Parametric mapping of immunohistochemically stained tissue sections; a method to quantify the colocalization of tumor markers

MHC-I and PD-L1 Expression is Associated with Decreased Tumor Outgrowth and is Radiotherapy-inducible in the Murine Head and Neck Squamous Cell Carcinoma Model MOC1

INTRODUCTION

Combined radiotherapy and immune checkpoint inhibition is a potential treatment option for head and neck squamous cell carcinoma (HNSCC). Immunocompetent mouse models can help to successfully develop radio- immunotherapy combinations and to increase our understanding of the effects of radiotherapy on the tumor microenvironment for future clinical translation. Therefore, the aim of this study was to develop a homogeneous, reproducible HNSCC model originating from the Mouse Oral Cancer 1 (MOC1) HNSCC cell line, and to explore the radiotherapy-induced changes in its tumor microenvironment, using flow cytometry and PD-L1 microSPECT/CT imaging.

MATERIALS AND METHODS

In vivo growing tumors originating from the parental MOC1 line were used to generate single cell derived clones. These clones were screened in vitro for their ability to induce programmed cell death ligand 1 (PD-L1) and major histocompatibility complex class I (MHC-I) following IFNγ exposure. Clones with different IFNγ sensitivity were inoculated in C57BL/6 mice and assessed for tumor outgrowth. The composition of the tumor microenvironment of a stably growing (non)irradiated MOC1-derived clone was assessed by immunohistochemistry, flow cytometry and PD-L1 microSPECT/CT.

RESULTS

Low in vitro inducibility of MHC-I and PD-L1 by IFNγ was associated with increased tumor outgrowth of MOC1 clones in vivo. Flow cytometry analysis of cells derived from a stable in vivo growing MOC1 clone MOC1.3D5low showed expression of MHC-I and PD-L1 on several cell populations within the tumor. Upon irradiation, MHC-I and PD-L1 increased on leukocytes (CD45.2+) and cancer associated fibroblasts (CD45.2-/EpCAM-/CD90.1+). Furthermore, PD-L1 microSPECT/CT showed increased tumor uptake of radiolabeled PD-L1 antibodies with a heterogeneous spatial distribution of the radio signal, which co-localized with PD-L1+ and CD45.2+ areas.

DISCUSSION

PD-L1 and MHC-I inducibility by IFNγ in vitro is associated with tumor outgrowth of MOC1 clones in vivo. In tumors originating from a stably growing MOC1-derived clone, expression of these immune-related markers was induced by irradiation shown by flow cytometry on several cell populations within the tumor microenvironment such as immune cells and cancer associated fibroblasts. PD-L1 microSPECT/CT showed increased tumor uptake following radiotherapy, and autoradiography showed correlation of uptake with areas that are heavily infiltrated by immune cells. Knowledge of radiotherapy-induced effects on the tumor microenvironment in this model can help optimize timing and dosage for radio- immunotherapy combination strategies in future research.

Design of ion channel blocking, toxin-like Kunitz inhibitor peptides from the tapeworm, Echinococcus granulosus, with potential anti-cancer activity

Over-expression of K+ channels has been reported in human cancers and is associated with the poor prognosis of several malignancies. EAG1, a particular potassium ion channel, is widely expressed in the brain but poorly expressed in other normal tissues. Kunitz proteins are dominant in metazoan including the dog tapeworm, Echinococcus granulosus. Using computational analyses on one A-type potassium channel, EAG1, and in vitro cellular methods, including major cancer cell biomarkers expression, immunocytochemistry and whole-cell patch clamp, we demonstrated the anti-tumor activity of three synthetic small peptides derived from E. granulosus Kunitz4 protease inhibitors. Experiments showed induced significant apoptosis and inhibition of proliferation in both cancer cell lines via disruption in cell-cycle transition from the G0/G1 to S phase. Western blotting showed that the levels of cell cycle-related proteins including P27 and P53 were altered upon kunitz4-a and kunitz4-c treatment. Patch clamp analysis demonstrated a significant increase in spontaneous firing frequency in Purkinje neurons, and exposure to kunitz4-c was associated with an increase in the number of rebound action potentials after hyperpolarized current. This noteworthy component in nature could act as an ion channel blocker and is a potential candidate for cancer chemotherapy based on potassium channel blockage.

Quantitative Imaging of Hypoxic CAIX-Positive Tumor Areas with Low Immune Cell Infiltration in Syngeneic Mouse Tumor Models

Limited diffusion of oxygen in combination with increased oxygen consumption leads to chronic hypoxia in most solid malignancies. This scarcity of oxygen is known to induce radioresistance and leads to an immunosuppressive microenvironment. Carbonic anhydrase IX (CAIX) is an enzyme functioning as a catalyzer for acid export in hypoxic cells and is an endogenous biomarker for chronic hypoxia. The aim of this study is to develop a radiolabeled antibody that recognizes murine CAIX to visualize chronic hypoxia in syngeneic tumor models and to study the immune cell population in these hypoxic areas. An anti-mCAIX antibody (MSC3) was conjugated to diethylenetriaminepentaacetic acid (DTPA) and radiolabeled with indium-111 (¹¹¹In). CAIX expression on murine tumor cells was determined using flow cytometry, and in vitro affinity of [¹¹¹In]In-MSC3 was analyzed in a competitive binding assay. Ex vivo biodistribution studies were performed to determine in vivo radiotracer distribution. CAIX⁺ tumor fractions were determined by mCAIX microSPECT/CT, and the tumor microenvironment was analyzed using immunohistochemistry and autoradiography. We showed that [¹¹¹In]In-MSC3 binds to CAIX-expressing (CAIX⁺) murine cells in vitro and accumulates in CAIX⁺ areas in vivo. We optimized the use of [¹¹¹In]In-MSC3 for preclinical imaging such that it can be applied in syngeneic mouse models and showed that we can quantitatively distinguish between tumor models with varying CAIX⁺ fractions by ex vivo analyses and in vivo mCAIX microSPECT/CT. Analysis of the tumor microenvironment identified these CAIX⁺ areas as less infiltrated by immune cells. Together these data demonstrate that mCAIX microSPECT/CT is a sensitive technique to visualize hypoxic CAIX⁺ tumor areas that exhibit reduced infiltration of immune cells in syngeneic mouse models. In the future, this technique may enable visualization of CAIX expression before or during hypoxia-targeted or hypoxia-reducing treatments. Thereby, it will help optimize immuno- and radiotherapy efficacy in translationally relevant syngeneic mouse tumor models.

CAIX-targeting radiotracers for hypoxia imaging in head and neck cancer models

Hypoxia-induced carbonic anhydrase IX (CAIX) expression is a prognostic marker in solid tumors. In recent years many radiotracers have been developed, but a fair comparison of these compounds is not possible because of the diversity in tumor models and other experimental parameters. In this study we performed a direct in vivo comparison of three promising CAIX targeting radiotracers in xenografted head and neck cancer models. The biodistribution of [¹¹¹In]In-DOTA-ZCAIX:2 was directly compared with [¹¹¹In]In-DTPA-G250-F(ab′)₂ and [¹¹¹In] In-DTPA-G250 in female BALB/C nu/nu mice bearing two HNSCC xenografts with different levels of CAIX expression. In vivo biodistribution was quantified by means of microSPECT/CT scans and ex vivo biodistribution was determined with the use of a γ-counter. Tumors were snap frozen and sections were stained for CAIX expression, vessels, hypoxia (pimonidazole) and tumor blood perfusion. Tracer uptake was significantly higher in SSCNij153 tumors compared to SCCNij185 tumors for [¹¹¹In]In-DOTA-HE3-ZCAIX:2: 0.32 ± 0.03 versus 0.18 ± 0.01%ID/g,(p = 0.003) 4 h p.i., for [¹¹¹In]In-DTPA-girentuximab-F(ab′)₂: 3.0 ± 0.5%ID/g and 1.2 ± 0.1%ID/g (p = 0.03), 24 h p.i. and for [¹¹¹In]In-DTPA-girentuximab: 30 ± 2.1%ID/g and 7.0 ± 1.0%ID/g (p = 0.0002) 72 h p.i. SPECT imaging with both [¹¹¹In]In-DTPA-girentuximab-F(ab′)₂ and [¹¹¹In]In-DTPA-girentuximab showed a clear difference in tracer distribution between the two tumor models. The whole IgG, i.e. [¹¹¹In]In-DTPA-girentuximab, showed the highest tumor-to-muscle ratio. We showed that different CAIX-targeting radiotracers can discriminate a low CAIX-expressing tumor from a high CAIX-expressing head and neck cancer xenografts model. In these hypoxic head and neck xenograft models [¹¹¹In]In-DTPA-girentuximab showed the most promising results.

Investigation of the preservation effect of canagliflozin on pancreatic beta cell mass using SPECT/CT imaging with 111In-labeled exendin-4

Radiolabeled exendin derivatives are promising for non-invasive quantification of pancreatic beta cell mass (BCM); longitudinal observation of BCM for evaluation of therapeutic effects has not been achieved. The aim of this study is to demonstrate the usefulness of our developing method using [Lys¹²(¹¹¹In-BnDTPA-Ahx)]exendin-4 to detect longitudinal changes in BCM. We performed a longitudinal study with obese type 2 diabetes model (db/db) mice administered canagliflozin, which is reported to preserve BCM. Six-week-old mice were assigned to a canagliflozin-administered group or a control group. Blood glucose levels of the canagliflozin group were significantly lower than those of the control group. Plasma insulin levels, insulin secretion during OGTT and insulin content in the pancreas were preserved in the canagliflozin group in comparison with those in the control group. According to SPECT/CT imaging analysis using [Lys¹²(¹¹¹In-BnDTPA-Ahx)]exendin-4, pancreatic uptake was significantly decreased in the control group, whereas there was no significant change in the canagliflozin group. After nine weeks, both pancreatic uptake and BCM of the canagliflozin group were significantly higher than those of the control group, and a correlation between them was observed. In conclusion, our imaging method confirmed the BCM-preservation effect of canagliflozin, and demonstrated its potential for longitudinal evaluation of BCM.

Quantitative Imaging of the Hypoxia-Related Marker CAIX in Head and Neck Squamous Cell Carcinoma Xenograft Models

Tumor hypoxia plays a major role in radio- and chemotherapy resistance in solid tumors. Carbonic Anhydrase IX (CAIX) is an endogenous hypoxia-related protein, which is associated with poor patient outcome. The quantitative assessment of CAIX expression of tumors may steer cancer treatment by predicting therapy response or patient selection for antihypoxia or CAIX-targeted treatment. Recently, the single-photon emission computerized tomography (SPECT) tracer [¹¹¹In]In-DTPA-girentuximab-F(ab′)₂ was developed and validated for targeting CAIX. The aim of this study was to optimize quantitative microSPECT/CT of CAIX expression in vivo in head and neck tumor models. Athymic mice with subcutaneous SCCNij153 and SCCNij202 head and neck squamous cell carcinoma xenografts were injected with [¹¹¹In]In-DTPA-girentuximab-F(ab′)₂. First, the protein dose, timing, and image acquisition settings were optimized. Tracer uptake was determined by quantitative SPECT, ex vivo radioactivity counting, and by autoradiography of tumor sections. The same tumor sections were immunohistochemically stained for CAIX expression and hypoxia. Highest tumor-normal-tissue contrast was obtained at 24 h after injection of the tracer. A protein dose of 10 μg resulted in the highest tumor-to-muscle ratio at 24 h p.i. Ex vivo biodistribution studies showed a tumor uptake of 3.0 ± 0.6%ID/g and a tumor-to-muscle ratio of 8.7 ± 1.4 (SCCNij153). Quantitative analysis of the SPECT images enabled us to distinguish CAIX antigen blocked from nonblocked tumors, fractions positive for CAIX expression: 0.22 ± 0.02 versus 0.08 ± 0.01 (p < 0.01). Immunohistochemical, autoradiographic, and microSPECT/CT analyses showed a distinct intratumoral spatial correlation between localization of the radiotracer and CAIX expression. Here, we demonstrate that [¹¹¹In]In-DTPA-girentuximab-F(ab′)₂ specifically targets CAIX-expressing cells in head and neck cancer xenografts. SPECT imaging with indium-labeled girentuximab-F(ab′)₂ allows quantitative assessment of the fraction of CAIX positive tissue in head and neck cancer xenografts. These results indicate that [¹¹¹In]In-DTPA-girentuximab-F(ab′)₂ is a promising tracer to image hypoxia-related CAIX expression.

Hypoxia Regulation of Phosphokinases and the Prognostic Value of pAKT in Breast Cancer

Tumor hypoxia results in poor treatment response and is an indicator of poor outcome in cancer patients. TRIB3 is a hypoxia-upregulated protein involved in the ability of breast cancer cells to survive in hypoxic conditions. It is also involved in the prognosis of cancer patients, possibly by affecting several kinase-signaling pathways. We set out to establish which kinase-signaling pathways are regulated by hypoxia and whether these kinases are relevant for breast cancer prognosis. Using a phosphokinase antibody array comparing cells cultured under hypoxic conditions with those cultured during normoxia, we found that the phosphorylation status of ERK1/2, AKT, p70 S6 kinase, Lck and STAT3 was altered in both MCF7 and MDA-MB-231 breast cancer cells. Using Western blotting, we found that phosphorylated AKT (pAKT) increased in hypoxic conditions. Knockdown of TRIB3 attenuated this effect of hypoxia on AKT activation. Both pAKT and TRIB3 were expressed in pimonidazole-positive, hypoxic areas of human breast cancer tumors. In breast cancer patients significantly lower 5-year disease-free survival was observed for the pAKT-positive compared to the pAKT-negative group (64.6% vs 86.1%, p=0.03).

In conclusion, the phosphorylation status of AKT is increased in hypoxic conditions and TRIB3 knockdown attenuates this response. Furthermore, pAKT expression denotes a worse prognosis in breast cancer patients. The hypoxia-related activation of AKT could explain the resistance to various treatments including chemotherapy and radiotherapy.

PET of EGFR with (64) Cu-cetuximab-F(ab')2 in mice with head and neck squamous cell carcinoma xenografts

Overexpression of the epidermal growth factor receptor (EGFR) is linked to an adverse outcome in various solid tumors. Cetuximab is an EGFR inhibitor, which in combination with radiotherapy improves locoregional control and survival in a subgroup of patients with head and neck squamous cell carcinomas (HNSCCs). The aim of this study was to develop and characterize an EGFR-directed PET tracer, (64) Cu-cetuximab-F(ab')2, to determine the systemic accessibility of EGFR. Mice with HNSCC xenografts, UT-SCC-8 (n = 6) or UT-SCC-45 (n = 6), were imaged 24 h post injection with (64) Cu-NODAGA-cetuximab-F(ab')2 using PET/CT. One mouse for each tumor model was co-injected with excess unlabeled cetuximab 3 days before radiotracer injection to determine non-EGFR-mediated uptake. Ex vivo biodistribution of the tracer was determined and tumors were analyzed by autoradiography and immunohistochemistry. The SUVmax of UT-SCC-8 tumors was higher than that of UT-SCC-45: 1.5 ± 1.0 and 0.8 ± 0.2 (p < 0.05), respectively. SUVmax after in vivo blocking of EGFR with cetuximab was 0.4. Immunohistochemistry showed that UT-SCC-8 had a significantly higher EGFR expression than UT-SCC-45: 0.50 ± 0.19 versus 0.12 ± 0.08 (p < 0.005), respectively. Autoradiography indicated that (64) Cu-cetuximab-F(ab')2 uptake correlated with EGFR expression in both tumors: r = 0.86 ± 0.06 (UT-SCC-8) and 0.90 ± 0.06 (UT-SCC-45). (64) Cu-cetuximab-F(ab')2 is a promising PET tracer to determine expression of EGFR in vivo. Clinically, this tracer has the potential to be used to determine cetuximab targeting of tumors and possibly to non-invasively monitor the response to EGFR-inhibitor treatment.

111In-cetuximab-F(ab')2 SPECT and 18F-FDG PET for prediction and response monitoring of combined-modality treatment of human head and neck carcinomas in a mouse model

Treatment of head and neck squamous cell carcinomas with radiotherapy and the epidermal growth factor receptor (EGFR) inhibitor cetuximab shows an improved response in a subgroup of patients. The aim of this study was to noninvasively monitor treatment response by visualizing systemically accessible EGFR with (111)In-cetuximab-F(ab')2 while simultaneously evaluating tumor metabolism with (18)F-FDG PET during combined-modality treatment.

METHODS

Eighty mice with patient-derived head and neck squamous cell carcinomas xenografts, SCCNij202 or SCCNij185, were imaged with SPECT/CT using (111)In-cetuximab-F(ab')2 (5 μg, 28 ± 6.1 MBq, 24 h after injection), followed by PET imaging with (18)F-FDG (9.4 ± 2.9 MBq, 1 h after injection). Scans were acquired on mice 10 d before treatment with either single-dose irradiation (10 Gy), cetuximab alone, or cetuximab-plus-irradiation combined or on untreated control mice. Scans were repeated 18 d after treatment. Tumor growth was monitored up to 120 d after treatment. EGFR expression was evaluated immunohistochemically.

RESULTS

SCCNij202 responded to combined treatment (P < 0.01) and cetuximab treatment alone (P < 0.05) but not to irradiation alone (P = 0.13). SCCNij185 responded to combined treatment (P < 0.05) and irradiation (P < 0.05) but not to cetuximab treatment alone (P = 0.34). (111)In-cetuximab-F(ab')2 uptake (tumor-to-liver ratio, scan 2 - scan 1) predicted response to therapy. A positive response to treatment significantly correlated with a reduced tracer uptake in the tumor in the second SPECT scan, compared with the first scan (P < 0.005 and <0.05 for SCCNij202 and SCCNij185, respectively). Resistance to therapy was characterized by a significantly increased (111)In-cetuximab-F(ab')2 tumor uptake; tumor-to-liver ratio was 2.2 ± 0.6 to 3.5 ± 1.2, P < 0.01, for (irradiated) SCCNij202 and 1.4 ± 0.4 to 2.0 ± 0.3, P < 0.05, for (cetuximab-treated) SCCNij185, respectively. (18)F-FDG PET tumor uptake (maximum standardized uptake value, scan 2 - scan 1) correlated with tumor response for SCCNij202 (P < 0.01) but not for SCCNij185 (P = 0.66). EGFR fractions were significantly different: 0.9 ± 0.1 (SCCNij202) and 0.5 ± 0.1 (SCCNij185) (P < 0.001). The EGFR fraction was significantly lower for irradiated SCCNij202 tumors than for controls (P < 0.005).

CONCLUSION

(111)In-cetuximab-F(ab')2 predicted and monitored the effects of EGFR inhibition or irradiation during treatment in both head and neck carcinoma models investigated, whereas (18)F-FDG PET only correlated with tumor response in the SCCNij202 model. Thus, the additional value of the (111)In-cetuximab-F(ab')2 tracer is emphasized and the tracer can aid in evaluating future treatments with EGFR-targeted therapies.

Early response monitoring with 18F-FDG PET and cetuximab-F(ab')2-SPECT after radiotherapy of human head and neck squamous cell carcinomas in a mouse model

Only a subset of patients with head and neck squamous cell carcinomas (HNSCCs) benefit from radiotherapy and concurrent epidermal growth factor receptor (EGFR) inhibitor therapy with cetuximab, indicating the need for patient selection. The aim of this study was to visualize the change in systemically accessible EGFR with (111)In-cetuximab-F(ab')2 SPECT before and after radiotherapy, while simultaneously evaluating (18)F-FDG PET uptake.

METHODS

Mice with HNSCC xenografts, cetuximab-sensitive SCCNij202 and cetuximab-resistant SCCNij167, were imaged with SPECT/CT using (111)In-cetuximab-F(ab')2 as a tracer, directly followed by PET imaging with (18)F-FDG. Scans were acquired 7 d before radiotherapy (10 Gy) and 1, 7, and 14 d after treatment. Intratumoral localization of (111)In-cetuximab-F(ab')(2) was evaluated by autoradiography and histologic markers evaluated by immunofluorescence staining in the same tumor sections.

RESULTS

Growth of irradiated SCCNij202 and SCCNij167 tumors was significantly delayed, compared with controls (P < 0.05). No changes in uptake of (18)F-FDG were observed in either of the xenografts after radiotherapy. SPECT images of tumor-bearing mice showed a significant increase in uptake of (111)In-cetuximab-F(ab')(2) in the SCCNij202 tumors after irradiation (tumor-to-liver ratio, 4.3 ± 1.1 vs. 10.5 ± 3.3, 7 d before and 14 d after treatment, respectively, P < 0.01) but not in SCCNij167 tumors. Immunohistochemical EGFR staining showed a translocation of the EGFR from the cytoplasm to the cell membrane in irradiated SCCNij202 xenografts. Intratumoral distribution of (111)In-cetuximab-F(ab')(2) as determined by autoradiography correlated well with the distribution of EGFR as determined immunohistochemically (r = 0.85; range, 0.69-0.95).

CONCLUSION

EGFR accessibility can be visualized with (111)In-cetuximab-F(ab')(2). (111)In-cetuximab-F(ab')(2) uptake increased after irradiation only in cetuximab-sensitive SCCNij202 xenografts, implying that the tracer can be used to measure irradiation-induced changes of EGFR expression and can monitor the compensatory response of tumors to radiotherapy.

Registration of whole immunohistochemical slide images: an efficient way to characterize biomarker colocalization

BACKGROUND AND OBJECTIVE

Extracting accurate information from complex biological processes involved in diseases, such as cancers, requires the simultaneous targeting of multiple proteins and locating their respective expression in tissue samples. This information can be collected by imaging and registering adjacent sections from the same tissue sample and stained by immunohistochemistry (IHC). Registration accuracy should be on the scale of a few cells to enable protein colocalization to be assessed.

METHODS

We propose a simple and efficient method based on the open-source elastix framework to register virtual slides of adjacent sections from the same tissue sample. We characterize registration accuracies for different types of tissue and IHC staining.

RESULTS

Our results indicate that this technique is suitable for the evaluation of the colocalization of biomarkers on the scale of a few cells. We also show that using this technique in conjunction with a sequential IHC labeling and erasing technique offers improved registration accuracies.

DISCUSSION

Brightfield IHC enables to address the problem of large series of tissue samples, which are usually required in clinical research. However, this approach, which is simple at the tissue processing level, requires challenging image analysis processes, such as accurate registration, to view and extract the protein colocalization information.

CONCLUSIONS

The method proposed in this work enables accurate registration (on the scale of a few cells) of virtual slides of adjacent tissue sections on which the expression of different proteins is evidenced by standard IHC. Furthermore, combining our method with a sequential labeling and erasing technique enables cell-scale colocalization.

Non-invasive quantification of the beta cell mass by SPECT with ¹¹¹In-labelled exendin

AIMS/HYPOTHESIS

A reliable method for in vivo quantification of pancreatic beta cell mass (BCM) could lead to further insight into the pathophysiology of diabetes. The glucagon-like peptide 1 receptor, abundantly expressed on beta cells, may be a suitable target for imaging. We investigated the potential of radiotracer imaging with the GLP-1 analogue exendin labelled with indium-111 for determination of BCM in vivo in a rodent model of beta cell loss and in patients with type 1 diabetes and healthy individuals.

METHODS

The targeting of (111)In-labelled exendin was examined in a rat model of alloxan-induced beta cell loss. Rats were injected with 15 MBq (111)In-labelled exendin and single photon emission computed tomography (SPECT) acquisition was performed 1 h post injection, followed by dissection, biodistribution and ex vivo autoradiography studies of pancreatic sections. BCM was determined by morphometric analysis after staining with an anti-insulin antibody. For clinical evaluation SPECT was acquired 4, 24 and 48 h after injection of 150 MBq (111)In-labelled exendin in five patients with type 1 diabetes and five healthy individuals. The tracer uptake was determined by quantitative analysis of the SPECT images.

RESULTS

In rats, (111)In-labelled exendin specifically targets the beta cells and pancreatic uptake is highly correlated with BCM. In humans, the pancreas was visible in SPECT images and the pancreatic uptake showed high interindividual variation with a substantially lower uptake in patients with type 1 diabetes.

CONCLUSIONS/INTERPRETATION

These studies indicate that (111)In-labelled exendin may be suitable for non-invasive quantification of BCM.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01825148, EudraCT: 2012-000619-10.

Prognostic value of the proliferation marker Ki-67 in laryngeal carcinoma: results of the accelerated radiotherapy with carbogen breathing and nicotinamide phase III randomized trial

BACKGROUND

The prognostic and predictive value of the proliferation marker Ki-67 was investigated in a randomized trial comparing accelerated radiotherapy with carbogen breathing and nicotinamide (ARCON) to accelerated radiotherapy in laryngeal carcinoma.

METHODS

Labeling index of Ki-67 (Li Ki-67) in immunohistochemically stained biopsies and the colocalization with carbonic anhydrase IX (CAIX) were related to tumor control and patient survival.

RESULTS

On average, node-positive patients had a higher Li Ki-67 (median 14% vs 8%; p < .01). In patients with a high Li Ki-67, the 5-year regional control and metastases-free survival were 79% versus 96% (p < .01) and 71% versus 88% (p = .05) for accelerated radiotherapy and ARCON, respectively. The 5-year local control and disease-specific survival were not significantly different. Patients with low Ki-67 expression had an excellent outcome with accelerated radiotherapy alone.

CONCLUSION

Patients with laryngeal carcinomas with high proliferative activity are at increased risk of regional and distant metastases formation. This risk can be reduced by treatment with ARCON.

Imaging of epidermal growth factor receptor expression in head and neck cancer with SPECT/CT and 111In-labeled cetuximab-F(ab')2

Combined treatment of advanced head and neck squamous cell carcinomas (HNSCC) with radiotherapy and the epidermal growth factor receptor (EGFR) inhibitor cetuximab improves clinical outcome in comparison to radiotherapy alone but is effective only in a few cases. To select those patients most likely to benefit from EGFR inhibition, it can be advantageous to quantify the tumor EGFR status before and possibly during therapy. The aim of this study was to develop and characterize the (111)In-cetuximab-F(ab')2 tracer to image EGFR targeting in vivo.

METHODS

The affinity and internalization kinetics of (111)In-cetuximab-F(ab')2 were determined in vitro. The optimal protein-fragment dose for imaging was determined in nude mice with a subcutaneous head and neck carcinoma model (FaDu). Mice with FaDu tumors were imaged using ultra-high-resolution SPECT with (111)In-cetuximab-F(ab')2 or (111)In-cetuximab IgG at 4, 24, 48, and 168 h after injection. Tumor tracer uptake was determined on micro-SPECT and autoradiography images of tumor sections. Immunohistochemical staining was used to analyze EGFR expression in the tumor.

RESULTS

In vitro, more than 50% of (111)In-cetuximab-F(ab')2 was internalized into FaDu cells within 24 h. The half maximal inhibitory concentration (IC50) of (111)In-cetuximab-F(ab')2 and (111)In-cetuximab was similar: 0.42 ± 0.16 nM versus 0.28 ± 0.14 nM, respectively. The protein dose-escalation study showed that the highest uptake of (111)In-cetuximab-F(ab')2 in tumors was obtained at doses of 10 μg/mouse or less (13.5 ± 5.2 percentage injected dose per gram [%ID/g]). Tumor uptake of (111)In-cetuximab was significantly higher (26.9 ± 3.3 %ID/g, P < 0.01). However, because of rapid blood clearance, tumor-to-blood ratios at 24 h after injection were significantly higher for (111)In-cetuximab-F(ab')2 (31.4 ± 3.8 vs. 1.7 ± 0.2, respectively; P < 0.001). The intratumoral distribution of (111)In-cetuximab-F(ab')2 correlated well with the immunohistochemical distribution of EGFR (r = 0.64 ± 0.06, P < 0.0001). micro-SPECT images of (111)In-cetuximab-F(ab')2 clearly showed preferential uptake in the tumor from 4 h onward, with superior tumor-to-background contrast at 24 h, compared with (111)In-cetuximab (107.0 ± 17.0 vs. 69.7 ± 3.9, respectively; P < 0.05).

CONCLUSION

(111)In-cetuximab-F(ab')2 displays higher tumor-to-blood ratios early after injection than (111)In-cetuximab in an HNSCC model, making it more suitable for EGFR visualization and potentially for selecting patients for treatment with EGFR inhibitors.

Prognostic value of Musashi-1 in gliomas

The aim of this study was to investigate the prognostic value of the RNA-binding protein Musashi-1 in adult patients with primary gliomas. Musashi-1 has been suggested to be a cancer stem cell-related marker in gliomas, and high levels of Musashi-1 have been associated with high tumor grades and hence poor prognosis. Samples of 241 gliomas diagnosed between 2005 and 2009 were stained with an anti-Musashi-1 antibody using a fluorescent staining protocol followed by automated image acquisition and processing. Musashi-1 area fraction and intensity in cytoplasm and in nuclei were quantified by systematic random sampling in 2 % of the vital tumor area. In WHO grade III tumors high levels of Musashi-1 were associated with poor survival in multivariate analysis (HR 3.39, p = 0.02). We identified a sub-population of glioblastoma (GBM) patients with high levels of Musashi-1 and a superior prognosis (HR 0.65, p = 0.038). In addition patients with high levels of Musashi-1 benefitted most from post-surgical treatment, indicating that Musashi-1 may be a predictive marker in GBMs. In conclusion, our results suggest that high levels of Musashi-1 are associated with poor survival in patients with WHO grade III tumors and that Musashi-1 may be a predictive marker in GBMs, although further validation is needed. We find the combination of immunofluorescence and automated quantitation to be a feasible, robust, and reproducible approach for quantitative biomarker studies.

111In-cetuximab-F(ab')2 SPECT imaging for quantification of accessible epidermal growth factor receptors (EGFR) in HNSCC xenografts

BACKGROUND AND PURPOSE

Immunohistochemical epidermal growth factor receptor (EGFR) expression does not correlate with treatment response in head and neck squamous cell carcinomas (HNSCC). Aim was to apply the tracer (111)In-cetuximab-F(ab')2 for EGFR microSPECT imaging and to investigate if tracer uptake correlated with response to EGFR-inhibition by cetuximab in HNSCC xenografts. Usage of F(ab)2 fragments allows for shorter interval between tracer injection and imaging.

MATERIALS AND METHODS

Mice with HNSCC xenografts, SCCNij202, 153, 185 and 167 were imaged with microSPECT using (111)In-cetuximab-F(ab')2. Subsequently, tumors were analyzed by autoradiography and immunohistochemistry and tracer concentration was determined. Tumor uptake was correlated with previously assessed response to cetuximab treatment.

RESULTS

MicroSPECT imaging showed preferential uptake in HNSCC xenografts. Tumor-to-liver ratios were 3.1 ± 0.2 (SCCNij202), 2.8 ± 0.4 (SCCNij153), 2.0 ± 0.8 (SCCNij185), 2.0 ± 0.4 (SCCNij167). Immunohistochemical EGFR fractions (fEGFR) differed significantly between xenografts; 0.77 ± 0.07 (SCCNij202), 0.66 ± 0.11 (SCCNij153), 0.57 ± 0.19 (SCCNij185), 0.16 ± 0.10 (SCCNij167) (p < 0.001). Tumor fEGFR correlated with (111)In-cetuximab-F(ab')2 tumor uptake (r = 0.6, p < 0.01) and tracer autoradiography (r = 0.7, p < 0.0001). Tumor uptake of (111)In-cetuximab-F(ab')2 was proportionally associated with cetuximab treatment response in three out of four xenograft models.

CONCLUSION

(111)In-cetuximab-F(ab')2 showed good tumor-to-background contrast on microSPECT imaging, allowing noninvasive assessment of EGFR expression in vivo, and possibly evaluation of treatment response to EGFR-inhibition.

Pattern of CAIX expression is prognostic for outcome and predicts response to ARCON in patients with laryngeal cancer treated in a phase III randomized trial

BACKGROUND AND PURPOSE

In a phase III trial in patients with advanced stage laryngeal carcinoma comparing ARCON (accelerated radiotherapy with carbogen breathing and nicotinamide) to accelerated radiotherapy alone (AR) the prognostic and predictive value of CAIX, a hypoxia-associated protein, was investigated.

MATERIAL AND METHODS

261 Paraffin embedded tumor biopsies and 79 fresh frozen biopsies from patients entered in the trial were immunohistochemically stained for CAIX. CAIX-fraction and CAIX expression pattern were related to tumor control and patient survival.

RESULTS

Low CAIX-fraction was prognostic for worse regional control and overall survival in patients treated with AR. Patients with a low CAIX-fraction treated with ARCON had better regional control and metastasis-free survival compared to AR (RC 97% vs 71%, p < 0.01 and MFS 92% vs 69%, p = 0.06). Patients with a perinecrotic CAIX staining pattern had a significantly worse local control, metastasis-free and overall survival compared to patients with a diffuse pattern (65% vs 84%, p = 0.01, 70% vs 96%, p < 0.01 and 42% vs 71%, p < 0.01 respectively), and this could not be improved with ARCON. After multivariate analysis CAIX pattern and N-stage emerged as significant predictors for metastasis-free survival and overall survival.

CONCLUSIONS

ARCON improves regional control and metastasis-free survival only in patients with low CAIX expression. The different patterns of CAIX expression suggest different mechanisms of upregulation and have important prognostic value.

Monitoring the effects of bevacizumab beyond progression in a murine colorectal cancer model: a functional imaging approach

Clinical studies have shown that bevacizumab beyond progression to first line therapy is beneficial for overall survival in advanced stage colorectal cancer. We studied the utility of several functional imaging modalities to assess the efficacy of bevacizumab beyond progression (BBP). All BALB/c mice with s.c. LS174T xenografts were treated with capecitabine, oxaliplatin and bevacizumab combination therapy. Tumor volume was assessed using caliper measurements. Increase of 1.5 times the initial volume on two subsequent measurements, was considered progression. In half of the mice bevacizumab treatment was continued (n = 13) after progressive disease was established, while the others received saline injections (n = 12). Within 3 days after progression, multi-modal imaging was performed using FDG-PET, diffusion weighted imaging, T2* and dynamic contrast enhanced MRI. Measurements were repeated 7 and 10 days after the first measurements. Afterwards, tumors were analyzed for expression of carbonic anhydrase IX, glucose transporter 1, 9 F1 to stain the vasculature and Ki67 to assess proliferation. In the BBP group tumor growth after progression was reduced compared to the control group (p < 0.01). FDG-PET showed a trend towards lower FDG uptake in the BBP group (p = 0.08). DWI, T2* and DCE-MRI parameters were not significantly different between both groups. The immunohistochemical analyses showed higher CAIX-positive fraction (p < 0.01) and lower Ki67 expression (p = 0.06) in the BBP group. The relative vascular area was significantly lower in the BBP group (p = 0.03). GLUT-1 expression and vascular density did not significantly differ between both groups. Bevacizumab after progression resulted in significant changes in the tumor proliferation and microenvironment compared to discontinuation of bevacizumab. FDG-PET may be sensitive to BBP-induced effects.

Reproducibility and biological basis of in vivo T(2)* magnetic resonance imaging of liver metastasis of colorectal cancer

In this study, the reproducibility of T2* MR imaging in colorectal liver metastases was assessed and T2* values were correlated with the expression of the hypoxia-related markers GLUT-1 and CA-IX as well as the relative vascular area, and the vessel density in resected tumors. The reproducibility of T2* was analyzed in 18 patients with in total 22 colorectal liver metastases using the Bland and Altman method for the 16th, 50th, and 84th percentile values. Immunohistochemical staining was performed on 17 resected tumors obtained from 16 patients. The median T2* of all liver metastases was 25.0 ± 5.6 ms vs. 23.0 ± 4.1 ms (median ± st.dev.) in normal liver. The coefficient of repeatability was 11.2 ms and the limits of agreement were -13.2 ms and 9.1 ms for median T2* values. On average, T2* showed fair reproducibility. No correlations between T2* values, hypoxia- and vascularity-related markers were observed.

Diffusion-weighted MR imaging in liver metastases of colorectal cancer: reproducibility and biological validation

OBJECTIVES

Before diffusion-weighted imaging (DWI) can be implemented in standard clinical practice for response monitoring, data on reproducibility are needed to assess which differences outside the range of normal variation can be detected in an individual patient. In this study we assessed the reproducibility of the apparent diffusion coefficient (ADC) values in colorectal liver metastases. To provide a biological basis for these values, their relation with histopathology was assessed.

METHODS

DWI was performed twice in 1 week in patients scheduled for metastasectomy of colorectal liver metastases. Correlation between ADC values and apoptosis marker p53, anti-apoptotic protein BCL-2, proliferation marker Ki67 and serum vascular endothelial growth factor (VEGF) concentration were assessed.

RESULTS

A good reproducibility coefficient of the mean ADC (coefficient of reproducibility 0.20 × 10(-3) mm(2)/s) was observed in colorectal liver metastases (n = 21). The ADC value was related to the proliferation index and BCL-2 expression of the metastases. Furthermore, in metastases recently treated with systemic therapy, the ADC was significantly higher (1.27 × 10(-3) mm(2)/s vs 1.05 × 10(-3) mm(2)/s, P = 0.02).

CONCLUSIONS

The good reproducibility, correlation with histopathology and implied sensitivity for systemic treatment-induced anti-tumour effects suggest that DWI might be an excellent tool to monitor response in metastatic colorectal cancer.

Reproducibility of functional volume and activity concentration in 18F-FDG PET/CT of liver metastases in colorectal cancer

PURPOSE

Several studies showed potential for monitoring response to systemic therapy in metastatic colorectal cancer patients with (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET). Before (18)F-FDG PET can be implemented for response evaluation the repeatability should be known. This study was performed to assess the magnitude of the changes in standardized uptake value (SUV), volume and total lesion glycolysis (TLG) in colorectal liver metastases and validate the biological basis of (18)F-FDG PET in colorectal liver metastases.

METHODS

Twenty patients scheduled for liver metastasectomy underwent two (18)F-FDG PET scans within 1 week. Bland-Altman analysis was performed to assess repeatability of SUV(max), SUV(mean), volume and TLG. Tumours were delineated using an adaptive threshold method (PET(SBR)) and a semiautomatic fuzzy locally adaptive Bayesian (FLAB) delineation method.

RESULTS

Coefficient of repeatability of SUV(max) and SUV(mean) were ∼39 and ∼31 %, respectively, independent of the delineation method used and image reconstruction parameters. However, repeatability was worse in recently treated patients. The FLAB delineation method improved the repeatability of the volume and TLG measurements compared to PET(SBR), from coefficients of repeatability of over 85 % to 45 % and 57 % for volume and TLG, respectively. Glucose transporter 1 (GLUT1) expression correlated to the SUV(mean). Vascularity (CD34 expression) and tumour hypoxia (carbonic anhydrase IX expression) did not correlate with (18)F-FDG PET parameters.

CONCLUSION

In conclusion, repeatability of SUV(mean) and SUV(max) was mainly affected by preceding systemic therapy. The repeatability of tumour volume and TLG could be improved using more advanced and robust delineation approaches such as FLAB, which is recommended when (18)F-FDG PET is utilized for volume or TLG measurements. Improvement of repeatability of PET measurements, for instance by dynamic PET scanning protocols, is probably necessary to effectively use PET for early response monitoring.

Differences in metabolism between adeno- and squamous cell non-small cell lung carcinomas: spatial distribution and prognostic value of GLUT1 and MCT4

BACKGROUND

Hypoxia leads to changes in tumor cell metabolism such as increased glycolysis. In this study, we examined the spatial distribution of the glycolysis and hypoxia related markers glucose transporter 1 (GLUT1) and monocarboxylate transporter 4 (MCT4) expression in relation to the vasculature in stage I, II and resectable stage IIIA NSCLC. Furthermore, associations of these markers with survival were investigated.

METHODS

GLUT1 and MCT4 expression were determined in 90 NSCLC fresh frozen biopsies using immunohistochemical techniques and a computerized image analysis system. Markers were analyzed for adenocarcinomas (n=41) and squamous cell carcinomas (n=34) separately. Eighty-four patients were retrospectively evaluated for relapse and survival.

RESULTS

Squamous cell carcinomas demonstrated higher GLUT1 expression, relative to adenocarcinomas. Also, in squamous cell carcinomas, GLUT1 and MCT4 expression increased with increasing distance from the vasculature, whereas in adenocarcinomas upregulation of MCT4 was already found at closer distance from vessels. In adenocarcinomas, high GLUT1 expression correlated with a poor differentiation grade and positive lymph nodes at diagnosis. High GLUT1 plus high MCT4 expression was associated with a poor disease-specific survival in only adenocarcinomas (p=0.032).

CONCLUSION

Analysis of GLUT1 and MCT4 expression on the histological level suggested a different metabolism for adenocarcinomas and squamous cell carcinomas. Likely, adenocarcinomas rely mainly on aerobic glycolysis for ATP production, whereas the behavior of squamous cell carcinomas is more physiologically, i.e. mitochondrial oxidation with anaerobic glycolysis under hypoxic conditions. High GLUT1 plus high MCT4 expression indicated an aggressive tumor behavior in adenocarcinomas. This subgroup of tumors may benefit from new treatment approaches, such as MCT4 inhibitors. Since this study has an exploratory character, our results warrant further investigation and need independent validation.