Antibody-Based Radionuclide Targeting for Diagnostics and Therapy : Preclinical Studies on Head and Neck Cancer

Antibody-based targeting techniques play an increasingly important role in cancer research. By targeting a structure that is abundant in tumour cells, but rare in healthy tissues, an antibody can mediate the delivery of radioactivity specifically to tumour cells in the body. This idea is particularly appealing for head and neck squamous cell carcinoma (HNSCC), as the advanced stages have a large fraction of spread disease that is difficult to treat with procedures available today. In this thesis, we have investigated possible radioimmunotargeting structures for HNSCC, and found that CD44v6 is a suitable target for antibody-based radiotherapy and diagnostics in this patient group. We have identified radiohalogens as attractive nuclides for such use, and have investigated the possibility of radiohalogenating the anti CD44v6 chimeric monoclonal antibody (cMAb) U36. Several feasible labelling methods were identified, using both direct and indirect labelling. The cMAb U36 was then successfully labelled with 211At and 131I, and preclinically evaluated for therapeutic use. Results proved the astatinated conjugate to be most efficient in this context, demonstrating a specific and dose-dependent cytotoxicity. The cMAb U36 was then evaluated for diagnostic use in thyroid anaplastic carcinoma, using 124I as the diagnostic nuclide. Results in tumour-bearing mice were promising, with all of the tumours identified in micro-PET studies. These results demonstrate how antibody-based radionuclide targeting can provide more sensitive and specific methods for identifying and treating head and neck cancer, and hopefully help improve long-term survival rates for this patient group in the future

Characterization and functionality of three head and neck squamous cell carcinoma cell lines and method optimization for use in future projects

Abstract The poor long term survival rate of head and neck squamous cell carcinoma is thought to partly be due to the high recurrence frequency caused by a small subset of cancer cells, the cancer stem cells. Several isoforms of CD44, a transmembrane protein, have been identified as possible cancer stem cell markers. In head and neck squamous cell carcinoma, the isoform of particular interest is CD44v6, which is expressed in the majority of malignancies. Therefore, characterization of head and neck cell lines is of increasing importance which is what brought about this project. Three cell lines; LK0412, UT45 and UT14, were characterized in regard to expression of CD44v6 under both normal and starvation conditions. The cell lines were also tested in different assays commonly used in research at the institution (Biomedicinsk Strålningsvetenskap), such as clonogenic assays. This was done in order to determine which of the cell lines would prove the most useful in future projects. The LK0412 cell line displayed the highest expression of CD44v6 and performed well in all assays. Starvation assays were performed for each cell line and aside from clonogenic assays, the LK0412 cell line was advantageous to use in comparison with the UT45 and UT14 cell lines. In addition, several of the assay methods were optimized for each cell line during the course of the study, which will help obtain more precise results during future projects using these cell lines. Huvud-och halscancer är den sjätte vanligaste cancerformen i världen med en låg överlevnadsutsikt på 30-50% inom tre år. Den höga dödligheten beror bland annat på en hög tendens till metastaser och återkomst av sjukdomen. Studier tyder på att endast en liten del av cancerceller, de så kallade cancerstamcellerna, har förmågan att metastasera. I huvud-och halscancer har ett förhöjt uttryck av ytproteinet CD44v6 associerats med cancerstamceller, vilket lett till ökad fokus på just detta protein inom cancerforskning. I denna studie karakteriserades tre cellinjer; LK0412, UT45 och UT14, utifrån deras uttryck av CD44v6 under både normala och svältförhållanden. Dessutom testades cellinjerna i olika experiment för att kunna etablera vilken av cellinjerna som skulle vara utav störst användning under framtida projekt på institutionen för Biomedicinsk Strålningsvetenskap. Den klart mest fördelaktiga cellinjen var LK0412. Cellinjen hade det högsta uttrycket av CD44v6 och producerade konsekvent bra resultat från övriga experiment. Det uppstod problem med både UT45 och UT14 i en del av experimenten trots försök till optimering av metoder och parametrar. I framtida projekt om CD44v6s betydelse för cancerstamcellsuttrycket i huvudoch halscancer, används därför med fördel cellinjen LK0412.

The radiosensitizer Onalespib increases complete remission in Lu-177-DOTATATE-treated mice bearing neuroendocrine tumor xenografts

Purpose: Lu-177-DOTATATE targeting the somatostatin receptor (SSTR) is utilized for treatment of neuroendocrine tumors (NETs). Onalespib, a heat shock protein 90 (HSP90) inhibitor, has demonstrated radiosensitizing properties and may thus enhance the effect of Lu-177-DOTATATE. Consequently, the aim of this study was to assess the potential of Onalespib in combination with Lu-177-DOTATATE in vivo and to examine the toxicity profiles of the treatments. Methods: Lu-177-DOTATATE selectivity and distribution in NET xenografts were studied using biodistribution and autoradiography. Therapeutic effects of Onalespib in combination with Lu-177-DOTATATE were studied in NET xenografts. Histological analyses were used to assess molecular effects from treatment and to establish toxicity profiles. Results: Biodistribution and autoradiography confirmed the SSTR-selective tumor uptake of Lu-177-DOTATATE, which was unaffected by Onalespib treatment. Immunohistochemistry verified molecular responses to Onalespib therapy in the tumors. While Onalespib and Lu-177-DOTATATE monotherapies resulted in a 10% and 33% delay in tumor doubling time compared with control, the combination treatment resulted in a 73% delayed tumor doubling time. Moreover, combination treatment increased complete remissions threefold from Lu-177-DOTATATE monotherapy, resulting in 29% complete remissions. In addition, histological analyses demonstrated radiation-induced glomerular injury in the Lu-177-DOTATATE monotherapy group. The damage was decreased tenfold in the combination group, potentially due to Onalespib-induced HSP70 upregulation in the kidneys. Conclusion: Treatment with Onalespib potentiated Lu-177-DOTATATE therapy of NET xenografts with a favorable toxicity profile. Utilizing Onalespib's radiosensitizing properties with Lu-177-DOTATATE may lead to better therapeutic results in the future and may reduce unwanted side effects in dose-limiting organs.De två första författarna delar förstaförfattarskapet.</p

Characterization of CD44 variant expression in head and neck squamous cell carcinomas

CD44 is a complex family of molecules, associated with aggressive malignancies and cancer stem cells. However, the role of CD44 variants in tumor progression and treatment resistance is not clear. In this study, the expression of CD44 and its variants was assessed in head and neck squamous cell carcinomas (HNSCC). Furthermore, subpopulations of cells expressing high amounts of CD44 variants were identified and characterized, for e.g., cell cycle phase and radioresistance. Results revealed high and homogenous CD44 and CD44v7 expression in four cell lines and CD44v4 and CD44v6 in three cell lines. CD44v3 was highly expressed in two cell lines, whereas CD44v5, CD44v7/8, CD44v10, CD133, and CD24 demonstrated no or moderate expression. Moreover, a subpopulation of very high CD44v4 expression was identified, which is independent of cell phase, demonstrating increased proliferation and radioresistance. In cell starvation experiments designed to enrich for cancer stem cells, a large population with dramatically increased expression of CD44, CD44v3, CD44v6, and CD44v7 was formed. Expression was independent of cell phase, and cells demonstrated increased radioresistance and migration rate. Our results demonstrate that the heterogeneity of tumor cells has important clinical implications for the treatment of HNSCC and that some of the CD44 variants may be associated with increased radioresistance. Highly expressed CD44 variants could make interesting candidates for selective cancer targeting

The HSP90 inhibitor onalespib potentiates Lu-177-DOTATATE therapy in neuroendocrine tumor cells

Lu-177-DOTATATE was recently approved for the treatment of somatostatin receptor (SSTR)-positive neuroen-docrine tumors (NETs). However, despite impressive response rates, complete responses are rare. Heat shock protein 90 (HSP90) inhibitors have been suggested as suitable therapeutic agents for NETs, as well as a potential radiosensitizers. Consequently, the aim of this study was to investigate whether the HSP90-inhibitor onalespib could reduce NET cell growth and act as a radiosensitizer when used in combination with Lu-177-DOTATATE. The NET cell lines BON, NCI-H727 and NCI-H460, were first characterized with regards to Lu-177-DOTATATE uptake and sensitivity to onalespib treatment in monolayer cell assays. The growth inhibitory effects of the monotherapies and combination treatments were then examined in three-dimensional multicellular tumor spheroids. Lastly, the molecular effects of the treatments were assessed. Lu-177-DOTATATE uptake was observed in the BON and NCI-H727 cells, while the NCI-H460 cells exhibited no detectable uptake. Accordingly, Lu-177-DOTATATE reduced the growth of BON and NCI-H727 spheroids, while no effect was observed in the NCI-H460 spheroids. Onalespib reduced cell viability and spheroid growth in all three cell lines. Furthermore, the combination of onalespib and Lu-177-DOTATATE exerted synergistic therapeutic effects on the BON and NCI-H727 spheroids. Western blot analysis of BON spheroids revealed the downregulation of epidermal growth factor receptor (EGFR) and the upregulation of gamma H2A histone family member X (gamma H2AX) following combined treatment with onalespib and Lu-177-DOTATATE. Moreover, flow cytometric analyses revealed a two-fold increase in caspase 3/7 activity in the combination group. In conclusion, the findings of this study demonstrate that onalespib exerts antitumorigenic effects on NET cells and may thus be a feasible treatment option for NETs. Furthermore, onalespib was able to synergistically potentiate Lu-177-DOTATATE treatment in a SSTR-specific manner. The radiosensitizing mechanisms of onalespib involved the downregulation of EGFR expression and the induction of apoptosis. Consequently, the combination of onalespib and Lu-177-DOTATATE may prove to be a promising strategy with which to improve therapeutic responses in patients with NETs. Further studies investigating this strategy in vivo regarding the therapeutic effects and potential toxicities are warranted to expand these promising findings

Improved sensitivity in hydrophilic interaction liquid chromatography-electrospray-mass spectrometry after removal of sodium and potassium ions from biological samples

Inorganic ions, such as sodium and potassium, are present in all biological matrices and are sometimes also added during sample preparation. However, these inorganic ions are known to hamper electrospray ionization -mass spectrometry (ESI-MS) applications, especially in hydrophilic interaction liquid chromatography (HILIC) where they are retained and can be detected as adducts and clusters with mobile phase components or analytes. The retention of inorganic ions leads to co-elution with analytes and as a result ion-suppression, extensive adduct formation and problems with reproducibility. In the presented work, a sample preparation method using cation exchange solid phase extraction (SPE) was developed to trap Na+ and K+ ions from human blood plasma and head and neck cancer cells for the analysis of small cationic, anionic as well as neutral organic analytes. The investigated analytes were small, hydrophilic compounds typically in focus in metabolomics studies. The samples were analyzed using full-scan HILIC-ESI-quadrupole time of flight (QTOF)-MS with an untargeted, screening approach. Method performance was evaluated using multivariate data analysis as well as relative quantifications, spiking of standards to evaluate linearity of response and post-column infusion to study ion-suppression. In blood plasma, the reduction of sodium and potassium ion concentration resulted in improved sensitivity increased signal intensity for 19 out of 28 investigated analytes, improved linearity of response, reduced ion-suppression and reduced cluster formation as well as adduct formation. Thus, the presented method has significant potential to improve data quality in metabolomics studies

Evaluation of cancer stem cell markers CD133, CD44, CD24 : association with AKT isoforms and radiation resistance in colon cancer cells.

The cell surface proteins CD133, CD24 and CD44 are putative markers for cancer stem cell populations in colon cancer, associated with aggressive cancer types and poor prognosis. It is important to understand how these markers may predict treatment outcomes, determined by factors such as radioresistance. The scope of this study was to assess the connection between EGFR, CD133, CD24, and CD44 (including isoforms) expression levels and radiation sensitivity, and furthermore analyze the influence of AKT isoforms on the expression patterns of these markers, to better understand the underlying molecular mechanisms in the cell. Three colon cancer cell-lines were used, HT-29, DLD-1, and HCT116, together with DLD-1 isogenic AKT knock-out cell-lines. All three cell-lines (HT-29, HCT116 and DLD-1) expressed varying amounts of CD133, CD24 and CD44 and the top ten percent of CD133 and CD44 expressing cells (CD133(high)/CD44(high)) were more resistant to gamma radiation than the ten percent with lowest expression (CD133(low)/CD44(low)). The AKT expression was lower in the fraction of cells with low CD133/CD44. Depletion of AKT1 or AKT2 using knock out cells showed for the first time that CD133 expression was associated with AKT1 but not AKT2, whereas the CD44 expression was influenced by the presence of either AKT1 or AKT2. There were several genes in the cell adhesion pathway which had significantly higher expression in the AKT2 KO cell-line compared to the AKT1 KO cell-line; however important genes in the epithelial to mesenchymal transition pathway (CDH1, VIM, TWIST1, SNAI1, SNAI2, ZEB1, ZEB2, FN1, FOXC2 and CDH2) did not differ. Our results demonstrate that CD133(high)/CD44(high) expressing colon cancer cells are associated with AKT and increased radiation resistance, and that different AKT isoforms have varying effects on the expression of cancer stem cell markers, which is an important consideration when targeting AKT in a clinical setting

Preclinical evaluation of a novel engineered recombinant human anti-CD44v6 antibody for potential use in radio-immunotherapy

CD44v6 is overexpressed in a variety of cancers, rendering it a promising target for radio-immunotherapy (RIT). In this study, we have characterized a novel engineered recombinant monoclonal anti-CD44v6 antibody, AbN44v6, and assessed its potential for use in RIT using either Lu-177 or I-131 as therapeutic radionuclides. In vitro affinity and specificity assays characterized the binding of the antibody labeled with Lu-177, I-125 or I-131. The therapeutic effects of Lu-177-AbN44v6 and I-131-AbN44v6 were investigated using two in vitro 3D tumor models with different CD44v6 expression. Finally, the normal tissue biodistribution and dosimetry for Lu-177-AbN44v6 and I-125-AbN44v6/I-131-AbN44v6 were assessed in vivo using a mouse model. All AbN44v6 radioconjugates demonstrated CD44v6-specific binding in vitro. In the in vitro 3D tumor models, dose-dependent therapeutic effects were observed with both Lu-177-AbN44v6 and I-131-AbN44v6, with a greater significant therapeutic effect observed on the cells with a higher CD44v6 expression. Biodistribution experiments demonstrated a greater uptake of Lu-177-AbN44v6 in the liver, spleen and bone, compared to I-125-AbN44v6, whereas I-125-AbN44v6 demonstrated a longer circulation time. In dosimetric calculations, the critical organs for Lu-177-AbN44v6 were the liver and spleen, whereas the kidneys and red marrow were considered the critical organs for I-131-AbN44v6. The effective dose was in the order of 0.1 mSv/MBq for both labels. In conclusion, AbN44v6 bound specifically and with high affinity to CD44v6. Furthermore, in vitro RIT demonstrated growth inhibition in a CD44v6-specific activity-dependent manner for both radioconjugates, demonstrating that both Lu-177-AbN44v6 and I-131-AbN44v6 may be promising RIT candidates. Furthermore, biodistribution and dosimetric analysis supported the applicability of both conjugates for RIT. The CD44v6-specific therapeutic effects observed with radiolabeled AbN44v6 in the 3D tumor models in vitro, combined with the beneficial dosimetry in vivo, render AbN44v6 a potential candidate for RIT

In vivo characterization of the novel CD44v6-targeting Fab fragment AbD15179 for molecular imaging of squamous cell carcinoma : a dual-isotope study

BACKGROUND: Patients with squamous cell carcinoma in the head and neck region (HNSCC) offer a diagnostic challenge due to difficulties to detect small tumours and metastases. Imaging methods available are not sufficient, and radio-immunodiagnostics could increase specificity and sensitivity of diagnostics. The objective of this study was to evaluate, for the first time, the in vivo properties of the radiolabelled CD44v6-targeting fragment AbD15179 and to assess its utility as a targeting agent for radio-immunodiagnostics of CD44v6-expressing tumours. METHODS: The fully human CD44v6-targeting Fab fragment AbD15179 was labelled with 111In or 125I, as models for radionuclides suitable for imaging with SPECT or PET. Species specificity, antigen specificity and internalization properties were first assessed in vitro. In vivo specificity and biodistribution were then evaluated in tumour-bearing mice using a dual-tumour and dual-isotope setup. RESULTS: Both species-specific and antigen-specific binding of the conjugates were demonstrated in vitro, with no detectable internalization. The in vivo studies demonstrated specific tumour binding and favourable tumour targeting properties for both conjugates, albeit with higher tumour uptake, slower tumour dissociation, higher tumour-to-blood ratio and higher CD44v6 sensitivity for the 111In-labelled fragment. In contrast, the 125I-Fab demonstrated more favourable tumour-to-organ ratios for liver, spleen and kidneys. CONCLUSIONS: We conclude that AbD15179 efficiently targets CD44v6-expressing squamous cell carcinoma xenografts, and particularly, the 111In-Fab displayed high and specific tumour uptake. CD44v6 emerges as a suitable target for radio-immunodiagnostics, and a fully human antibody fragment such as AbD15179 can enable further clinical imaging studies

Enhancing the therapeutic effects of in vitro targeted radionuclide therapy of 3D multicellular tumor spheroids using the novel stapled MDM2/X-p53 antagonist PM2

Background: Precision therapeutics continuously make advances in cancer therapy, and a field of growing interest is the combination of targeted radionuclide therapy (TRNT) with potential radiosensitizing agents. This study evaluated whether the effects of in vitro TRNT, using the Lu-177-labeled anti-CD44v6 antibody AbN44v6, were potentiated by the novel stapled MDM2/X-p53 antagonist PM2. Materials and methods: Two wt p53 cell lines, HCT116 (colorectal carcinoma) and UM-SCC-74B (head and neck squamous cell carcinoma), expressing different levels of the target antigen, CD44v6, were used. Antigen-specific binding of Lu-177-AbN44v6 was initially verified in a 2D cell assay, after which the potential effects of unlabeled AbN44v6 on downstream phosphorylation of Erk1/2 were evaluated by western blotting. Further, the therapeutic effects of unlabeled AbN44v6, Lu-177-AbN44v6, PM2, or a combination (labeled/unlabeled AbN44v6 +/- PM2) were assessed in 3D multicellular tumor spheroid assays. Results: Radiolabeled antibody bound specifically to CD44v6 on both cell lines. Unlabeled AbN44v6 binding did not induce downstream phosphorylation of Erk1/2 at any of the concentrations tested, and repeated treatments with the unlabeled antibody did not result in any spheroid growth inhibition. Lu-177-AbN44v6 impaired spheroid growth in a dose-dependent and antigen-dependent manner. A single modality treatment with 20 mu M of PM2 significantly impaired spheroid growth in both spheroid models. Furthermore, the combination of TRNT and PM2-based therapy proved significantly more potent than either monotherapy. In HCT116 spheroids, this resulted in a two- and threefold spheroid growth rate decrease for the combination of PM2 and 100 kBq Lu-177-AbN44v6 compared to monotherapies 14-day post treatment. In UM-SCC-74B spheroids, the combination therapy resulted in a reduction in spheroid size compared to the initial spheroid size 10-day post treatment. Conclusion: TRNT using Lu-177-AbN44v6 proved efficient in stalling spheroid growth in a dose-dependent and antigen-dependent manner, and PM2 treatment demonstrated a growth inhibitory effect as a monotherapy. Moreover, by combining TRNT with PM2-based therapy, therapeutic effects of TRNT were potentiated in a 3D multicellular tumor spheroid model. This proof-of-concept study exemplifies the strength and possibility of combining TRNT targeting CD44v6 with PM2-based therapy