Haem oxygenase 1 expression is associated with prognosis in cholangiocarcinoma patients and with drug sensitivity in xenografted mice

Iron cycle disruption by heme oxygenase-1 activation leads to a reduced breast cancer cell survival

Heme oxygenase-1 (HO-1), which catalyzes heme degradation releasing iron, regulates several processes related to breast cancer. Iron metabolism deregulation is also connected with several tumor processes. However the regulatory relationship between HO-1 and iron proteins in breast cancer remains unclear. Using human breast cancer biopsies, we found that high HO-1 levels significantly correlated with low DMT1 levels. Contrariwise, high HO-1 levels significantly correlated with high ZIP14 and prohepcidin expression, as well as hemosiderin storage. At mRNA level, we found that high HO-1 expression significantly correlated with low DMT1 expression but high ZIP14, L-ferritin and hepcidin expression. In in vivo experiments in mice with genetic overexpression or pharmacological activation of HO-1, we detected the same expression pattern observed in human biopsies. In in vitro experiments, HO-1 activation induced changes in iron proteins expression leading to an increase of hemosiderin, ROS levels, lipid peroxidation and a decrease of the growth rate. Such low growth rate induced by HO-1 activation was reversed when iron levels or ROS levels were reduced. Our findings demonstrate an important role of HO-1 on iron homeostasis in breast cancer. The changes in iron proteins expression when HO-1 is modulated led to the iron accumulation deregulating the iron cell cycle, and consequently, generating oxidative stress and low viability, all contributing to impair breast cancer progression.

Predictive and prognostic effect of HO-1 expression in breast cancer patients undergoing neoadjuvant chemotherapy

PURPOSE

Heme oxygenase-1 (HO-1) has complex biological function, and is a candidate oncogene with a wide variety of deleterious functions in breast cancer. Here, we evaluated the relationship between expression of HO-1 protein with clinical response to neoadjuvant chemotherapy (NAC) in breast cancer patients.

METHODS

We used immunohistochemistry (IHC) to determine expression of HO-1 protein from core needle biopsy before NAC, then applied univariate and multivariate analyses to understand the relationship between HO-1 with pathological complete response (pCR) outcomes. Next, Kaplan-Meier and Log-rank tests were used to compare disease-free survival (DFS) and overall survival (OS), between groups, and Cox proportional hazards regression analysis applied for prognostic evaluation.

RESULTS

A total of 575 patients with locally advanced invasive breast cancer were included in the study, of which 111 (19.3%) achieved pCR after NAC. Results from multivariate analysis showed that high HO-1 expression was an independent predictor of low pCR rate (OR 0.254, 95% CI 0.026-0.643, p = 0.002). Moreover, results from survival analysis showed that high HO-1 expression was significantly associated with shorter DFS (HR 4.843, 95% CI 1.205-32.572, p = 0.026), but not with OS (HR 3.219, 95% CI 0.928-32.124, p = 0.071). Furthermore, HO-1 expression was significantly associated with lower pCR rate (OR 0.102, 95% CI 0.013-0.352), p = 0.001), poor DFS (HR 8.562, 95% CI 1.592-34.950, p = 0.009), and OS (HR 7.835, 95% CI 1.220-56.213, p = 0.023) of patients with triple-negative breast cancer (TNBC) patients.

CONCLUSION

Our results indicated that HO-1 expression is not only a biomarker for predicting pCR, but also a prognostic factor in breast cancer patients in a neoadjuvant setting, especially in TNBC subgroups.

Clinical Significance of Heme Oxygenase 1 in Tumor Progression

Heme oxygenase 1 (HO-1) plays a key role in cell adaptation to stressors through the antioxidant, antiapoptotic, and anti-inflammatory properties of its metabolic products. For these reasons, in cancer cells, HO-1 can favor aggressiveness and resistance to therapies, leading to poor prognosis/outcome. Genetic polymorphisms of HO-1 promoter have been associated with an increased risk of cancer progression and a high degree of therapy failure. Moreover, evidence from cancer biopsies highlights the possible correlation between HO-1 expression, pathological features, and clinical outcome. Indeed, high levels of HO-1 in tumor specimens often correlate with reduced survival rates. Furthermore, HO-1 modulation has been proposed in order to improve the efficacy of antitumor therapies. However, contrasting evidence on the role of HO-1 in tumor biology has been reported. This review focuses on the role of HO-1 as a promising biomarker of cancer progression; understanding the correlation between HO-1 and clinical data might guide the therapeutic choice and improve the outcome of patients in terms of prognosis and life quality.

Nuclear Localization of Heme Oxygenase-1 in Pathophysiological Conditions: Does It Explain the Dual Role in Cancer?

Heme Oxygenase-1 (HO-1) is a type II detoxifying enzyme that catalyzes the rate-limiting step in heme degradation leading to the formation of equimolar quantities of carbon monoxide (CO), free iron and biliverdin. HO-1 was originally shown to localize at the smooth endoplasmic reticulum membrane (sER), although increasing evidence demonstrates that the protein translocates to other subcellular compartments including the nucleus. The nuclear translocation occurs after proteolytic cleavage by proteases including signal peptide peptidase and some cysteine proteases. In addition, nuclear translocation has been demonstrated to be involved in several cellular processes leading to cancer progression, including induction of resistance to therapy and enhanced metastatic activity. In this review, we focus on nuclear HO-1 implication in pathophysiological conditions with special emphasis on malignant processes. We provide a brief background on the current understanding of the mechanisms underlying how HO-1 leaves the sER membrane and migrates to the nucleus, the circumstances under which it does so and, maybe the most important and unknown aspect, what the function of HO-1 in the nucleus is.

Enhancement of piperlongumine chemosensitivity by silencing heme oxygenase-1 expression in cholangiocarcinoma cell lines

Piperlongumine (PL) produces reactive oxygen species (ROS) and induces G2/M-phase arrest in cholangiocarcinoma (CCA) cells via the JNK/ERK pathway. A differential response to PL was observed among all CCA cell lines However, the underlying mechanisms have remained to be fully elucidated. The aim of the present study was to investigate the molecular mechanisms of PL-induced heme oxygenase-1 (HO-1) expression in CCA cell lines. The anti-proliferative action of PL in the CCA cell lines KKU-100 and KKU-213A was analyzed using sulforhodamine B assays. Reverse transcription-quantitative PCR and western blot analyses were used to examine mRNA and protein expression. HO-1 inhibition was achieved using the chemical inhibitor zinc protophoryn or specific small interfering RNA to HO-1. Intracellular ROS was detected using a 2,7-dichlorodihydrofluorescein diacetate fluorescence assay. High expression of phase-II detoxification enzymes, including NADPH quinone oxidoreductase-1, heme oxygenase-1, superoxide dismutases and aldo-keto reductase 1 subunits C-1 and 3, were detected in the KKU-100 cell line. Of the CCA cell lines tested, KKU-100 was the least sensitive to PL. Dose-dependent upregulation of HO-1 expression via PI3K/Akt activation was detected in PL-treated CCA cells. Inhibition of HO-1 eliminated the antioxidant defense mechanisms, leading to increased anti-cancer activity of PL in the CCA cell lines via an increase in intracellular ROS levels and apoptotic protein expression. These observations indicated that HO-1 inhibition had a chemosensitizing effect on CCA to PL.

Keap1 deletion accelerates mutant K-ras/p53-driven cholangiocarcinoma

The activation of the Kelch-like ECH-associated protein 1 (Keap1)-NF-E2-related factor 2 (Nrf2) pathway contributes to cancer progression in addition to oxidative stress responses. Loss-of-function Keap1 mutations were reported to activate Nrf2, leading to cancer progression. We examined the effects of Keap1 deletion in a cholangiocarcinoma mouse model using a mutant K-ras/p53 mouse. Introduction of the Keap1 deletion into liver-specific mutant K-ras/p53 expression resulted in the formation of invasive cholangiocarcinoma. Comprehensive analyses of the gene expression profiles identified broad upregulation of Nrf2-target genes such as Nqo1 and Gstm1 in the Keap1-deleted mutant K-ras/p53 expressing livers, accompanied by upregulation of cholangiocyte-related genes. Among these genes, the transcriptional factor Sox9 was highly expressed in the dysplastic bile duct. The Keap-Nrf2-Sox9 axis might serve as a novel therapeutic target for cholangiocarcinoma.NEW & NOTEWORTHY The Keap1-Nrf2 system has a wide variety of effects in addition to the oxidative stress response in cancer cells. Addition of the liver-specific Keap1 deletion to mice harboring mutant K-ras and p53 accelerated cholangiocarcinoma formation, together with the hallmarks of Nrf2 activation. This process involved the expansion of Sox9-positive cells, indicating increased differentiation toward the cholangiocyte phenotype.

HO-1 drives autophagy as a mechanism of resistance against HER2-targeted therapies

PURPOSE

Targeted therapies have resulted in major advances in the treatment of HER2-positive breast cancers. Despite this, up to 70% of patients will develop resistance to treatment within 2 years and new strategies for targeting resistant disease are needed.

METHODS

To identify potential resistance mechanisms, we used the mouse MMTV-NIC-PTEN+/- spontaneous model of HER2-positive breast cancer and the pan-HER family kinase inhibitor sapatinib. Vehicle and sapatinib-treated tumors were evaluated by immunohistochemistry and proteomic analysis. In vitro studies were carried out to define the role of heme oxygenase 1 (HO-1) and autophagy in resistance to sapatinib and lapatinib, another pan-HER family kinase inhibitor.

RESULTS

Treatment of tumor-bearing MMTV-NIC-PTEN+/- mice with sapatinib resulted in delayed tumor progression and increased survival. However, tumors eventually progressed on treatment. Proteomic analysis identified proteins associated with cellular iron homeostasis as being upregulated in the sapatinib-treated tumors. This included HO-1 whose overexpression was confirmed by immunohistochemistry. Overexpression of HO-1 in HER2-expressing SKBR3 breast cancer cells resulted in reduced sensitivity to both pan-HER family kinase inhibitors sapatinib and lapatinib. This was associated with increased autophagy in the HO-1 over-expressing cells. Furthermore, increased autophagy was also seen in the sapatinib-treated tumors. Treatment with autophagy inhibitors was able to increase the sensitivity of the HO-1 over-expressing cells to both lapatinib and sapatinib.

CONCLUSION

Together these data indicate a role for HO-1-induced autophagy in resistance to pan-HER family kinase inhibitors.

Piperlongumine induces autophagy in biliary cancer cells via reactive oxygen species-activated Erk signaling pathway

Biliary cancer (BC) is an aggressive neoplasm with high mortality. BC can be categorized into three groups: Intrahepatic cholangiocarcinoma (CCA; also known as bile duct cancer), extrahepatic cholangiocarcinoma and gallbladder cancer. Due to its heterogeneity and aggressiveness, the response to current chemotherapy and radiotherapy methods in patients with BC is poor. Therefore, there is an urgent requirement to develop drugs to treat BC. Piperlongumine (PL), a naturally occurring small molecule isolated from Piper longum L., exhibits anticancer activity by inducing reactive oxygen species (ROS) production. In the present study, the effects of PL on cell proliferation, cell cycle, apoptosis and autophagy in BC cells were investigated. PL induced BC cell death in a concentration‑ and time‑dependent manner by inducing ROS production. PL induced cell cycle arrest in CCA cells (HuCCT‑1) and gallbladder cancer cells (OCUG‑1) cells, but with distinct cell cycle distribution profiles. PL caused G2/M cell cycle arrest in HuCCT‑1 cells, and G0/G1 cell cycle arrest in OCUG‑1 cells. PL induced apoptosis and autophagy; PL treatment induced accumulation of LC3‑II in a concentration‑ and time‑dependent manner. The Erk signaling pathway appeared to be involved in autophagy induction. Application of the ROS scavenger, N‑acetyl‑l‑cysteine, to BC cells attenuated the cell death, cell cycle arrest, apoptosis and autophagy induced by PL treatment. These findings indicated that PL may be a potential agent for BC treatment in the future.

Heme Oxygenase-1 Has an Antitumor Role in Breast Cancer

Aims: Heme oxygenase-1 (HO-1) is an enzyme involved in cellular responses to oxidative stress and has also been shown to regulate processes related to cancer progression. In this regard, HO-1 has been shown to display a dual effect with either antitumor or protumor activity, which is also true for breast cancer (BC). In this work, we address this discrepancy regarding the role of HO-1 in BC. Results: HO-1 was detected in human BC tissues, and its protein levels correlated with reduced tumor size and longer overall survival time of patients, thus suggesting the clinical importance of HO-1 in this type of cancer. Contrariwise, nuclear localization of HO-1 correlated with higher tumor grade suggesting that the effect of HO-1 is dependent on its cellular localization. In vivo experiments showed that both pharmacological activation and genetic overexpression of HO-1 reduce the tumor burden in two different animal models of BC. Furthermore, the pharmacological and genetic activation of HO-1 in several BC cell lines reduce the cellular viability by inducing apoptosis and cell cycle arrest and decrease the cellular migration and invasion rates by modulating pathways involved in the epithelial-mesenchymal transition. Furthermore, HO-1 activation impaired in vivo the metastatic dissemination. Innovation and Conclusion: By using various BC cell lines and animal models as well as human tumor samples, we demonstrated that total HO-1 displays antitumor activities in BC. Furthermore, our study suggests that HO-1 subcellular localization may explain the differential effects observed for the protein in different tumor types.

Metformin sensitizes cholangiocarcinoma cell to cisplatin-induced cytotoxicity through oxidative stress mediated mitochondrial pathway

AIMS

Metformin (Met), an essential antidiabetic agent, shows antitumor activity in some cancers. A previous study showed that Met enhanced cytotoxic activity of cisplatin (Cis) in cholangiocarcinoma (CCA) in association with the activation of AMP-activated protein kinase and suppression of Akt-mTOR. However, these effects do not entirely explain the observed chemosensitizing effect. The present study investigated the interaction of Met and Cis over the enhanced antitumor effect.

MAIN METHODS

KKU-100 and KKU-M156 cells were used in the study. Cytotoxicity was assessed by acridine orange-ethidium bromide staining. Reactive oxygen species (ROS) and mitochondrial transmembrane potential (Δψm) were measured by dihydroethidium and JC-1 fluorescent methods. Cellular glutathione (GSH) and redox ratio were analyzed by enzymatic coupling assay. Proteins associated with antioxidant system and cell death were evaluated by western immunoblot.

KEY FINDINGS

Cytotoxicity of Cis was enhanced by Met in association with ROS formation and GSH redox stress. The antioxidants, N-acetylcysteine and TEMPOL, and MPTP inhibitor, cyclosporine, attenuated cytotoxicity in association with suppression of ROS formation and the losses of Δψm. Met in combination with Cis suppressed expression of Nrf2 and altered the expression of Bcl2 family proteins.

SIGNIFICANCE

The chemosensitizing effect of Met in combination with Cis is causally associated with increased oxidative stress-mediated mitochondrial cell death pathway. Met may improve the efficacy of Cis in the treatment of cancer.

Heme Oxygenase-1 Inhibitors Induce Cell Cycle Arrest and Suppress Tumor Growth in Thyroid Cancer Cells

Heme oxygenase-1 (HO-1) is induced by a variety of stimuli and plays a multifaceted role in cellular protection. We have shown that HO-1 is overexpressed in thyroid cancer and is associated with tumor aggressiveness. Therefore, we set out to assess the effects of HO-1 inhibitors on the biology of thyroid cancer cells. Two different classes of HO-1 inhibitors were used, including a metalloporphyrin, zinc protoporphyrin-IX (ZnPP), and an azole antifungal agent, ketoconazole. The viability and colony formation of thyroid cancer cells decreased in a concentration- and time-dependent fashion following treatment with HO-1 inhibitors. Cancer cells exhibited a higher sensitivity to HO-1 inhibitors than non-malignant cells. HO-1 inhibitors induced a G0/G1 arrest accompanied by decreased cyclin D1 and CDK4 expressions and an increase in levels of p21 and p27. HO-1 inhibitors significantly increased intracellular ROS levels and suppressed cell migration and invasion. Oxygen consumption rate and mitochondrial mass were increased with ZnPP treatment. Mice treated with ZnPP had a reduced xenograft growth and diminished cyclin D1 and Ki-67 staining in tumor sections. Taken together, HO-1 inhibitors might have therapeutic potential for inducing cell cycle arrest and promoting growth suppression of thyroid cancer cells in vitro and in vivo.

Metformin enhances cisplatin induced inhibition of cholangiocarcinoma cells via AMPK-mTOR pathway

AIMS

AMP-activated protein kinase (AMPK) functions as a cellular energy sensor regulating various aspects of cellular metabolism. Metformin (Met), an activator of AMPK, has been reported to reduce the cancer risk and enhance antitumor effects in certain cancers. Cholangiocarcinoma (CCA) is an aggressive malignancy which rarely responds to chemotherapeutic agents. We investigated the chemosensitizing effects of Met in CCA cells.

MATERIALS AND METHODS

KKU-100 and KKU-452 cells were used in the study. Antiproliferation of Met and cisplatin (Cis) was analyzed by sulforhodamine B and colony forming assays. Apoptotic cell death was analyzed by acridine orange and ethidium bromide staining method. Cell cycle analysis was performed by flow cytometric method. Effects on cell migration and invasion were analyzed by wound healing assay and transwell chamber method. Expression of proteins was examined by western blot analysis.

KEY FINDINGS

Met enhanced the antiproliferation of Cis, and conferred antimigration and anti-invasion in CCA cells, where Cis alone did not have two latter effects. This chemosensitizing effect is related to the activation of AMPK and suppression of Akt, mTOR and p70S6K. Met and Cis increased expression of p53 and p21 and suppressed expression of cyclin D1. This effect was associated with cell cycle arrest at S phase. The anti-invasion effect was casually associated with the suppression of FAK expression. The cytotoxic effect of the drug combination was mimicked by AICAR, an AMPK agonist.

SIGNIFICANCE

Met may be a novel agent to increase the efficacy of Cis to treat CCA.

Piperlongumine induces G2/M phase arrest and apoptosis in cholangiocarcinoma cells through the ROS-JNK-ERK signaling pathway

Cholangiocarcinoma (CCA) is an aggressive, metastatic bile duct cancer. CCA is difficult to diagnose, and responds poorly to current radio- and chemo-therapy. Piperlongumine (PL) is a naturally-occurring small molecule selectively toxic to cancer cells by targeting reactive oxygen species (ROS). In this study, we demonstrated the potential anticancer activity of PL in CCA. PL markedly induced death in CCA cell lines in a dose- and time-dependent manner through the activation of caspase-3 and PARP. PL also stimulated ROS accumulation in CCA. Co-exposure of PL with the ROS scavenger N-acetyl-L-cysteine or GSH completely blocked PL-induced apoptosis in CCA cell lines. Increased p21 via the p53-independent pathway in PL-treated CCA cells led to G2/M phase arrest and cell apoptosis. In addition, the study showed that PL trigger CCA cell lines death through JNK-ERK activation. Furthermore, the different antioxidant capacity of CCA cell lines also indicates the susceptibility of the cells to PL treatment. Our findings reveal that PL exhibits anti-tumor activity and has potential to be used as a chemotherapeutic agent against CCA.

Establishment of cholangiocarcinoma cell lines from patients in the endemic area of liver fluke infection in Thailand

Cholangiocarcinoma is a rare type of cancer which is an increasingly discernible health threat. The disease is usually very difficult in diagnosis and various treatment modalities are typically not effective. Cholangiocarcinoma is a complex and very heterogeneous malignancy characterized by tumor location, different risk factors, molecular profiling, and prognosis. Cancer cell lines represent an important tool for investigation in various aspects of tumor biology and molecular therapeutics. We established two cell lines, KKU-452 and KKU-023, which were derived from patients residing in the endemic area of liver fluke infection in Thailand. Both of tumor tissues have gross pathology of perihilar and intrahepatic mass-forming cholangiocarcinoma. Two cell lines were characterized for their biological, molecular and genetic properties. KKU-452 and KKU-023 cells are both adherent cells with epithelium morphology, but have some differences in their growth pattern (a doubling time of 17.9 vs 34.8 h, respectively) and the expression of epithelial bile duct markers, CK7 and CK19. Cytogenetic analysis of KKU-452 and KKU-023 cells revealed their highly complex karyotypes; hypertriploid and hypotetraploid, respectively, with multiple chromosomal aberrations. Both cell lines showed mutations in p53 but not in KRAS. KKU-452 showed a very rapid migration and invasion properties in concert with low expression of E-cadherin and high expression of N-cadherin, whereas KKU-023 showed opposite characters. KKU-023, but not KKU-452, showed in vivo tumorigenicity in xenografted nude mice. Those two established cholangiocarcinoma cell lines with unique characters may be valuable for better understanding the process of carcinogenesis and developing new therapeutics for the patients.

Protective effect of CDDO-ethyl amide against high-glucose-induced oxidative injury via the Nrf2/HO-1 pathway

BACKGROUND CONTEXT

Intervertebral disc degeneration (IDD) is the main cause of low back pain, and nucleus pulposus (NP) cell apoptosis is an important risk factor of IDD. However, the molecular mechanism of this disease remains unknown.

PURPOSE

To assess the potential protective effect of CDDO-ethyl amide (EA) against high-glucose-induced oxidative stress injury in NP cells and to investigate the mechanism of antioxidative effects and apoptotic inhibition.

STUDY DESIGN/SETTING

To find new molecule to inhibit intervertebral disc degeneration.

METHODS

Viability, reactive oxygen species (ROS) levels, and apoptosis were examined in NP cells. The protein expression levels of HO-1 and Nrf2 were measured through Western blot RESULTS: CDDO-EA elicited cytoprotective effects against NP cell apoptosis and ROS accumulation induced by high glucose. CDDO-EA treatment increased the HO-1 and Nrf2 expression abrogated by HO-1, Nrf2, and mitogen-activated protein kinase inhibitors.

CONCLUSIONS

The phosphorylation and nuclear translocation of Nrf2 are crucial for HO-1 overexpression induced by CDDO-EA, which is essential for the cytoprotection against high-glucose-induced oxidative stress in NP cells.

HO-1 Induction in Cancer Progression: A Matter of Cell Adaptation

The upregulation of heme oxygenase-1 (HO-1) is one of the most important mechanisms of cell adaptation to stress. Indeed, the redox sensitive transcription factor Nrf2 is the pivotal regulator of HO-1 induction. Through the antioxidant, antiapoptotic, and antinflammatory properties of its metabolic products, HO-1 plays a key role in healthy cells in maintaining redox homeostasis and in preventing carcinogenesis. Nevertheless, several lines of evidence have highlighted the role of HO-1 in cancer progression and its expression correlates with tumor growth, aggressiveness, metastatic and angiogenetic potential, resistance to therapy, tumor escape, and poor prognosis, even though a tumor- and tissue-specific activity has been observed. In this review, we summarize the current literature regarding the pro-tumorigenic role of HO-1 dependent tumor progression as a promising target in anticancer strategy.

LncRNAs H19 and HULC, activated by oxidative stress, promote cell migration and invasion in cholangiocarcinoma through a ceRNA manner

Background

Long non-coding RNAs (lncRNAs) are known to play important roles in different cell contexts, including cancers. However, little is known about lncRNAs in cholangiocarcinoma (CCA), a cholangiocyte malignancy with poor prognosis, associated with chronic inflammation and damage to the biliary epithelium. The aim of the study is to identify if any lncRNA might associate with inflammation or oxidative stress in CCA and regulate the disease progression.

Methods

In this study, RNA-seqs datasets were used to identify aberrantly expressed lncRNAs. Small interfering RNA and overexpressed plasmids were used to modulate the expression of lncRNAs, and luciferase target assay RNA immunoprecipitation (RIP) was performed to explore the mechanism of miRNA-lncRNA sponging.

Results

We firstly analyzed five available RNA-seqs datasets to investigate aberrantly expressed lncRNAs which might associate with inflammation or oxidative stress. We identified that two lncRNAs, H19 and HULC, were differentially expressed among all the samples under the treatment of hypoxic or inflammatory factors, and they were shown to be stimulated by short-term oxidative stress responses to H₂O₂ and glucose oxidase in CCA cell lines. Further studies revealed that these two lncRNAs promoted cholangiocyte migration and invasion via the inflammation pathway. H19 and HULC functioned as competing endogenous RNAs (ceRNAs) by sponging let-7a/let-7b and miR-372/miR-373, respectively, which activate pivotal inflammation cytokine IL-6 and chemokine receptor CXCR4.

Conclusions

Our study revealed that H19 and HULC, up-regulated by oxidative stress, regulate CCA cell migration and invasion by targeting IL-6 and CXCR4 via ceRNA patterns of sponging let-7a/let-7b and miR-372/miR-373, respectively. The results suggest that these lncRNAs might be the chief culprits of CCA pathogenesis and progression. The study provides new insight into the mechanism linking lncRNA function with CCA and may serve as novel targets for the development of new countermeasures of CCA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-016-0348-0) contains supplementary material, which is available to authorized users.