Functional disruption of macrophage migration inhibitory factor (MIF) suppresses proliferation of human H460 lung cancer cells by caspase-dependent apoptosis

The Tautomerase Activity of Tumor Exosomal MIF Promotes Pancreatic Cancer Progression by Modulating MDSC Differentiation

Pancreatic cancer is a deadly disease that is largely resistant to immunotherapy, in part because of the accumulation of immunosuppressive cells in the tumor microenvironment (TME). Much evidence suggests that tumor-derived exosomes (TDE) contribute to the immunosuppressive activity mediated by myeloid-derived suppressor cells (MDSC) within the pancreatic cancer TME. However, the underlying mechanisms remain elusive. Herein, we report that macrophage migration inhibitory factor (MIF) in TDEs has a key role in inducing MDSC formation in pancreatic cancer. We identified MIF in both human and murine pancreatic cancer-derived exosomes. Upon specific shRNA-mediated knockdown of MIF, the ability of pancreatic cancer-derived exosomes to promote MDSC differentiation was abrogated. This phenotype was rescued by reexpression of the wild-type form of MIF rather than a tautomerase-null mutant or a thiol-protein oxidoreductase-null mutant, indicating that both MIF enzyme activity sites play a role in exosome-induced MDSC formation in pancreatic cancer. RNA sequencing data indicated that MIF tautomerase regulated the expression of genes required for MDSC differentiation, recruitment, and activation. We therefore developed a MIF tautomerase inhibitor, IPG1576. The inhibitor effectively inhibited exosome-induced MDSC differentiation in vitro and reduced tumor growth in an orthotopic pancreatic cancer model, which was associated with decreased numbers of MDSCs and increased infiltration of CD8+ T cells in the TME. Collectively, our findings highlight a pivotal role for MIF in exosome-induced MDSC differentiation in pancreatic cancer and underscore the potential of MIF tautomerase inhibitors to reverse the immunosuppressive pancreatic cancer microenvironment, thereby augmenting anticancer immune responses.

Hallmarks of Cancer Affected by the MIF Cytokine Family

New diagnostic methods and treatments have significantly decreased the mortality rates of cancer patients, but further improvements are warranted based on the identification of novel tumor-promoting molecules that can serve as therapeutic targets. The macrophage migration inhibitory factor (MIF) family of cytokines, comprising MIF and DDT (also known as MIF2), are overexpressed in almost all cancer types, and their high expressions are related to a worse prognosis for the patients. MIF is involved in 9 of the 10 hallmarks of cancer, and its inhibition by antibodies, nanobodies, or small synthetic molecules has shown promising results. Even though DDT is also proposed to be involved in several of the hallmarks of cancer, the available information about its pro-tumoral role and mechanism of action is more limited. Here, we provide an overview of the involvement of both MIF and DDT in cancer, and we propose that blocking both cytokines is needed to obtain the maximum anti-tumor response.

Association of Polymorphisms in Inflammation Genes With the Prognosis of Advanced Non-Small Cell Lung Cancer Patients Receiving Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitors

Background

Inflammation is not only involved in the development and progression of cancer but also affects the response to therapy. The aim of this study was to investigate the association of single nucleotide polymorphisms (SNPs) in inflammation genes with the prognosis of advanced non-small cell lung cancer (NSCLC) patients treated with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs).

Methods

Forty-seven SNPs were genotyped in 318 advanced NSCLC patients receiving EGFR-TKIs. Of 318 patients, 182 (57.2%) patients died during follow-up period. We assessed the association of SNPs with the progression-free survival (PFS) and overall survival (OS) as well as calculated the weighted genetic risk score (GRS). We also explored the expression levels and prognostic values of inflammation genes in lung adenocarcinoma (LUAD) in Gene Expression Profiling Interactive Analysis (GEPIA) and using UCSC Xena, respectively. The relationship between the expression levels of IL15, IL17RA, AGER, MIF, and TNFRSF1A and EGFR mutation status was analyzed using UCSC Xena.

Results

In single variant analyses, 3 SNPs (rs10519613, rs4819554, and rs4149570) were significantly associated with worse PFS. Five SNPs (rs10519613, rs4819554, rs2070600, rs755622, and rs4149570) were significantly with worse OS. In addition, high and intermediate GRSs (based on rs10519613, rs4819554, and rs4149570) were associated with worse PFS than those with low GRS. For OS, patients with high GRSs (based on rs10519613, rs4819554, rs2070600, rs755622, and rs4149570) had shorter survival time than those with low GRS. Furthermore, IL15, IL17RA, AGER, MIF, and TNFRSF1A were dysregulated in LUAD. There was difference in the expression level of TNFRSF1A between EGFR wildtype and EGFR-mutant LUAD. Both low AGER expression and high TNFRSF1A expression were significantly associated with worse PFS in LUAD. In addition, low IL17RA and AGER expression, high MIF and TNFRSF1A expression were significantly associated with worse OS in LUAD.

Conclusion

SNPs in inflammation genes could serve as prognostic biomarkers for NSCLC patients treated with EGFR-TKIs.

HDAC/MIF dual inhibitor inhibits NSCLC cell survival and proliferation by blocking the AKT pathway

Non-small-cell lung carcinoma (NSCLC) is one of the most common forms of lung cancer, and a leading cause of cancer death among human beings. There is an urgent demand for novel therapeutics for the treatment of NSCLC to enhance the efficacy of the currently applied Tyrosine kinase inhibitors (TKIs) therapy and to overcome therapy-resistance. Here, we report a novel small-molecule inhibitor that simultaneously targets histone deacetylase (HDAC) and macrophage migration inhibitory factor (MIF). The HDAC/MIF dual inhibitor proved to be toxic for EGFR mutated (H1650, TKI-resistant) or knock out (A549 EGFR^-/-) NSCLC cell lines. Further experiments showed that HDAC inhibition inhibits cell survival and proliferation, while MIF inhibition downregulates pAKT or AKT expression level, which both interfere with cell survival. Furthermore, the combination treatment of TKI and HDAC/MIF dual inhibitor showed that the dual inhibitor enhanced TKI inhibitory efficacy, highlighting the advantages of HDAC/MIF dual inhibitor for more effective treatment of NSCLC.

Spontaneous regression of micro-metastases following primary tumor excision: a critical role for primary tumor secretome

BACKGROUND

Numerous case studies have reported spontaneous regression of recognized metastases following primary tumor excision, but underlying mechanisms are elusive. Here, we present a model of regression and latency of metastases following primary tumor excision and identify potential underlying mechanisms.

RESULTS

Using MDA-MB-231HM human breast cancer cells that express highly sensitive luciferase, we monitored early development stages of spontaneous metastases in BALB/c nu/nu mice. Removal of the primary tumor caused marked regression of micro-metastases, but not of larger metastases, and in vivo supplementation of tumor secretome diminished this regression, suggesting that primary tumor-secreted factors promote early metastatic growth. Correspondingly, MDA-MB-231HM-conditioned medium increased in vitro tumor proliferation and adhesion and reduced apoptosis. To identify specific mediating factors, cytokine array and proteomic analysis of MDA-MB-231HM secretome were conducted. The results identified significant enrichment of angiogenesis, growth factor binding and activity, focal adhesion, and metalloprotease and apoptosis regulation processes. Neutralization of MDA-MB-231HM-secreted key mediators of these processes, IL-8, PDGF-AA, Serpin E1 (PAI-1), and MIF, each antagonized secretome-induced proliferation. Moreover, their in vivo simultaneous blockade in the presence of the primary tumor arrested the development of micro-metastases. Interestingly, in the METABRIC cohort of breast cancer patients, elevated expression of Serpin E1, IL-8, or the four factors combined predicted poor survival.

CONCLUSIONS

These results demonstrate regression and latency of micro-metastases following primary tumor excision and a crucial role for primary tumor secretome in promoting early metastatic growth in MDA-MB-231HM xenografts. If generalized, such findings can suggest novel approaches to control micro-metastases and minimal residual disease.

Inhibition of Macrophage Migration Inhibitory Factor by a Chimera of Two Allosteric Binders

Human Macrophage Migration Inhibitory Factor (MIF) is a trimeric cytokine implicated in a number of inflammatory and autoimmune diseases and cancer. We previously reported that the dye p425 (Chicago Sky Blue), which bound MIF at the interface of two MIF trimers covering the tautomerase and allosteric pockets, revealed a unique strategy to block MIF's pro-inflammatory activities. Structural liabilities, including the large size, precluded p425 as a medicinal chemistry lead for drug development. We report here a rational design strategy linking only the fragment of p425 that binds over the tautomerase pocket to the core of ibudilast, a known MIF allosteric site-specific inhibitor. The chimeric compound, termed L2-4048, was shown by X-ray crystallography to bind at the allosteric and tautomerase sites as anticipated. L2-4048 retained target binding and blocked MIF's tautomerase CD74 receptor binding, and pro-inflammatory activities. Our studies lay the foundation for the design and synthesis of smaller and more drug-like compounds that retain the MIF inhibitory properties of this chimera.

The role of MIF in chronic lung diseases: looking beyond inflammation

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that has been associated with many diseases. Most studies found in literature describe MIF as a proinflammatory cytokine involved in chronic inflammatory conditions, but evidence from last years suggests that many of its key effects are not directly related to inflammation. In fact, MIF is constitutively expressed in most human tissues and in some cases in high levels, which does not reflect the pattern of expression of a classic proinflammatory cytokine. Moreover, MIF is highly expressed during embryonic development and decreases during adulthood, which point toward a more likely role as growth factor. Accordingly, MIF knockout mice develop age-related spontaneous emphysema, suggesting that MIF presence (e.g., in younger individuals and wild-type animals) is part of a healthy lung. In view of this new line of evidence, we aimed to review data on the role of MIF in the pathogenesis of chronic lung diseases.

Knockdown of CD-74 in the Proliferative and Apoptotic Activity of Breast Cancer Cells

BACKGROUND

The cluster of differentiation (CD) 74 is known for its immunological functions and its elevated level was reported in various cancer cells.

AIM

The aim of the present study was to investigate the expression and potential roles of CD74 in the proliferative and apoptotic activity of breast cancer.

METHODS

Expression of CD74, macrophage migration inhibitory factor (MIF) and CD44 was assayed in CAMA-1 and MDA-MB-231 cell lines using flow cytometry. CD74 was knocked down using CD74 siRNA-transfection in CAMA-1, and MDA-MB-231 cells and proliferation and apoptosis were determined in the transfected breast cancer cells.

RESULTS

The data showed that CD74, MIF and CD44 were expressed in breast cancer cell lines and were associated with cell proliferation and apoptosis. Correlation analysis revealed that CD74 was positively correlated and colocalised with MIF on the cell-surface of CAMA-1 and MDA-MB-231. The knockdown of CD74 significantly reduced CAMA-1 and MDA-MB-231 cell proliferation and increased the level of apoptotic cells.

CONCLUSION

We concluded that the interactions of CD74 with MIF and CD74 with CD44 could be a potential tumour marker for breast cancer cells. Moreover, the level of co-expression of MIF and CD74 or CD44 could be a surrogate marker for the efficacy of anti-angiogenic drugs, particularly in breast cancer tumours. In short, the study revealed the potential roles of CD74 in the proliferation and apoptosis of breast cancer which may serve as a potential therapeutic target for breast cancer.

Prognostic role of macrophage migration inhibitory factor expression in patients with squamous cell carcinoma of the lung

Background

Macrophage migration inhibitory factor (MIF) has been shown to play an important role in the inflammatory and immune response in squamous cell carcinoma (SCC). Recent studies have reported that MIF is involved in the tumorigenesis and overexpressed in various cancers. In this study, we assessed the prognostic role of MIF expression in SCC of the lung, and demonstrated the effect of knockdown of MIF on the migration in lung SCC cell lines.

Methods

The relationship between MIF expression and clinicopathological parameters and the prognostic role of MIF expression were evaluated with immunohistochemical staining in 96 patients with SCC of the lung. The expression of MIF mRNA and protein was analyzed by semi‐quantitative polymerase chain reaction and Western blot in lung SCC cell. The effect of knockdown of MIF was assessed by wound healing assay.

Results

The high percentage of MIF‐positive cells was significantly associated with lymph node metastasis (P = 0.004), and was a poor prognostic factor of disease‐free survival (DFS) (hazard ratio [HR]: 3.125; 95% confidence interval [CI], 1.628–5.998; P = 0.001) and disease‐specific survival (DSS) (HR: 2.303; 95% CI, 1.172–4.525; P = 0.016). Moreover, Kaplan‐Meier analysis showed that SCC patients with a high percentage of MIF‐positive cells had a significantly lower DFS (P = 0.001) and DSS (P = 0.014) than those with a low percentage. Furthermore, wound healing assay revealed that knockdown of MIF resulted in decreased cellular migration.

Conclusion

MIF is closely associated with tumor progression and could be a prognostic factor in SCC of the lung.

Macrophage migration inhibitory factor enhances influenza-associated mortality in mice

Influenza-associated mortality continues to occur annually despite available antiviral therapies. New therapies that improve host immunity could reduce influenza virus disease burden. Targeting macrophage migration inhibitory factor (MIF) has improved the outcomes of certain inflammatory diseases, but its role in influenza viral infection is unclear. Here, we showed that, during influenza viral infection, Mif-deficient mice have less inflammation, viral load, and mortality compared with WT control mice; conversely, Tg mice, overexpressing Mif in alveolar epithelial cells, had higher inflammation, viral load, and mortality. Antibody-mediated blockade of MIF in WT mice during influenza viral infection improved their survival. Mif-deficient murine lungs showed reduced levels of parkin, a mitophagy protein that negatively regulates antiviral signaling, prior to infection and augmented antiviral type I/III IFN levels in the airspaces after infection as compared with WT lungs. Additionally, in vitro assays with human lung epithelial cells showed that treatment with recombinant human MIF increased the percentage of influenza virus-infected cells. In conclusion, our study reveals that MIF impairs antiviral host immunity and increases inflammation during influenza infection and suggests that targeting MIF could be therapeutically beneficial during influenza viral infection.

Macrophage Migration Inhibitory Factor protects cancer cells from immunogenic cell death and impairs anti-tumor immune responses

The Macrophage Migration Inhibitory Factor (MIF) is an inflammatory cytokine that is overexpressed in a number of cancer types, with increased MIF expression often correlating with tumor aggressiveness and poor patient outcomes. In this study, we aimed to better understand the link between primary tumor expression of MIF and increased tumor growth. Using the MMTV-PyMT murine model of breast cancer, we observed that elevated MIF expression promoted tumor appearance and growth. Supporting this, we confirmed our previous observation that higher MIF expression supported tumor growth in the 4T1 murine model of breast cancer. We subsequently discovered that loss of MIF expression in 4T1 cells led to decreased cell numbers and increased apoptosis in vitro under reduced serum culture conditions. We hypothesized that this increase in cell death would promote detection by the host immune system in vivo, which could explain the observed impairment in tumor growth. Supporting this, we demonstrated that loss of MIF expression in the primary tumor led to an increased abundance of intra-tumoral IFNgamma-producing CD4+ and CD8+ T cells, and that depletion of T cells from mice bearing MIF-deficient tumors restored growth to the level of MIF-expressing tumors. Furthermore, we found that MIF depletion from the tumor cells resulted in greater numbers of activated intra-tumoral dendritic cells (DCs). Lastly, we demonstrated that loss of MIF expression led to a robust induction of a specialized form of cell death, immunogenic cell death (ICD), in vitro. Together, our data suggests a model in which MIF expression in the primary tumor dampens the anti-tumor immune response, promoting tumor growth.

Role of macrophage migration inhibitory factor in mesenchymal epithelial transition of cervical carcinoma cells

Cervical cancer is a kind of female malignant tumor with increasing incidence recently. Macrophage migration inhibitory factor (MIF) is a major tumor facilitating factor. The previous study suggests that there was a correlation between MIF and migration or invasion of tumors. Epithelial mesenchymal transition (EMT) is the basis for tumor invasion and migration. Therefore, this study utilized MFI to treat cervical carcinoma Hela cells, and the mechanism of EMT was also further analyzed. Cervical carcinoma Hela cells were transfected with pFenesil MIF siRNA plasmids, following by real-time fluorescent quantitative PCR to detect MIF levels. MTT assay was then utilized for evaluate the proliferative activity of Hela cells after transfection. The cell invasion and migration were examined. The expression of E-cadherin and Vimentin were also detected. The results indicated that the MIF was positively expressed in Hela cells, whose MIF mRNA level was increased after the transfection (P<0.05). Compared to the control or blank group, the transfected group had elevated proliferative activity with elongated incubation time (P<0.05). Both invasion and migration functions of transfected cells were significantly potentiated (P<0.05) compared to the control or blank group. E-cadherin expression level was also decreased in experimental group. MIF was also expressed in cervical carcinoma Hela cells. Elevated MIF level could facilitate the cell invasion and migration, and elevate the Vimentin and decrease E-cadherin expression, thus facilitating EMT.

MiR-451 suppresses proliferation, migration and promotes apoptosis of the human osteosarcoma by targeting macrophage migration inhibitory factor

Previous studies have shown that MiR-451 plays an important role in human osteosarcoma carcinogenesis, but the underlying mechanism by which MiR-451 affects the osteosarcoma has not been fully understood. This study intends to uncover the mechanism by which MiR-451 functions as a tumor suppressor. The expression of MiR-451 in osteosarcoma tissues and osteosarcoma cell lines was monitored by real-time PCR. The proliferation ability was examined by MTT and cell cycle assay. The migration and apoptosis of cells were monitored by migration assay and flow cytometry, respectively. Moreover, the angiogenesis of HUVEC cells transfected with MiR-451 mimics was examined by tube formation assay. The effect of MiR-451 on MIF was determined by luciferase assays and Western blot assay. The results showed that MiR-451 expression level was significantly reduced in the osteosarcoma compared with normal bone tissues. Overexpression of MiR-451 significantly attenuated the proliferation and migration, and induced the apoptosis of osteosarcoma cells. Furthermore, the angiogenesis of HUVEC cells transfected with MiR-451 mimics was assayed and the decreased angiogenic ability was detected compared to the controls. Finally, we demonstrated that MiR-451 overexpression inhibited the malignant behavior of osteosarcoma by downregulating MIF. These findings suggest that MiR-451 may act as a tumor suppressor in osteosarcoma. MiR-451 inhibited cell proliferation, migration and angiogenesis and promoted apoptosis of human osteosarcoma cells, at least partially, by inhibiting the expression of MIF. MiR-451/MIF may be a novel therapeutic target in treatment of osteosarcoma.

Down-regulated SOX4 expression suppresses cell proliferation, metastasis and induces apoptosis in Xuanwei female lung cancer patients

The transcription factor SOX4 has functional importance in foetal lung maturation and tumorigenesis in a number of cancers. However, its biological functions in the progression of lung tumorigenesis remain unclear. In this study, we found that the expression levels of SOX4 mRNA and protein were significantly higher in Xuanwei female lung cancer tissues than in benign lung lesions. The patients with high expression of the SOX4 protein had a higher pathological grade, lymph node (LN) metastasis, poor tumor differentiation and worse prognosis than those patients with low expression of SOX4. Knockdown of the SOX4 gene in the Xuanwei female lung cancer cell line XWLC-05 resulted in apoptotic morphological changes, decreased cell proliferation, invasion and migration. Furthermore, knockdown of the SOX4 gene resulted in obvious sub-G1 peaks and induction of apoptosis through upregulation of caspase-3 expression, while in cells treated with a caspase-3 inhibitor, apoptosis induced by silencing SOX4 expression was inhibited. In vivo analysis in nude mice further confirmed that knockdown of SOX4 suppressed tumor growth. In conclusion, SOX4 appears to be an important tumor suppressor gene in the regulation of Xuanwei female lung cancer cell proliferation, apoptosis and metastases, and it may be a potential target for effective lung cancer therapy.

MicroRNA‑451 inhibits neuroblastoma proliferation, invasion and migration by targeting macrophage migration inhibitory factor

Neuroblastoma (NB) is the most prevalent type of extracranial solid tumour in young children. To improve current understanding of the mechanisms, which modulate cancer cell proliferation, invasion and migration, investigations have focused on microRNAs (miRs), a class of small non‑coding RNAs, which post‑transcriptionally regulate gene expression during various crucial cell processes. The present study aimed to investigate the role of miR‑451 in NB. Human NB tissue and adjacent normal tissue were surgically removed, and the expression of miR‑451, and development and pathological characteristics of NB were investigated. The expression of miR‑451 was reduced in the NB tissue, compared with that in the adjacent tissue, and correlations between the reduction in miR‑451 and unfavourable variables included tumour size (P=0.0081), differentiation (P=0.0217), lymph node metastasis (P=0.0489), tumour‑node‑metastasis stage (0.0220) and distant metastases (P=0.0201). Transfection of the SK‑N‑SH and GI‑LA‑N NB cell lines with miR‑451 inhibited cell growth, invasion and migration. Furthermore, the present study demonstrated that macrophage migration inhibitory factor (MIF) was regulated directly by miR‑451 and was a critical mediator of the biological effects of miR‑451 in NB. The re‑expression of MIF markedly reversed the carcinogenic inhibitory property of miR‑451. These data provide a more detailed understanding of the essential role of miR‑451 in NB, which relies on regulation of the expression of MIF.

In silico target fishing and pharmacological profiling for the isoquinoline alkaloids of Macleaya cordata (Bo Luo Hui)

Background

Some isoquinoline alkaloids from Macleaya cordata (Willd). R. Br. (Bo Luo Hui) exhibited antibacterial, antiparasitic, antitumor, and analgesic effects. The targets of these isoquinoline alkaloids are undefined. This study aims to investigate the compound–target interaction network and potential pharmacological actions of isoquinoline alkaloids of M. cordata by reverse pharmacophore database screening.

Methods

The targets of 26 isoquinoline alkaloids identified from M. cordata were predicted by a pharmacophore-based target fishing approach. Discovery Studio 3.5 and two pharmacophore databases (PharmaDB and HypoDB) were employed for the target profiling. A compound–target interaction network of M. cordata was constructed and analyzed by Cytoscape 3.0.

Results

Thirteen of the 65 predicted targets identified by PharmaDB were confirmed as targets by HypoDB screening. The targets in the interaction network of M. cordata were involved in cancer (31 targets), microorganisms (12 targets), neurodegeneration (10 targets), inflammation and autoimmunity (8 targets), parasitosis (5 targets), injury (4 targets), and pain (3 targets). Dihydrochelerythrine (C6) was found to hit 23 fitting targets. Macrophage migration inhibitory factor (MIF) hits 15 alkaloids (C1–2, C11–16, C19–25) was the most promising target related to cancer.

Conclusion

Through in silico target fishing, the anticancer, anti-inflammatory, and analgesic effects of M. cordata were the most significant among many possible activities. The possible anticancer effects were mainly contributed by the isoquinoline alkaloids as active components.

Macrophage migration inhibitory factor engages PI3K/Akt signalling and is a prognostic factor in metastatic melanoma

Background

Macrophage migration inhibitory factor (MIF) is a widely expressed cytokine involved in a variety of cellular processes including cell cycle regulation and the control of proliferation. Overexpression of MIF has been reported in a number of cancer types and it has previously been shown that MIF is upregulated in melanocytic tumours with the highest expression levels occurring in malignant melanoma. However, the clinical significance of high MIF expression in melanoma has not been reported.

Methods

MIF expression was depleted in human melanoma cell lines using siRNA-mediated gene knockdown and effects monitored using in vitro assays of proliferation, cell cycle, apoptosis, clonogenicity and Akt signalling. In silico analyses of expression microarray data were used to correlate MIF expression levels in melanoma tumours with overall patient survival using a univariate Cox regression model.

Results

Knockdown of MIF significantly decreased proliferation, increased apoptosis and decreased anchorage-independent growth. Effects were associated with reduced numbers of cells entering S phase concomitant with decreased cyclin D1 and CDK4 expression, increased p27 expression and decreased Akt phosphorylation. Analysis of clinical outcome data showed that MIF expression levels in primary melanoma were not associated with outcome (HR = 1.091, p = 0.892) whereas higher levels of MIF in metastatic lesions were significantly associated with faster disease progression (HR = 2.946, p = 0.003 and HR = 4.600, p = 0.004, respectively in two independent studies).

Conclusions

Our in vitro analyses show that MIF functions upstream of the PI3K/Akt pathway in human melanoma cell lines. Moreover, depletion of MIF inhibited melanoma proliferation, viability and clonogenic capacity. Clinically, high MIF levels in metastatic melanoma were found to be associated with faster disease recurrence. These findings support the clinical significance of MIF signalling in melanoma and provide a strong rationale for both targeting and monitoring MIF expression in clinical melanoma.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-630) contains supplementary material, which is available to authorized users.