treatment pooling together methods of gene therapy and antibody therapy has appeared. This direction is based on the development of vectors encoding secreted forms of immunoconjugates. After vector introduction into a cell, the latter is capable of synthesizing and secreting antibody fusion protein composed of a therapeutic anticancer agent and antibody specifically targeted to cancer cells.

Proteins with whey-acidic-protein motifs and cancer

The importance of early diagnosis to reduce the morbidity and mortality from cancer has led to a search for new sensitive and specific tumour markers. Molecular techniques developed over the past few years allow simultaneous screening of thousands of genes, and have been applied to different cancers to identify many genes that are modulated in various cancers. Of these, attention has focused on genes coding for a family of proteins with whey-acidic-protein (WAP) motifs. Most notably, the genes coding for elafin, antileukoproteinase 1 (previously called secretory leucocyte proteinase inhibitor, SLPI), WAP four disulphide core domain protein 1 (previously called prostate stromal protein 20 kDa, PS20), and WAP four disulphide core domain protein 2 (previously called major human epididymis-specific protein E4, HE4), have been identified as candidate molecular markers for several cancers. In this review, we assess data for an association between cancer and human WAP proteins, and discuss their potential role in tumour progression. We also propose a new mechanism by which WAP proteins might have a role in carcinogenesis.

Production and formulation of adenovirus vectors

Adenovirus vectors have attracted considerable interest over the past decade, with ongoing clinical development programs for applications ranging from replacement therapy for protein deficiencies to cancer therapeutics to prophylactic vaccines. Consequently, considerable product, process, analytical, and formulation development has been undertaken to support these programs. For example, "gutless" vectors have been developed in order to improve gene transfer capacity and durability of expression; new cell lines have been developed to minimize recombination events; production conditions have been optimized to improve volumetric productivities; analytical techniques and scaleable purification processes have advanced towards the goal of purified adenovirus becoming a "well-characterized biological"; and liquid formulations have been developed which maintain virus infectivity at 2-8 degrees C for over 18 months. These and other advances in the production of adenovirus vectors are discussed in detail in this review. In addition, the needs for the next decade are highlighted.

Cancer gene therapy

The prognosis of patients with some kinds of cancers whose patients are often found unresectable upon diagnosis is still dismal. In these fields, development of a new therapeutic modality is needed and gene therapy represents one promising strategy. So far, numerous cancer gene therapy clinical trials based on these principles have been carried out and have shown the safety of such modalities, but have fallen short of the initial expectations to cure cancers. In this review, we would like to make a problem-oriented discussion of current status of cancer gene therapy research by using mainly gastrointestinal cancers as an example. In order to overcome obstacles for full realization of cancer gene therapy, numerous researches have been conducted by many researchers. Various cancer-selective and non-selective genes, as well as lytic viruses themselves have been employed for gene therapy. In the context of gene delivery method, different kinds of viral and non-viral strategies have been utilized. In addition, surrogate assays, such as soluble markers and imaging, have been developed for safer and more informative clinical trials. Many experiments and clinical trials to date have figured out current obstacles for the realization of an effective cancer gene therapy modality. Tireless efforts to overcome such hurdles and continuous infusion of novel concepts into this field should lead to break through technologies and the cure of the patients.

Mechanisms and significance of bifunctional NK4 in cancer treatment

Based on the background that hepatocyte growth factor (HGF) and c-Met/HGF receptor tyrosine kinase play a definite role in tumor invasion and metastasis, NK4, four-kringles containing intramolecular fragment of HGF, was isolated as a competitive antagonist for the HGF-c-Met system. Independent of its HGF-antagonist action, NK4 inhibited angiogenesis induced by vascular endothelial cell growth factor and basic fibroblast growth factor, as well as HGF, indicating that NK4 is a bifunctional molecule that acts as an HGF-antagonist and angiogenesis inhibitor. Interestingly, kringle domains in distinct types of proteins, e.g., plasminogen, prothrombin, plasminogen activators, apolipoprotein(a), and HGF, share angioinhibitory actions. In experimental models of distinct types of cancers, NK4 protein administration or NK4 gene therapy inhibited tumor invasion, metastasis, and angiogenesis-dependent tumor growth. Cancer treatment with NK4 may prove to suppress malignant tumors to be 'static' in both tumor growth and spreading, as based on biological characteristics of malignant tumors.

An oncolytic conditionally replicating adenovirus for hormone-dependent and hormone-independent prostate cancer

The use of conditionally replicating adenoviruses offers an attractive complementary treatment strategy for localized prostate cancer. We have produced a replicating adenovirus, Ad[I/PPT-E1A], where E1A gene expression is controlled by a recombinant regulatory sequence designated PPT. The PPT sequence comprises a PSA enhancer, a PSMA enhancer and a T-cell receptor gamma-chain alternate reading frame protein promoter, and it is shielded from transcriptional interference from adenoviral backbone sequences by an H19 insulator. Ad[I/PPT-E1A] yields prostate-specific E1A protein expression, viral replication and cytolysis in vitro. Furthermore, Ad[I/PPT-E1A] considerably regresses the growth of subcutaneous LNCaP prostate cancer tumors in nude mice. Importantly, the viral replication and cytolytic effect of Ad[I/PPT-E1A] are independent of the testosterone levels in the prostate cancer cells. This may be beneficial in a clinical setting since many prostate cancer patients are treated with androgen withdrawal. In conclusion, Ad[I/PPT-E1A] may prove to be useful in the treatment of localized prostate cancer.

A Fiber-Modified, Secretory Leukoprotease Inhibitor Promoter-Based Conditionally Replicating Adenovirus for Treatment of Ovarian Cancer

Purpose: The use of conditionally replicating adenoviruses (CRAD) is dependent on molecular differences between tumor cells and nontumor cells. Transcriptional targeting of CRAD replication via tumor-specific promoters is an effective way to control replication regulation. Genetic fiber pseudotyping is an approach for circumventing low expression of the primary adenovirus serotype 5 (Ad5) receptor by using the distinct adenovirus serotype 3 (Ad3) receptor for entry into and subsequent killing of ovarian cancer cells.

Experimental Design: In this study, we constructed a fiber-modified CRAD containing the secretory leukoprotease inhibitor (SLPI) promoter to control viral replication via the E1A gene (Ad5/3SLPI). To evaluate the liver toxicity of chimeric 5/3 fiber-modified CRADs, we compared Ad5/3SLPI with Ad5/3Cox-2L, a CRAD with E1A under control of the Cox-2 promoter, and Ad5/3Δ24, a CRAD that replicates in cancer cells inactive in the retinoblastoma/p16 pathway by use of an in vivo hepatotoxicity model and by a model system that uses slices of human liver.

Results: We show efficient viral replication and oncolysis of Ad5/3SLPI in both multiple ovarian cancer cell lines and primary tumor cell spheroids as well as therapeutic efficacy in an orthotopic mouse model of peritoneal carcinomatosis. Ad5/3SLPI showed significantly decreased liver toxicity compared with other 5/3 fiber-modified control vectors examined.

Conclusions: In summary, Ad5/3SLPI is a promising vector candidate for treating metastatic ovarian cancer and showed robust virus replication, oncolysis, and in vivo therapeutic efficacy. Ad5/3SLPI showed comparatively low liver toxicity and therefore holds potential for patient use in the clinic.

Replacement and Suicide Gene Therapy for Targeted Treatment of Lung Cancer

Lung cancer is the leading cause of cancer-related death in the developed world; consequently, novel therapeutic strategies are in high demand. A major problem with the present treatment modalities is the lack of tumor specificity giving rise to dose-limiting toxicity and side effects. Gene therapy constitutes an experimental approach gaining increased attention as a putative future cancer therapeutic strategy. Using this strategy, cancer cytotoxicity can be obtained by replacing mutated genes with functional analogues or introducing a suicide gene into the malignant cells. Insight into the molecular biology of cancer cells has identified a number of regulatory gene sequences, which can be used to selectively activate the therapeutic gene specifically in cancer cells, thereby reducing nonspecific toxicity. Although further improvements are necessary, recent encouraging results have shown promise for future clinical application of gene therapy. This article presents an update on the experimental and clinical results obtained within the field of lung cancer gene therapy, concentrating on strategies to specifically activate expression of the therapeutic gene in cancer cells. Furthermore, status of the development of delivery vector constructs for lung cancer gene therapy will be presented.