Highly versatile cancer photoimmunotherapy using photosensitizer-conjugated avidin and biotin-conjugated targeting antibodies.

BACKGROUND: Photoimmunotherapy (PIT) employing antibody-photosensitizer conjugates is a promising treatment for cancer. However, the fixed antigen specificity severely limits the efficacy and the applicability. Here we describe a universal strategy for PIT of cancer by using a near-infrared (NIR) photosensitizer IRDye700DX-conjugated NeutrAvidin, designated as AvIR, together with various biotinylated antibodies (BioAbs) for cellular targeting. METHODS: Cytotoxicity of AvIR-mediated PIT was evaluated by fluorescence imaging and cell viability assay. Phototoxic effect on tumorigenicity was assessed by tumorsphere-formation assay and Matrigel invasion assay. Cancer stem cell-like side-population (SP) cells were identified by flow cytometry. RESULTS: CHO cells stably expressing carcinoembryonic antigen or EpCAM were pre-labeled with each BioAb for the corresponding antigen, followed by AvIR administration. NIR light irradiation specifically killed the targeted cells, but not off-targets, demonstrating that the AvIR-mediated PIT does work as expected. CSC-like subpopulation of MCF-7 cells (CD24low/CD44high) and SP of HuH-7 cells (CD133+/EpCAM+) were effectively targeted and photokilled by AvIR-PIT with anti-CD44 BioAb or anti-CD133/anti-EpCAM BioAbs, respectively. As results, the neoplastic features of the cell lines were sufficiently suppressed. Cancer-associated fibroblast (CAF)-targeted AvIR-PIT by using anti-fibroblast activation protein BioAb showed an abolishment of CAF-enhanced clonogenicity of MCF-7 cells. CONCLUSIONS: Collectively, our results demonstrate that AvIR-mediated PIT can greatly broaden the applicable range of target specificity, with feasibility of efficacious and integrative control of CSC and its microenvironment.

Association of Serum HB-EGF Value and Response to Chemotherapy in Patients with Recurrent Ovarian Cancer.

BACKGROUND/AIM: Many anticancer agents including molecularly-targeted drugs have been developed for ovarian cancer. However, the prognosis of recurrent ovarian cancer remains extremely poor. Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is reported as a rational target for ovarian cancer therapy. Moreover, serum HB-EGF expression is recognized as a biomarker in patients with primary ovarian cancer. MATERIALS AND METHODS: We analysed serum samples with recurrent ovarian cancer at the Fukuoka University Hospital from April 2009 to March 2014. To assess the clinical significance of serum HB-EGF in recurrent ovarian cancer, the association between serum HB-EGF levels and prognosis in patients with recurrent ovarian cancer was examined using ELISA. RESULTS: Patients with high serum HB-EGF expression showed a significantly poor response to second-line chemotherapeutic agents compared with patients with low HB-EGF levels. CONCLUSION: HB-EGF expression in serum may be a potential therapeutic indicator for novel HB-EGF-targeted therapy in recurrent ovarian cancer.

The Long Noncoding RNA OIP5-AS1 Is Involved in the Regulation of Cell Proliferation.

BACKGROUND/AIM: OPA-interacting protein 5 antisense transcript 1 (OIP5-AS1) is a long noncoding RNA located on human chromosome 15q15.1 and transcribed in the opposite direction to OIP5. Here, we report that OIP5-AS1 is involved in regulating cell proliferation. MATERIALS AND METHODS: HeLa cells were transfected with OIP5-AS1-targeting siRNA oligonucleotides and anti-sense oligonucleotides. The cells were harvested 72 h after transfection and subjected to quantitative reverse transcription-polymerase chain reaction (qRT-PCR), and cell-cycle and apoptosis analysis. RESULTS: OIP5-AS1 was expressed at a lower level in cells harbouring an oncogenic kirsten rat sarcoma viral oncogene homolog (K-RAS) mutation than in cells expressing wild-type K-RAS. Silencing OIP5-AS1 with siRNA oligonucleotides or anti-sense oligonucleotides reduced HeLa cell proliferation. Apoptosis and cell-cycle analysis showed that silencing OIP5-AS1 did not cause apoptosis, but did cause G2/M phase cell-cycle arrest. CONCLUSION: These results suggest that OIP5-AS1 positively regulates cell proliferation by promoting G2/M phase progression.

Enhancement of antitumor activity by using a fully human gene encoding a single-chain fragmented antibody specific for carcinoembryonic antigen.

Human leukocyte antigen and/or costimulatory molecules are frequently lacking in metastatic tumor cells, and thus tumor cells are able to escape from the immune system. Although lymphocytes with a chimeric antigen receptor (CAR) is a promising approach for overcoming this challenge in cancer immunotherapy, administration of modified T cells alone often demonstrates little efficacy in patients. Therefore, in order to enhance the antitumor activity of immune cells in the cancer microenvironment, we used lymphocytes expressing CAR in combination with a fusion protein of IL-2 that contained the single-chain fragmented antibody (scFv) specific for the carcinoembryonic antigen. Among a series of CAR constructs, with or without a spacer and the intracellular domain of CD28, the CAR construct containing CD8α, CD28, and CD3ζ most effectively activated and expressed INF-γ in CAR-bearing T cells. Furthermore, in comparison with free IL-2, the combination of peripheral blood mononuclear cells expressing CAR and the fusion protein containing IL-2 significantly enhanced the antitumor activity against MKN-45 cells, a human gastric cancer cell line. In conclusion, this novel combination therapy of CAR and a fusion protein consisting of a functional cytokine and a fully human scFv may be a promising approach for adoptive cancer immunotherapy.

Serum Heparin-binding Epidermal Growth Factor-like Growth Factor (HB-EGF) as a Biomarker for Primary Ovarian Cancer.

Ovarian cancer is the most lethal malignancy among gynaecological cancers. Although many anticancer agents have been developed for the treatment of ovarian cancer, it continues to have an extremely poor prognosis. Heparin-binding epidermal growth factor-like grown factor (HB-EGF) has been reported to be a rational therapeutic target for ovarian cancer. Here, we evaluated the clinical significance of serum HB-EGF by examining the association between prognosis and serum HB-EGF levels in patients with primary ovarian cancer. We found that high serum HB-EGF concentrations were significantly associated with poor prognosis in a combined cohort of patients with all stages of ovarian cancer, as well as in a subset of patients with advanced disease. In addition, serum HB-EGF levels increased as the cancer advanced. These data suggest that serum HB-EGF may be a target for the design of novel therapies for ovarian cancer.

A Modified Adenovirus Vector-Mediated Antibody Screening Method Identifies EphA2 as a Cancer Target.

BACKGROUND: We constructed a genetically modified adenovirus vector incorporating an IgG Fc-binding motif from staphylococcal protein A, Z33 (Adv-FZ33). Adv-FZ33 allows an antibody to redirect the vector to a target molecule on the cell surface. We attempted to search for target antigen candidates and antibodies that allowed highly selective gene transduction into malignant tumors. METHODS: Hybridoma libraries producing monoclonal antibodies (mAbs) were screened that increased transduction efficiency in cancer cell lines after cross-linking with Adv-FZ33. Target antigens of the mAbs were identified by immunoprecipitation and mass spectrometry. Of these mAbs, we noted a clone, F2-27, that recognized the receptor tyrosine kinase EphA2. Next, we generated an adenovirus vector, Ax3CMTK-FZ33, that expressed a herpes simplex virus thymidine kinase (HSV-TK). The therapeutic efficacy of F2-27-mediated HSV-TK gene transduction, followed by ganciclovir (GCV) administration, was studied in vitro. The inhibitory effect of F2-27 on cancer cell invasion was investigated by a three-dimensional spheroid formation assay. RESULTS: In vitro reporter gene expression after Adv-FZ33 infection via F2-27 was 146 times higher than with control mAb in EphA2-expressing cancer cell lines. F2-27-mediated Ax3CMTK-FZ33 infection induced the HSV-TK gene in an F2-27-dependent manner and had a highly effective cytotoxic effect in a GCV-dependent manner. Additionally, F2-27 independently inhibited migration of EphA2-positive breast cancer cell lines in three-dimensional culture. CONCLUSION: Our modified adenovirus and hybridoma screening system is useful for the development of targeted cancer therapy, and F2-27 has the potential to be an antibody-based therapy for various EphA2-positive cancers.

BK-UM in patients with recurrent ovarian cancer or peritoneal cancer: a first-in-human phase-I study.

BACKGROUND: BK-UM (CRM197) is a mutant form of diphtheria toxin and a specific inhibitor of heparin-binding epidermal growth factor-like growth factor (HB-EGF). We assessed the safety, pharmacokinetics, recommended dose, and efficacy of BK-UM in patients with recurrent ovarian cancer (OC) or peritoneal cancer (PC), and measured HB-EGF levels in serum and abdominal fluid after BK-UM administration. METHODS: Eleven patients with advanced or recurrent OC or PC were enrolled and treated with BK-UM via the intraperitoneal route. The dose was escalated (1.0, 2.0, 3.3, and 5.0 mg/m2) using a 3 + 3 design. RESULTS: Eight of 11 patients completed treatment. No dose-limiting toxicity (DLT) was experienced at dose levels 1 (1.0 mg/m2) and 2 (2.0 mg/m2). Grade 3 transient hypotension as an adverse event (defined as a DLT in the present study) was observed in two of four patients at dose level 3 (3.3 mg/m2). Treatment with BK-UM was associated with decreases in HB-EGF levels in serum and abdominal fluid in seven of 11 patients and five of eight patients, respectively. Clinical outcomes included a partial response in one patient, stable disease in five patients, and progressive disease in five patients. CONCLUSIONS: BK-UM was well tolerated at doses of 1.0 and 2.0 mg/m2, with evidence for clinical efficacy in patients with recurrent OC or PC. A dose of 2.0 mg/m2 BK-UM is recommended for subsequent clinical trials. TRIAL REGISTRATION: This trial was prospectively performed as an investigator-initiated clinical trial. The trial numbers are UMIN000001002 and UMIN000001001, with registration dates of 1/30/2008 and 2/4/2008, respectively. UMIN000001001 was registered as a trial for the continuous administration of BK-UM after UMIN000001002 .

Anti-tumor Effect of Intravenous Administration of CRM197 for Triple-negative Breast Cancer Therapy.

BACKGROUND/AIM: Heparin-binding epidermal growth factor-like growth factor (HB-EGF), which belongs to the epidermal growth factor family, is a rational therapeutic target for triple-negative breast cancer (TNBC). This study aimed to assess the anti-tumor efficacy of intravenous (i.v.) HB-EGF-specific inhibitor (CRM197) for TNBC. MATERIALS AND METHODS: NOD/SCID mice were subcutaneously injected withTNBC cells, MDA-MB-231, and, then, treated with i.v. CRM197 in either dose- or frequency-dependent manners, using an advanced cancer model and an adjuvant therapy model. Tumor volume and mouse body weight were calculated weekly. Statistical significance was assessed by the Mann-Whitney U-test. RESULTS: Mice that received i.v. CRM197 showed a significant anti-tumor effect in dose- and frequency-dependent manners in both models. However, their body weight did not differ significantly among groups. CONCLUSION: These results suggest that i.v. CRM197 is an effective treatment for TNBC.

Validity of HB-EGF as Target for Human Neuroblastoma Therapy.

BACKGROUND/AIM: Neuroblastoma (NB) is the most common and lethal extracranial solid tumor in children. The present study aimed to verify that the heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a rational target in NB therapy. MATERIAL AND METHODS: We examined expression of EGFR ligands in four NB cell lines using 2-dimensional culture (DC) and 3DC conditions. To assess the anti-tumor effect of cross-reacting material 197 (CRM197), which is a specific inhibitor of HB-EGF, on NB cells, we also performed terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay to detect apoptotic cells. RESULTS: HB-EGF was predominantly expressed in two out of four NB cell lines under 2DC and 3DC conditions. CRM197 significantly induced apoptosis of NB cells with high HB-EGF expression. CONCLUSION: HB-EGF plays an important role in neuroblastoma tumorigenesis and CRM197 showed an effective antitumor effect in neuroblastoma cells.

Warburg effect regulated by amphiregulin in the development of colorectal cancer.

Colorectal cancer (CRC) is one of the most frequently occurring cancers with high morbidity and mortality worldwide. Amphiregulin (AREG), a member of the epidermal growth factor family and a rational target for CRC therapy, is essential for the three-dimensional structure of tumor formation. To clone the genes associated with increased AREG expression, we performed a cDNA microarray analysis in two CRC cell lines undergoing two-dimensional (2DC) and three-dimensional culture (3DC). Upregulated (>2.0-fold) and downregulated (<0.5-fold) genes in 3DC compared with 2DC were selected. Pathway analysis using DAVID based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway databases revealed a number of genes involved in glycolysis. In CRC cells, glucose elevated the expression of GLUT1 and AREG as well as the activity of the hypoxia-inducible factor 1 (HIF-1) luciferase reporter promoter. The suppression of AREG expression reduced the uptake of glucose and production of lactate. Luciferase assay identified a critical regulatory region for AREG expression between -130 and -180 bp upstream of the start site, which contained a carbohydrate response element (ChoRE). Max-like protein X (MLX) bound to ChoRE and enhanced the expression of AREG. Together these data suggest that AREG plays a pivotal role in the development of CRC through activation of the Warburg effect.

Corrigendum to "Molecular Characterization of a Fully Human Chimeric T-Cell Antigen Receptor for Tumor-Associated Antigen EpCAM".

[This corrects the article DOI: 10.1155/2012/853879.].

Simultaneous genotyping of single-nucleotide polymorphisms in alcoholism-related genes using duplex and triplex allele-specific PCR with two-step thermal cycles.

We developed a time- and cost-effective multiplex allele-specific polymerase chain reaction (AS-PCR) method based on the two-step PCR thermal cycles for genotyping single-nucleotide polymorphisms in three alcoholism-related genes: alcohol dehydrogenase 1B, aldehyde dehydrogenase 2 and µ-opioid receptor. Applying MightyAmp(®) DNA polymerase with optimized AS-primers and PCR conditions enabled us to achieve effective and selective amplification of the target alleles from alkaline lysates of a human hair root, and simultaneously to determine the genotypes within less than 1.5 h using minimal lab equipment.

Optimal production of a fusion protein consisting of a single-chain variable fragment antibody against a tumor-associated antigen and interleukin-2 in fed-batch culture of Pichia pastoris.

BACKGROUND/AIM: The aim of the present study was to establish the strategy for producing a single-chain variable fragment (scFv) antibody fused with interleulin-2 (IL2) by Pichia pastoris and to optimize production during fed-batch cultivation in a 5-l fermenter. MATERIALS AND METHODS: We constructed a fusion sequence consisting of an scFv gene derived from a mouse monoclonal antibody against a tumor-associated antigen (designated MK-1 antigen) and human interleulin-2 (IL-2) gene, ligated the sequences to expression vector pPICZα-A and separately transformed the constructs into Pichia pastoris strains GS115 and KM71H. RESULTS: The highest concentration of secreted fusion protein, 738 ± 44 mg/l, was obtained after a 60-h induction. To investigate the specific binding activity of the partially purified fusion protein, we used an enzyme-linked immunosorbent assay and antigen from a whole-cell lysate. Student's t-test showed that the specific binding activity of the partially-purified fusion protein to the lysate of Chinese hamster ovary cell lines expressing the MK-1 antigen was significantly higher than that of the lysate of CHO cell lines that do not express MK-1. CONCLUSIONS: The method described here permits the production of substantial amounts of the fusion protein for conducting functional studies on the biological role of these fusion proteins.

High expression of fusion proteins consisting of a single-chain variable fragment antibody against a tumor-associated antigen and interleukin-2 in Escherichia coli.

BACKGROUND/AIM: The aim of this study was to establish a strategy for high-level production of single-chain variable fragment (scFv) antibodies fused with interleukin-2 (IL-2) in Escherichia coli. MATERIALS AND METHODS: We constructed two fusion sequences consisting of a scFv gene derived from a mouse monoclonal antibody against a tumor-associated antigen (MK-1) and human Interleukin-2(IL-2) gene, ligated the fusions into pET15b and transformed into three different E. coli strains. The effects of temperature, isopropyl-ß-D-thiogalactopyranoside (IPTG) concentration and duration of IPTG induction were investigated. RESULTS: Employing E. coli strain Rosetta-gami B, which has an oxidizing cytoplasm that facilitates cytoplasmic disulfide bond formation, improved the level of soluble protein expression. Under optimal conditions, the highest levels of fusion protein expression and high percentages of the proteins were found in their soluble form. Specifically, 89.29% (0.28 g/l) of one fusion protein was soluble after a 10-h induction and 84.61% (0.26 g/l) of the other fusion protein was soluble after a separate 10-h induction. When analyzed by enzyme-linked immunosorbent assay, the partially-purified fusion proteins retained a specific binding activity to the cell lysate of Chinese hamster ovary (CHO) cells expressing MK-1. CONCLUSION: Taken together, the methods described herein permit the production of substantial amounts of the fusion proteins for conducting functional studies on the biological role of these fusion proteins.

Novel treatment strategies for cancer and their tumor-targeting approaches using antibodies against tumor-associated antigens.

Novel treatment strategies for cancer that are based on a more detailed understanding over the tumor biology are based on the latest new technology and are expected to improve the current treatment outcome for patients with cancer. However, many of these strategies still have one common and critical problem, being their limited specificity for tumor cells. In this context, antibodies against tumor-associated antigens (TAAs) are used in several ways to increase the tumor specificity of these novel strategies. Firstly, photodynamic or sonodynamic therapy using anti-TAA antibodies conjugated with new sensitizers offers additional therapeutic approaches. Secondly, re-targeting of T-cell immunotherapy using an anti-TAA antibody fusion protein was shown to be useful for the success of cancer immunotherapy, because the down-regulation of HLA class I molecules in tumor tissues constitutes a major tumor escape mechanism associated with tumor-specific cellular immunity. Thirdly, in oncolytic virotherapy, targeting viral vectors carrying cytolytic activity against tumor tissues by modifying the tropisms with anti-TAA antibodies is also very promising from a practical point of view.

Pre-clinical study of BK-UM, a novel inhibitor of HB-EGF, for ovarian cancer therapy.

BACKGROUND/AIM: Heparin-binding epidermal growth factor-like growth factor (HB-EGF), a member of the epidermal growth factor family, is a target for ovarian cancer therapy. The present study investigated the administration schedule of BK-UM, an anticancer agent targeting HB-EGF. MATERIALS AND METHODS: The ovarian cancer cell line, RMG-I, was injected subcutaneously into five-week-old female nude mice. The BK-UM was administered intraperitoneally, using three administration schedules with different doses. The tumor volume was calculated every week. Statistical significance was assessed using the Mann-Whitney U-test. RESULTS: At doses >0.1 mg/kg, BK-UM displayed significant antitumor effects, although the antitumor effects and body weights of mice did not significantly differ by dose or by three different administration schedules. At a dose <0.1 mg/kg, however, BK-UM had little inhibitory effect on tumor growth. CONCLUSION: Daily administration of BK-UM, which has a potentially dose-dependent antitumor effect, may be the optimal schedule for clinical application.

Contribution of transcription factor, SP1, to the promotion of HB-EGF expression in defense mechanism against the treatment of irinotecan in ovarian clear cell carcinoma.

Ovarian clear cell carcinoma (OCCC) is a worst histological subtype than other ovarian malignant tumor. Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a promising target for ovarian cancer therapy. The aims of this study were to validate the efficacy of HB-EGF-targeted therapy for OCCC and to identify the transcription factor that contributed to the induction of HB-EGF by SN38 treatment in OCCC cells. HB-EGF was highly expressed in OCCC cells, and an increase of HB-EGF was induced by SN38 which had only antitumor effect among conventional anticancer agents on OCCC. A specific inhibitor of HB-EGF, a cross-reacting material 197 (CRM197), led to a synergistic increase in the number of apoptotic OCCC cells with the treatment of SN38. The luciferase assay with 5'-deletion promoter constructs identified a GC-rich element between -125 and -178 (the distal transcription start site was denoted +1) as a cis-regulatory region, and the treatment of SN38 induced luciferase activity in this region. An in silico and chromatin immunoprecipitation analysis estimated that SP1 bound to the cis-regulatory region of HB-EGF in OCCC cells. Real-time PCR and cell viability assays showed that the transfection of a small interfering RNA targeting SP1 suppressed the expression of HB-EGF induced by SN38, resulting in the enhanced sensitivity of SN38. Taken together, these results indicate that induction of HB-EGF expression contributed to defense mechanism against treatment of SN38 through the transcriptional activity of SP1 in OCCC cells.

Potent and specific antitumor effect of CEA-targeted photoimmunotherapy.

Conventional photodynamic therapy (PDT) for cancer is limited by the insufficient efficacy and specificity of photosensitizers. We herein describe a highly effective and selective tumor-targeted PDT using a near-infrared (NIR) photosensitizer, IRDye700DX, conjugated to a human monoclonal antibody (Ab) specific for carcinoembryonic antigen (CEA). The antitumor effects of this Ab-assisted PDT, called photoimmunotherapy (PIT), were investigated in vitro and in vivo. The Ab-IRDye conjugate induced potent cytotoxicity against CEA-positive tumor cells after NIR-irradiation, whereas CEA-negative cells were not affected at all, even in the presence of excess photoimmunoconjugate. We found an equivalent phototoxicity and a predominant plasma membrane localization of Ab-IRDye after both one and six hours of incubation. Either no or little caspase activation and membrane peroxidation were observed in PIT-treated cells and a panel of scavengers for reactive oxygen species showed only partial inhibition of the phototoxic effect. Strikingly, Ab-IRDye retained significant phototoxicity even under hypoxia. We established a xenograft model, which allowed us to sensitively investigate the therapeutic efficacy of PIT by non-invasive bioluminescence imaging. Luciferase-expressing MKN-45-luc human gastric carcinoma cells were subcutaneously implanted into both flanks of nude mice. NIR-irradiation was performed for only the tumor on one side. In vivo imaging and measurement of the tumor size revealed that a single PIT treatment, with intraperitoneal administration of Ab-IRDye and subsequent NIR-irradiation, caused rapid cell death and significant inhibition of tumor growth, but only on the irradiated side. Together, these data suggest that Ab-IRDye-mediated PIT has great potential as an anticancer therapeutics targeting CEA-positive tumors.

Fractionated radioimmunotherapy with 9°Y-labeled fully human anti-CEA antibody.

Carcinoembryonic antigen (CEA) is an attractive target molecule of radioimmunotherapy (RIT). To enhance RIT's therapeutic efficacy, the fractionation of radiolabeled antibody doses is an attractive strategy. In this study, a fully human anti-CEA monoclonal antibody (mAb) C2-45 was selected by virtue of its lack of immunogenicity, and the effectiveness of fractionated RIT with yttrium-90 (9°Y)-labeled mAb C2-45 was evaluated. In LS180 tumor-bearing mice, indium-111 (¹¹¹In)-labeled mAb C2-45 showed high and persistent tumor accumulation. Therapeutic studies were performed with single doses of 9°Y-mAb C2-45 (100 or 200 µCi) or double doses of 100 µCi 9°Y-mAb C2-45 at different intervals (5, 10, and 15 days). All 9°Y-mAb C2-45-treated mice showed inhibition of tumor progression, while the time to tumor progression was much longer in both the 200-µCi-treated group and the double 100-µCi-treated group than in the single 100-µCi-treated group. The therapeutic effect of the double 100 µCi administration at days 0 and 15 lasted significantly longer than that in the other treatment groups. These findings indicate that 9°Y-mAb C2-45 may be a promising agent for the treatment of CEA-positive cancer and that the fractionation of 9°Y-labeled antibody doses could enhance the therapeutic effect if performed according to an appropriate protocol.

Therapeutic approaches to the regulation of metabolism of high-density lipoprotein. Novel HDL-directed pharmacological intervention and exercise.

High-density lipoprotein (HDL) and low-density lipoprotein (LDL) particles transport cholesterol in plasma and play an important role in cellular cholesterol homeostasis, which influences cell function. The risk of coronary artery disease (CAD) associated with high levels of LDL-cholesterol (LDL-C) can be reduced by treatment with statins, which reduce LDL-C levels by inhibiting cellular cholesterol synthesis. However, patients who are treated with high doses of statins, especially secondary CAD prevention, regardless of their resulting LDL-C levels, are still at high risk of CAD. Therefore, there has been growing interest in HDL-directed therapies. Inhibitors of cholesteryl ester transfer protein (CETP) substantially increase HDL-C levels (by 31-138%). However, it is still unclear whether or not CETP inhibitors can reduce the risk of CAD associated with low HDL-C levels, while reconstituted HDL or apolipoprotein A-I mimetic peptides increase the functionality of HDL. Low levels of HDL-C are often complicated with metabolic disorders, including hypertriglyceridemia, metabolic syndrome, and type 2 diabetes mellitus, and lifestyle changes are effective for correcting these conditions. Physical activity and exercise training increase HDL-C levels, especially HDL2-C levels, by multiple mechanisms. Therefore, although using HDL-directed therapies that increase HDL-C levels and/or improve the function of HDL is a reasonable approach for reducing the residual risk of CAD as a complement to LDL-C-lowering therapy, lifestyle modifications including exercise to improve metabolic disorders should be considered as the first option.