Quantitative imaging for development of companion diagnostics to drugs targeting HGF/MET

Targeting MET amplification in Gastro-oesophageal (GO) malignancies and overcoming MET inhibitor resistance: challenges and opportunities

INTRODUCTION

MET, the hepatocyte growth factor receptor is amplified in 8% of gastroesophageal (GO) malignancies and associated with poor prognosis. Therapeutic targeting of MET amplification and MET mutations has the potential to improve outcomes for patients with GO cancers (GOC).

AREAS COVERED

The efficacy of MET inhibition (METi) in preclinical studies has yet to translate into meaningful improvements in the treatment paradigm for unselected GOC. MET amplification has been proposed as a superior modality for patient selection; however even if confirmed, frequency and duration of response to METi are limited by rapid activation of primary and secondary resistance pathways. These observations illustrate the challenges inherent in the application of precision oncology predicated on the theory of oncogenic addiction.

EXPERT OPINION

A standardized definition of MET positivity is critical to enhance patient selection. Early successes targeting the METex14 skipping mutation demonstrate the potent therapeutic effects of METi in a clearly molecularly defined cohort. There is robust preclinical rationale and early-phase data supporting exploitation of immune system interaction with MET. Pragmatic investigation of rational therapeutic combinations based on molecular profiling of both primary and metastatic disease sites with sequential circulating tumor DNA analysis can inform successful clinical development of METi agents in GOC.

The Occurrence of MET Ectodomain Shedding in Oral Cancer and Its Potential Impact on the Use of Targeted Therapies

Simple Summary

Head and neck cancer is the sixth most common cancer type worldwide, comprising tumors of the upper aero/digestive tract. Approximately 50% of these cancers originate in the oral cavity. Depending on disease stage, oral cancer patients are treated with single-modality surgery, or in combination with radiotherapy with or without chemotherapy. Despite advances in these modalities, the 5-year survival rate is merely 50%. Therefore, implementation of targeted therapies, directed against signaling molecules, has gained attention. One potential target is the MET protein, which can be present on the surface of cancer cells, orchestrating aggressive behavior. As cancer cells can shed the extracellular part of MET from their surface, it is important to identify for MET positive patients whether they possess the entire and/or only the intracellular part of the receptor to assess whether targeted therapies directed against the extracellular, intracellular, or both parts of MET need to be implemented.

Abstract

The receptor tyrosine kinase MET has gained attention as a therapeutic target. Although MET immunoreactivity is associated with progressive disease, use of targeted therapies has not yet led to major survival benefits. A possible explanation is the lack of companion diagnostics (CDx) that account for proteolytic processing. During presenilin-regulated intramembrane proteolysis, MET’s ectodomain is shed into the extracellular space, which is followed by γ-secretase-mediated cleavage of the residual membranous C-terminal fragment. The resulting intracellular fragment is degraded by the proteasome, leading to downregulation of MET signaling. Conversely, a membrane-bound MET fragment lacking the ectodomain (MET-EC^-) can confer malignant potential. Use of C- and N-terminal MET monoclonal antibodies (moAbs) has illustrated that MET-EC^- occurs in transmembranous C-terminal MET-positive oral squamous cell carcinoma (OSCC). Here, we propose that ectodomain shedding, resulting from G-protein-coupled receptor transactivation of epidermal growth factor receptor signaling, and/or overexpression of ADAM10/17 and/or MET, stabilizes and possibly activates MET-EC^- in OSCC. As MET-EC^- is associated with poor prognosis in OSCC, it potentially has impact on the use of targeted therapies. Therefore, MET-EC^- should be incorporated in the design of CDx to improve patient stratification and ultimately prolong survival. Hence, MET-EC^- requires further investigation seen its oncogenic and predictive properties.

Mesenchymal Epithelial Transition Factor (MET): A Key Player in Chemotherapy Resistance and an Emerging Target for Potentiating Cancer Immunotherapy

The MET protein is a cell surface receptor tyrosine kinase predominately expressed in epithelial cells. Upon binding of its only known ligand, hepatocyte growth factor (HGF), MET homodimerizes, phosphorylates, and stimulates intracellular signalling to drive cell proliferation. Amplification or hyperactivation of MET is frequently observed in various cancer types and it is associated with poor response to conventional and targeted chemotherapy. More recently, emerging evidence also suggests that MET/HGF signalling may play an immunosuppressive role and it could confer resistance to cancer immunotherapy. In this review, we summarized the preclinical and clinical evidence of MET's role in drug resistance to conventional chemotherapy, targeted therapy, and immunotherapy. Previous clinical trials investigating MET-targeted therapy in unselected or MET-overexpressing cancers yielded mostly unfavourable results. More recent clinical studies focusing on MET exon 14 alterations and MET amplification have produced encouraging treatment responses to MET inhibitor therapy. The translational relevance of MET inhibitor therapy to overcome drug resistance in cancer patients is discussed.

Mutant POLQ and POLZ/REV3L DNA polymerases may contribute to the favorable survival of patients with tumors with POLE mutations outside the exonuclease domain

BACKGROUND

Mutations in the exonuclease domain of POLE, a DNA polymerase associated with DNA replication and repair, lead to cancers with ultra-high mutation rates. Most studies focus on intestinal and uterine cancers with POLE mutations. These cancers exhibit a significant immune cell infiltrate and favorable prognosis. We questioned whether loss of function of other DNA polymerases can cooperate to POLE to generate the ultramutator phenotype.

METHODS

We used cases and data from 15 cancer types in The Cancer Genome Atlas to investigate mutation frequencies of 14 different DNA polymerases. We tested whether tumor mutation burden, patient outcome (disease-free survival) and immune cell infiltration measured by ESTIMATE can be attributed to mutations in POLQ and POLZ/REV3L.

RESULTS

Thirty six percent of colorectal, stomach and endometrial cancers with POLE mutations carried additional mutations in POLQ (E/Q), POLZ/REV3L (E/Z) or both DNA polymerases (E/Z/Q). The mutation burden in these tumors was significantly greater compared to POLE-only (E) mutant tumors (p < 0.001). In addition, E/Q, E/Z, and E/Q/Z mutant tumors possessed an increased frequency of mutations in the POLE exonuclease domain (p = 0.013). Colorectal, stomach and endometrial E/Q, E/Z, and E/Q/Z mutant tumors within TCGA demonstrated 100% disease-free survival, even if the POLE mutations occurred outside the exonuclease domain (p = 0.003). However, immune scores in these tumors were related to microsatellite instability (MSI) and not POLE mutation status. This suggests that the host immune response may not be the sole mechanism for prolonged disease-free survival of ultramutated tumors in this cohort.

CONCLUSION

Results in this study demonstrate that mutations in POLQ and REV3L in POLE mutant tumors should undergo further investigation to determine whether POLQ and REV3L mutations contribute to the ultramutator phenotype and favorable outcome of patients with POLE mutant tumors.

A novel immunohistochemical scoring system reveals associations of C-terminal MET, ectodomain shedding, and loss of E-cadherin with poor prognosis in oral squamous cell carcinoma

Using tissue microarrays, it was shown that membranous C-terminal MET immunoreactivity and ectodomain (ECD) shedding are associated with poor prognosis in oral cancer. Seen the potential diagnostic value, extrapolation of these results to whole-tissue sections was investigated. Because MET orchestrates epithelial-to-mesenchymal transition (EMT), the results were benchmarked to loss of E-cadherin, a readout for EMT known to be associated with poor prognosis. C-terminal MET, N-terminal MET, and E-cadherin immunoreactivities were examined on formalin-fixed paraffin-embedded parallel sections of 203 oral cancers using antibody clones D1C2, A2H2-3, and NCH-38. Interantibody and intra-antibody relations were examined using a novel scoring system, nonparametric distribution, and median tests. Survival analyses were used to examine the prognostic value of the observed immunoreactivities. Assessment of the three clones revealed MET protein status (no, decoy, transmembranous C-terminal positive), ECD shedding, and EMT. For C-terminal MET-positive cancers, D1C2 immunoreactivity is independently associated with poor overall survival (hazard ratio [HR] = 2.40; 95% confidence interval [CI] = 1.25 to 4.61; and P = 0.008) and disease-free survival (HR = 1.83; 95% CI = 1.07-3.14; P = 0.027). For both survival measures, this is also the case for ECD shedding (43.4%, with HR = 2.30; 95% CI = 1.38 to 3.83; and P = 0.001 versus HR = 1.87; 95% CI = 1.19-2.92; P = 0.006) and loss of E-cadherin (55.3%, with HR = 2.21; 95% CI = 1.30 to 3.77; and P = 0.004 versus HR = 1.90; 95% CI = 1.20-3.01; P = 0.007). The developed scoring system accounts for MET protein status, ECD shedding, and EMT and is prognostically informative. These findings may contribute to development of companion diagnostics for MET-based targeted therapy.

MET ectodomain shedding is associated with poor disease-free survival of patients diagnosed with oral squamous cell carcinoma

Ectodomain shedding unleashes the aggressive nature of the MET oncogene product. Using specific C- and N-terminal MET antibodies (D1C2 and A2H2-3), MET protein status (i.e., no MET, decoy MET, transmembranous C-terminal MET with or without the ectodomain) was investigated in oral squamous cell carcinoma. For the cancers showing transmembranous C-terminal MET, the impact of ectodomain shedding on prognosis was investigated. To examine ectodomain shedding, reduced lysates of oral squamous cell carcinoma cell lines were immunoblotted using D1C2 and an ELISA was performed on culture media using A2H2-3. In addition, reduced lysates of fresh frozen tissues of 30 oral squamous cell carcinoma were immunoblotted using D1C2 and immunohistochemistry was performed on corresponding formalin-fixed paraffin-embedded tissues using both antibodies on parallel sections. To examine MET protein status, differences between membranous D1C2 and A2H2-3 immunoreactivities were scored using parallel tissue microarray sections representing 156 oral squamous cell carcinoma. The prognostic value of ectodomain shedding was examined using Cox regression analysis for disease-free survival and overall survival. Ectodomain shedding was observed in all cell lines, 43% (n = 13) of fresh frozen and 50% (n = 15) of formalin-fixed paraffin-embedded cancers (27% overlap, n = 8). The tissue microarray showed no MET in 23% (n = 36), decoy MET in 9% (n = 14), and transmembranous C-terminal MET in 68% (n = 106) of examined cancers. Within the latter group, ectodomain shedding occurs in 36% (n = 38) of the cases and is independently associated with poor disease-free survival (HR = 2.41; 95% CI, 1.35-4.30 and P = 0.003)-though not overall survival (HR = 1.64; 95% CI, 0.92-2.94 and P = 0.095)-after correcting for factors known to influence survival. In conclusion, MET ectodomain shedding occurs in transmembranous C-terminal MET positive oral squamous cell carcinoma and is independently associated with disease-free survival. These findings might aid in designing companion diagnostics for targeted therapies directed against MET.

MET targeting: time for a rematch

MET, the receptor tyrosine kinase (RTK) for hepatocyte growth factor, is a proto-oncogene involved in embryonic development and throughout life in homeostasis and tissue regeneration. Deregulation of MET signaling has been reported in numerous malignancies, prompting great interest in MET targeting for cancer therapy. The present review offers a summary of the biology of MET and its known functions in normal physiology and carcinogenesis, followed by an overview of the most relevant MET-targeting strategies and corresponding clinical trials, highlighting both past setbacks and promising future prospects. By placing their efforts on a more precise stratification strategy through the genetic analysis of tumors, modern trials such as the NCI-MATCH trial could revive the past enthusiasm for MET-targeted therapy.

The immunophenotype of decidual macrophages in acute atherosis

PROBLEM

Acute atherosis is a uteroplacental arterial lesion that is associated with pregnancy complications such as preeclampsia and preterm birth, the latter being the leading cause of perinatal morbidity and mortality worldwide. However, the immunobiology of acute atherosis is poorly understood.

METHOD OF STUDY

Placental basal plate samples were collected from women who delivered with (n = 11) and without (n = 31) decidua basalis lesions of acute atherosis. Multicolor flow cytometry was used to quantify M1- and M2-like macrophage subsets and the expression of iNOS and IL-12 by decidual macrophages. Multiplex fluorescence staining and phenoptics were performed to localize M1-, MOX-, and Mhem-like macrophages in the decidual basalis.

RESULTS

Macrophages displayed diverse phenotypes in the decidua basalis with acute atherosis. M2-like macrophages were the most abundant subset in the decidua; yet, this macrophage subset did not change with the presence of acute atherosis. Decidual M1-like macrophages were increased in acute atherosis, and such macrophages displayed a pro-inflammatory phenotype, as indicated by the expression of iNOS and IL-12. Decidual M1-like pro-inflammatory macrophages were localized near both transformed and non-transformed vessels in the decidua basalis with acute atherosis. MOX and Mhem macrophages were also identified near transformed vessels in the decidua basalis with acute atherosis. Finally, monocyte-like cells were present on the vessel wall of non-transformed decidual vessels, indicating a possible intravascular source for macrophages in acute atherosis.

CONCLUSION

Decidual macrophages display different phenotypes, namely M1-like, M2-like, MOX, and Mhem subsets. Yet, pro-inflammatory macrophages are enriched in the decidua basalis with acute atherosis. These findings provide a molecular foundation for future mechanistic inquiries about the role of pro-inflammatory macrophages in the pathogenesis of acute atherosis.

Spatial Mapping of Myeloid Cells and Macrophages by Multiplexed Tissue Staining

An array of phenotypically diverse myeloid cells and macrophages (MC&M) resides in the tumor microenvironment, requiring multiplexed detection systems for visualization. Here we report an automated, multiplexed staining approach, named PLEXODY, that consists of five MC&M-related fluorescently-tagged antibodies (anti - CD68, - CD163, - CD206, - CD11b, and - CD11c), and three chromogenic antibodies, reactive with high- and low-molecular weight cytokeratins and CD3, highlighting tumor regions, benign glands and T cells. The staining prototype and image analysis methods which include a pixel/area-based quantification were developed using tissues from inflamed colon and tonsil and revealed a unique tissue-specific composition of 14 MC&M-associated pixel classes. As a proof-of-principle, PLEXODY was applied to three cases of pancreatic, prostate and renal cancers. Across digital images from these cancer types we observed 10 MC&M-associated pixel classes at frequencies greater than 3%. Cases revealed higher frequencies of single positive compared to multi-color pixels and a high abundance of CD68+/CD163+ and CD68+/CD163+/CD206+ pixels. Significantly more CD68+ and CD163+ vs. CD11b+ and CD11c+ pixels were in direct contact with tumor cells and T cells. While the greatest percentage (~70%) of CD68+ and CD163+ pixels was 0–20 microns away from tumor and T cell borders, CD11b+ and CD11c+ pixels were detected up to 240 microns away from tumor/T cell masks. Together, these data demonstrate significant differences in densities and spatial organization of MC&M-associated pixel classes, but surprising similarities between the three cancer types.

Genomic Status of MET Potentiates Sensitivity to MET and MEK Inhibition in NF1-Related Malignant Peripheral Nerve Sheath Tumors

Malignant peripheral nerve sheath tumors (MPNST) are highly resistant sarcomas that occur in up to 13% of individuals with neurofibromatosis type I (NF1). Genomic analysis of longitudinally collected tumor samples in a case of MPNST disease progression revealed early hemizygous microdeletions in NF1 and TP53, with progressive amplifications of MET, HGF, and EGFR To examine the role of MET in MPNST progression, we developed mice with enhanced MET expression and Nf1 ablation (Nf1^fl/ko;lox-stop-loxMET^tg/+;Plp-creERT^tg/+ ; referred to as NF1-MET). NF1-MET mice express a robust MPNST phenotype in the absence of additional mutations. A comparison of NF1-MET MPNSTs with MPNSTs derived from Nf1^ko/+;p53^R172H;Plp-creERT^tg/+ (NF1-P53) and Nf1^ko/+;Plp-creERT^tg/+ (NF1) mice revealed unique Met, Ras, and PI3K signaling patterns. NF1-MET MPNSTs were uniformly sensitive to the highly selective MET inhibitor, capmatinib, whereas a heterogeneous response to MET inhibition was observed in NF1-P53 and NF1 MPNSTs. Combination therapy of capmatinib and the MEK inhibitor trametinib resulted in reduced response variability, enhanced suppression of tumor growth, and suppressed RAS/ERK and PI3K/AKT signaling. These results highlight the influence of concurrent genomic alterations on RAS effector signaling and therapy response to tyrosine kinase inhibitors. Moreover, these findings expand our current understanding of the role of MET signaling in MPNST progression and identify a potential therapeutic niche for NF1-related MPNSTs.Significance: Longitudinal genomic analysis reveals a positive selection for MET and HGF copy number gain early in malignant peripheral nerve sheath tumor progression. Cancer Res; 78(13); 3672-87. ©2018 AACR.

Targeting MET and EGFR crosstalk signaling in triple-negative breast cancers

There is a vital need for improved therapeutic strategies that are effective in both primary and metastatic triple-negative breast cancer (TNBC). Current treatment options for TNBC patients are restricted to chemotherapy; however tyrosine kinases are promising druggable targets due to their high expression in multiple TNBC subtypes. Since coexpression of receptor tyrosine kinases (RTKs) can promote signaling crosstalk and cell survival in the presence of kinase inhibitors, it is likely that multiple RTKs will need to be inhibited to enhance therapeutic benefit and prevent resistance. The MET and EGFR receptors are actionable targets due to their high expression in TNBC; however crosstalk between MET and EGFR has been implicated in therapeutic resistance to single agent use of MET or EGFR inhibitors in several cancer types. Therefore it is likely that dual inhibition of MET and EGFR is required to prevent crosstalk signaling and acquired resistance. In this study, we evaluated the heterogeneity of MET and EGFR expression and activation in primary and metastatic TNBC tumorgrafts and determined the efficacy of MET (MGCD265 or crizotinib) and/or EGFR (erlotinib) inhibition against TNBC progression. Here we demonstrate that combined MET and EGFR inhibition with either MGCD265 and erlotinib treatment or crizotinib and erlotinib treatment were highly effective at abrogating tumor growth and significantly decreased the variability in treatment response compared to monotherapy. These results advance our understanding of the RTK signaling architecture in TNBC and demonstrate that combined MET and EGFR inhibition may be a promising therapeutic strategy for TNBC patients.

Quantitative Analysis of a Multiplexed Immunofluorescence Panel in T-Cell Lymphoma

Immunohistochemistry (IHC) provides clinically useful information on protein expression in cancer cells. However, quantification of colocalizing signals using conventional IHC and visual scores is challenging. Here we describe the application of quantitative immunofluorescence in angioimmunoblastic T-cell lymphoma (AITL), a peripheral T-cell lymphoma characterized by cellular heterogeneity that impedes IHC interpretation and quantification. A multiplexed immunofluorescence (IF) panel comprising T- and B-lymphocyte markers along with T-follicular helper (T_FH) markers was validated for appropriate cellular localization in sections of benign tonsillar tissue and tested in two samples of AITL, using a Vectra microscope for spectral imaging and InForm software for analysis. We measured the percentage positivity of the T_FH markers, BCL6 and PD1, in AITL CD4-positive cells to be approximately 26% and 45%, with 12% coexpressing both markers. The pattern is similar to CD4 cells within the germinal center of normal tonsils and clearly distinct from extragerminal CD4 cells. This study demonstrates the feasibility of automated and quantitative imaging of a multiplexed panel of cellular markers in formalin-fixed, paraffin-embedded tissue sections of a cellularly heterogenous lymphoma. Multiplexed IF allows the simultaneous scoring of markers in malignant and immune cell populations and could potentially increase accuracy for establishment of diagnostic thresholds.

Data integration from pathology slides for quantitative imaging of multiple cell types within the tumor immune cell infiltrate

Background

Immune cell infiltrates (ICI) of tumors are scored by pathologists around tumor glands. To obtain a better understanding of the immune infiltrate, individual immune cell types, their activation states and location relative to tumor cells need to be determined. This process requires precise identification of the tumor area and enumeration of immune cell subtypes separately in the stroma and inside tumor nests. Such measurements can be accomplished by a multiplex format using immunohistochemistry (IHC).

Method

We developed a pipeline that combines immunohistochemistry (IHC) and digital image analysis. One slide was stained with pan-cytokeratin and CD45 and the other slide with CD8, CD4 and CD68. The tumor mask generated through pan-cytokeratin staining was transferred from one slide to the other using affine image co-registration. Bland-Altman plots and Pearson correlation were used to investigate differences between densities and counts of immune cell underneath the transferred versus manually annotated tumor masks. One-way ANOVA was used to compare the mask transfer error for tissues with solid and glandular tumor architecture.

Results

The overlap between manual and transferred tumor masks ranged from 20%–90% across all cases. The error of transferring the mask was 2- to 4-fold greater in tumor regions with glandular compared to solid growth pattern (p < 10⁻⁶). Analyzing data from a single slide, the Pearson correlation coefficients of cell type densities outside and inside tumor regions were highest for CD4 + T-cells (r = 0.8), CD8 + T-cells (r = 0.68) or CD68+ macrophages (r = 0.79). The correlation coefficient for CD45+ T- and B-cells was only 0.45. The transfer of the mask generated an error in the measurement of intra- and extra- tumoral CD68+, CD8+ or CD4+ counts (p < 10⁻¹⁰).

Conclusions

In summary, we developed a general method to integrate data from IHC stained slides into a single dataset. Because of the transfer error between slides, we recommend applying the antibody for demarcation of the tumor on the same slide as the ICI antibodies.

Electronic supplementary material

The online version of this article (10.1186/s13000-017-0658-8) contains supplementary material, which is available to authorized users.

MET4 expression predicts poor prognosis of gastric cancers with Helicobacter pylori infection

The role of HGF/SF‐MET signaling is important in cancer progression, but its relation with Helicobacter pylori‐positive gastric cancers remains to be elucidated. In total, 201 patients with primary gastric carcinoma who underwent curative or debulking resection without preoperative chemotherapy were studied. MET4 and anti‐HGF/SF mAbs were used for immunohistochemical analysis. Survival of gastric cancer patients was estimated by Kaplan–Meier method and compared with log‐rank. Cox proportional hazards models were fit to determine the independent association of MET‐staining status with outcome. The effect of live H. pylori bacteria on cell signaling and biological behaviors was evaluated using gastric cancer cell lines. MET4‐positive gastric cancers showed poorer prognosis than MET4‐negative cases (overall survival, P = 0.02; relapse‐free survival, P = 0.06). Positive staining for MET4 was also a statistically significant factor to predict poor prognosis in H. pylori‐positive cases (overall survival, P < 0.01; relapse‐free survival, P = 0.01) but not in H. pylori‐negative cases. Gastric cancers positively stained with both HGF/SF and MET4 showed a tendency of the worst prognosis. Stimulation of MET‐positive gastric cancer cells with live H. pylori bacteria directly upregulated MET phosphorylation and activated MET downstream signals such as p44/42MAPK and Akt, conferring cell proliferation and anti‐apoptotic activity. In conclusion, positive staining for MET4 was useful for predicting poor prognosis of gastric cancers with H. pylori infection. Helicobacter pylori stimulated MET‐positive gastric cancers and activated downstream signaling, thereby promoting cancer proliferation and anti‐apoptotic activity. These results support the importance of H. pylori elimination from gastric epithelial surface in clinical therapy.