The influence of cytotoxic drugs on the immunophenotype of blast cells in paediatric B precursor acute lymphoblastic leukaemia

BACKGROUND

Flow cytometry plays is important in the diagnosis of acute lymphoblastic leukaemia (ALL) and when antigen-specific immunotherapy is indicated. We have investigated the effects of prednisolone, vincristine, daunorubicin, asparaginase and methotrexate on the antigen expression on blast cells that could influence the planning of antigen-specific therapy as well as risk-based treatment assignment.

PATIENTS AND METHODS

Patients aged ≤ 17 years with de novo B-cell ALL (B-ALL) were enrolled in the study. Blast cells were isolated and exposed in vitro to 5 individual cytotoxic drugs in logarithmically increasing concentrations. Then, the expression of CD10, CD19, CD20, CD27, CD34, CD45, CD58, CD66c and CD137 antigens was determined by quantitative flow cytometry.

RESULTS

Cytotoxic drugs caused dose-dependent or dose-independent modulation of antigen expression. Daunorubicin caused a dose-dependent down-modulation of CD10, CD19, CD34, CD45 and CD58 and an up-modulation of CD137. Vincristine caused a dose-dependent down-modulation of CD19 and CD58 and an up-modulation of CD45. Daunorubicin also caused dose-independent down-modulation of CD27 and prednisolone down-modulation of CD10, CD19, CD27, CD34 and CD58. Down-modulation of CD20 was detected only in relation to the specific dose of daunorubicin.

CONCLUSIONS

The results of the study have shown that cytotoxic drugs can alter the expression of antigens that are important for immunotherapy. Importantly, daunorubicin, prednisolone and vincristine caused down-modulation of CD19 and CD58, suggesting that these drugs are better avoided during bridging therapy prior to bispecific antibodies or CAR-T cell therapy. In addition, immunophenotypic changes on blast cells induced by different drugs could also influence risk-based treatment assignment.

Electrochemotherapy combined with immunotherapy - a promising potential in the treatment of cancer

Electrochemotherapy is a novel, locoregional therapy that is used to treat cutaneous and deep-seated tumors. The electric pulses used in electrochemotherapy increase the permeability of the cell membranes of the target lesion and thus enhance the delivery of low-permeant cytotoxic drugs to the cells, leading to their death. It has also been postulated that electrochemotherapy acts as an in situ vaccination by inducing immunogenic cell death. This in turn leads to an enhanced systemic antitumor response, which could be further exploited by immunotherapy. However, only a few clinical studies have investigated the role of combined treatment in patients with melanoma, breast cancer, hepatocellular carcinoma, and cutaneous squamous cell carcinoma. In this review, we therefore aim to review the published preclinical evidence on combined treatment and to review clinical studies that have investigated the combined role of electrochemotherapy and immunotherapy.

In Vivo Wound Healing Model for Characterization of Gene Electrotransfer Effects in Mouse Skin

Wound healing is a complex biological response to injury characterized by a sequence of interdependent and overlapping physiological actions. To study wound healing and cutaneous regeneration processes, the complexity of wound healing requires the use of animal models. In this chapter, we describe the protocol to generate skin wounds in a mouse model. In the mouse splinted excisional wound model, two full-thickness wounds are firstly created on the mouse dorsum, which is followed by application of silicone splint around wounded area. A splinting ring tightly adheres to the skin around full-thickness wound, preventing wound contraction and replicating human processes of re-epithelialization and new tissue formation. The wound is easily accessible for treatment as well as for daily monitoring and quantifying the wound closure.This technique represents valuable approach for the study of wound healing mechanisms and for evaluation of new therapeutic modalities. In this protocol, we describe how to utilize the model to study the effect of gene electrotransfer of plasmid DNA coding for antiangiogenic molecules. Additionally, we also present how to precisely regulate electrical parameters and modify electrode composition to reach optimal therapeutic effectiveness of gene electrotransfer into skin around wounded area.

Partial-Volume Irradiation of Murine Tumors

Radiotherapy is a widely used approach for cancer treatment. However, delivering a single high dose of radiation to bulky tumors can be challenging due to the toxicities induced in the surrounding healthy tissue. To overcome this issue, a nonuniform high dose can be delivered using partial-volume tumor irradiation or spatially fractionated radiotherapy (SFRT). Moreover, SFRT has the potential to induce a stronger antitumor immune response compared to traditional radiotherapy due to the preservation of immune cells in the unirradiated tumor regions. There are several SFRT approaches, including GRID therapy, three-dimensional GRID therapy (LATTICE), microbeam radiation therapy (MRT), and Stereotactic Body Radiation Therapy for PArtial Tumor irradiation targeting exclusively the HYpoxic segment (SBRT-PATHY). The following protocol describes partial-volume tumor irradiation, a technique that enables dose delivery to only a part of the tumor in mice using an X-ray generator and collimators of different dimensions that limit the size of the irradiation field.

Histologic changes of porcine portal vein anastomosis after electrochemotherapy with bleomycin

Electrochemotherapy (ECT1) is used for treatment of unresectable abdominal malignancies. This study aims to show that ECT of porcine portal vein anastomosis is safe and feasible in order to extend the indications for margin attenuation after resection of locally advanced pancreatic carcinoma. No marked differences were found between the control group and ECT treated groups. Electroporation thus caused irreversible damage to the vascular smooth muscle cells in tunica media that could bedue to the narrow irreversible electroporation zone that may occur near the electrodes, or due to vasa vasorum thrombosis in the tunica externa. Based on the absence of vascular complications, and similar histological changes in lienal veinanastomosis, we can conclude that ECT of portal vein anastomosis is safe and feasible.

What We Learned about the Feasibility of Gene Electrotransfer for Vaccination on a Model of COVID-19 Vaccine

DNA vaccination is one of the emerging approaches for a wide range of applications, including prophylactic vaccination against infectious diseases and therapeutic vaccination against cancer. The aim of this study was to evaluate the feasibility of our previously optimized protocols for gene electrotransfer (GET)-mediated delivery of plasmid DNA into skin and muscle tissues on a model of COVID-19 vaccine. Plasmids encoding the SARS-CoV-2 proteins spike (S) and nucleocapsid (N) were used as the antigen source, and a plasmid encoding interleukin 12 (IL-12) was used as an adjuvant. Vaccination was performed in the skin or muscle tissue of C57BL/6J mice on days 0 and 14 (boost). Two weeks after the boost, blood, spleen, and transfected tissues were collected to determine the expression of S, N, IL-12, serum interferon-γ, the induction of antigen-specific IgG antibodies, and cytotoxic T-cells. In accordance with prior in vitro experiments that indicated problems with proper expression of the S protein, vaccination with S did not induce S-specific antibodies, whereas significant induction of N-specific antibodies was detected after vaccination with N. Intramuscular vaccination outperformed skin vaccination and resulted in significant induction of humoral and cell-mediated immunity. Moreover, both boost and adjuvant were found to be redundant for the induction of an immune response. Overall, the study confirmed the feasibility of the GET for DNA vaccination and provided valuable insights into this approach.

Association of Circulating Tumor Cells, Megakaryocytes and a High Immune-Inflammatory Environment in Metastatic Breast Cancer

Liquid biopsy is becoming an important source of new biomarkers during the treatment of metastatic cancer patients. Using size-based microfluid technology, we isolated circulating tumor cells (CTCs) from metastatic breast cancer patients to evaluate their presence and cluster formation, as well as the presence of megakaryocytes and immune-inflammatory blood cells, and to correlate their presence with clinicopathological data and overall survival (OS). In total, 59 patients (median age 60.4 years) were included in the study: 62.7% luminal A/B-like, 20.3% HER2-positive, and 17% triple-negative. Our results showed that at least one CTC was present in 79.7% and ≥5 CTCs in 35.2% of the patients. CTC clusters were present in patients with ≥5 CTCs only (in 19.2% of them), and megakaryocytes were present in 52% of all patients. The presence of CTC clusters and megakaryocytes was positively associated with the CTC count. Patients with low pan-inflammatory value (PIV), low systemic immune-inflammatory index (SII), and low relative change from baseline (ΔPIV%, ΔSII%) were associated with significantly higher OS than their counterparts. ΔPIV%, the presence of infection in the last month, and a long duration of metastatic disease were identified as independent prognostic factors for OS. The interplay of CTCs, CTC clusters, megakaryocytes, and PIV needs to be further explored.

HPV-positive murine oral squamous cell carcinoma: development and characterization of a new mouse tumor model for immunological studies

BACKGROUND

Infection with high-risk human papillomavirus (HPV) strains is one of the risk factors for the development of oral squamous cell carcinoma (OSCC). Some patients with HPV-positive OSCC have a better prognosis and respond better to various treatment modalities, including radiotherapy or immunotherapy. However, since HPV can only infect human cells, there are only a few immunocompetent mouse models available that enable immunological studies. Therefore, the aim of our study was to develop a transplantable immunocompetent mouse model of HPV-positive OSCC and characterize it in vitro and in vivo.

METHODS

Two monoclonal HPV-positive OSCC mouse cell lines were established by inducing the expression of HPV-16 oncogenes E6 and E7 in the MOC1 OSCC cell line using retroviral transduction. After confirming stable expression of HPV-16 E6 and E7 with quantitative real-time PCR and immunofluorescence staining, the cell lines were further characterized in vitro using proliferation assay, wound healing assay, clonogenic assay and RNA sequencing. In addition, tumor models were characterized in vivo in C57Bl/6NCrl mice in terms of their histological properties, tumor growth kinetics, and radiosensitivity. Furthermore, immunofluorescence staining of blood vessels, hypoxic areas, proliferating cells and immune cells was performed to characterize the tumor microenvironment of all three tumor models.

RESULTS

Characterization of the resulting MOC1-HPV cell lines and tumor models confirmed stable expression of HPV-16 oncogenes and differences in cell morphology, in vitro migration capacity, and tumor microenvironment characteristics. Although the cell lines did not differ in their intrinsic radiosensitivity, one of the HPV-positive tumor models, MOC1-HPV K1, showed a significantly longer growth delay after irradiation with a single dose of 15 Gy compared to parental MOC1 tumors. Consistent with this, MOC1-HPV K1 tumors had a lower percentage of hypoxic tumor area and a higher percentage of proliferating cells. Characteristics of the newly developed HPV-positive OSCC tumor models correlate with the transcriptomic profile of MOC1-HPV cell lines.

CONCLUSIONS

In conclusion, we developed and characterized a novel immunocompetent mouse model of HPV-positive OSCC that exhibits increased radiosensitivity and enables studies of immune-based treatment approaches in HPV-positive OSCC.

Effects of Electrochemotherapy on Immunologically Important Modifications in Tumor Cells

Electrochemotherapy (ECT) is a clinically acknowledged method that combines the use of anticancer drugs and electrical pulses. Electrochemotherapy with bleomycin (BLM) can induce immunogenic cell death (ICD) in certain settings. However, whether this is ubiquitous over different cancer types and for other clinically relevant chemotherapeutics used with electrochemotherapy is unknown. Here, we evaluated in vitro in the B16-F10, 4T1 and CT26 murine tumor cell lines, the electrochemotherapy triggered changes in the ICD-associated damage-associated molecular patterns (DAMPs): Calreticulin (CRT), ATP, High Mobility Group Box 1 (HMGB1), and four immunologically important cellular markers: MHCI, MHC II, PD-L1 and CD40. The changes in these markers were investigated in time up to 48 h after ECT. We showed that electrochemotherapy with all three tested chemotherapeutics induced ICD-associated DAMPs, but the induced DAMP signature was cell line and chemotherapeutic concentration specific. Similarly, electrochemotherapy with CDDP, OXA or BLM modified the expression of MHC I, MHC II, PD-L1 and CD40. The potential of electrochemotherapy to change their expression was also cell line and chemotherapeutic concentration specific. Our results thus put the electrochemotherapy with clinically relevant chemotherapeutics CDDP, OXA and BLM on the map of ICD inducing therapies.

Targeting Non-Coding RNAs for the Development of Novel Hepatocellular Carcinoma Therapeutic Approaches

Hepatocellular carcinoma (HCC) remains a global health challenge, representing the third leading cause of cancer deaths worldwide. Although therapeutic advances have been made in the few last years, the prognosis remains poor. Thus, there is a dire need to develop novel therapeutic strategies. In this regard, two approaches can be considered: (1) the identification of tumor-targeted delivery systems and (2) the targeting of molecule(s) whose aberrant expression is confined to tumor cells. In this work, we focused on the second approach. Among the different kinds of possible target molecules, we discuss the potential therapeutic value of targeting non-coding RNAs (ncRNAs), which include micro interfering RNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs). These molecules represent the most significant RNA transcripts in cells and can regulate many HCC features, including proliferation, apoptosis, invasion and metastasis. In the first part of the review, the main characteristics of HCC and ncRNAs are described. The involvement of ncRNAs in HCC is then presented over five sections: (a) miRNAs, (b) lncRNAs, (c) circRNAs, (d) ncRNAs and drug resistance and (e) ncRNAs and liver fibrosis. Overall, this work provides the reader with the most recent state-of-the-art approaches in this field, highlighting key trends and opportunities for more advanced and efficacious HCC treatments.

Treatment of vulvar cancer recurrences with electrochemotherapy - a detailed analysis of possible causes for unsuccessful treatment

BACKGROUND

Electrochemotherapy has good local effectiveness in the treatment of vulvar cancer. Most studies have reported the safety and effectiveness of electrochemotherapy for palliative treatment of gynecological cancers and mostly vulvar squamous cell carcinoma. Some tumors, however, fail to respond to electrochemotherapy. The biological features/determinants for the nonresponsiveness are not determined yet.

PATIENT AND METHODS

A recurrence of vulvar squamous cell carcinoma was treated by electrochemotherapy using intravenous administration of bleomycin. The treatment was performed by hexagonal electrodes according to standard operating procedures. We analyzed the factors that could determine nonresponsiveness to electrochemotherapy.

RESULTS

Based on the presented case of nonresponsive vulvar recurrence to electrochemotherapy, we hypothesize that the vasculature of the tumors prior to treatment may predict the response to electrochemotherapy. The histological analysis showed minimal presence of blood vessels in the tumor. Thus, low perfusion may reduce drug delivery and lead to a lower response rate because of the minor antitumor effectiveness of vascular disruption. In this case, no immune response in the tumor was elicited by electrochemotherapy.

CONCLUSIONS

In this case, of nonresponsive vulvar recurrence treated by electrochemotherapy, we analyzed possible factors that could predict treatment failure. Based on histological analysis, low vascularization of the tumor was observed, which hampered drug delivery and distribution and resulted in no vascular disrupting action of electro-chemotherapy. All these factors could contribute to ineffective treatment with electrochemotherapy.

Comparison of DNA sensing by non-immune cells and tissues

Pattern recognition receptors (PRRs) are nearly ubiquitous in both immune and non-immune mammalian cells. PRRs detect pathogen invasion as well as internal damage, inducing the secretion of pro-inflammatory molecules and cell death. Members of the PRR subset that detect intracellular DNA are termed DNA sensors. We examined DNA sensing in non-immune cells and their equivalent tissues using electroporation. This physical delivery method mitigates the need for viral or chemical agents that could confound the source of PRR activation. We used RT-qPCR and/or RNA-Seq to quantify mRNAs encoding DNA sensors and their signaling pathways and western blots, ELISAs and bead arrays to quantify related proteins. Several tumor cell types and non-tumor cells, including keratinocytes, fibroblasts, and myoblasts, expressed different DNA sensors at baseline and responded to backbone plasmid DNA delivery with individual DNA sensor signatures. Some similarities were observed among all these cell types, including upregulation of the DNA sensors ZBP1, DDX60, and Ifi204, the mouse analog of human Ifi16. Each cell type secreted a range of pro-inflammatory molecules including Type I interferon. DNA electroporation to B16-F10 melanomas, skin, and skeletal muscle induced unique cytokine and chemokine signatures, paralleling cellular signatures. ZBP1, DDX60, and Ifi204 were upregulated in skin and muscle; however, no significant regulation was observed in tumors. In muscle particularly, this may be due to the homogeneity of the tissue; tumors are inherently heterogeneous, producing an assortment of individual cellular responses.

Supported by NIH grant R01CA196796.

Sunitinib potentiates the cytotoxic effect of electrochemotherapy in pancreatic carcinoma cells

BACKGROUND

One of the new treatment options for unresectable locally advanced pancreatic cancer is electrochemotherapy (ECT), a local ablative therapy that potentiates the entry of chemotherapeutic drugs into the cells, by the application of an electric field to the tumor. Its feasibility and safety were demonstrated in preclinical and clinical studies; however, there is a lack of preclinical studies assessing the actions of different drugs used in ECT, their mechanisms and interactions with other target drugs that are used in clinical practice.

MATERIALS AND METHODS

The aim of the study was to determine the cytotoxicity of two chemotherapeutic drugs usually used in ECT (bleomycin and cisplatin) in the BxPC-3 human pancreatic carcinoma cell line and evaluate the interactions of ECT with the targeted drug sunitinib. First, the cytotoxicity of ECT using both chemotherapeutics was determined. In the next part, the interactions of ECT and sunitinib were evaluated through determination of combined cytotoxicity, sunitinib targets and kinetics of cell death.

RESULTS

The results demonstrate that ECT is effective in pancreatic cancer cell line, especially when bleomycin is used, with the onset of cell death in the first hours after the treatment, reaching a plateau at 20 hours after the treatment. Furthermore, we provide the rationale for combining ECT with bleomycin and the targeted drug sunitinib to potentiate cytotoxicity. The combined treatment of sunitinib and ECT was synergistic for bleomycin only at the highest used concentration of bleomycin 0.14 μM, whereas with lower doses of bleomycin, this effect was not observed. The interaction of ECT and treatment with sunitinib was confirmed by course of the cell death, also indicating on synergism.

CONCLUSIONS

ECT and sunitinib combined treatment has clinical potential, and further studies are warranted.

Electrochemotherapy as an Alternative Treatment Option to Pelvic Exenteration for Recurrent Vulvar Cancer of the Perineum Region

Objective: Pelvic exenteration in women with recurrent vulvar carcinoma is associated with high morbidity and mortality and substantial treatment costs. Because pelvic exenteration severely affects the quality of life and can lead to significant complications, other treatment modalities, such as electrochemotherapy, have been proposed. The aim of this study was to evaluate the feasibility and suitability of electrochemotherapy in the treatment of recurrent vulvar cancer. We aimed to analyze the treatment options, treatment outcomes, and complications in patients with recurrent vulvar cancer of the perineum. Methods: A retrospective analysis of patients who had undergone pelvic exenteration for vulvar cancer at the Institute of Oncology Ljubljana over a 16-year period was performed. As an experimental, less mutilating treatment, electrochemotherapy was performed on one patient with recurrent vulvar cancer involving the perineum. Comparative data analysis was performed between the group with pelvic exenteration and the patient with electrochemotherapy, comparing hospital stay, disease recurrence after treatment, survival after treatment in months, and quality of life after treatment. Results: We observed recurrence of disease in 2 patients with initial FIGO stage IIIC disease 3 months and 32 months after pelvic exenteration, and they died of the disease 15 and 38 months after pelvic exenteration. Two patients with FIGO stage IB were alive at 74 and 88 months after pelvic exenteration. One patient with initial FIGO stage IIIC was alive 12 months after treatment with electrochemotherapy with no visible signs of disease progression in the vulvar region, and the lesions had a complete response. The patient treated with electrochemotherapy was hospitalized for 4 days compared with the patients with pelvic exenteration, in whom the average hospital stay was 19.75 (± 1.68) days. Conclusion: Our experience has shown that electrochemotherapy might be a less radical alternative to pelvic exenteration, especially for patients with initially higher FIGO stages.

Non-Clinical In Vitro Evaluation of Antibiotic Resistance Gene-Free Plasmids Encoding Human or Murine IL-12 Intended for First-in-Human Clinical Study

Interleukin 12 (IL-12) is a key cytokine that mediates antitumor activity of immune cells. To fulfill its clinical potential, the development is focused on localized delivery systems, such as gene electrotransfer, which can provide localized delivery of IL-12 to the tumor microenvironment. Gene electrotransfer of the plasmid encoding human IL-12 is already in clinical trials in USA, demonstrating positive results in the treatment of melanoma patients. To comply with EU regulatory requirements for clinical application, which recommend the use of antibiotic resistance gene-free plasmids, we constructed and developed the production process for the clinical grade quality antibiotic resistance gene-free plasmid encoding human IL-12 (p21-hIL-12-ORT) and its ortholog encoding murine IL-12 (p21-mIL-12-ORT). To demonstrate the suitability of the p21-hIL-12-ORT or p21-mIL-12-ORT plasmid for the first-in-human clinical trial, the biological activity of the expressed transgene, its level of expression and plasmid copy number were determined in vitro in the human squamous cell carcinoma cell line FaDu and the murine colon carcinoma cell line CT26. The results of the non-clinical evaluation in vitro set the basis for further in vivo testing and evaluation of antitumor activity of therapeutic molecules in murine models as well as provide crucial data for further clinical trials of the constructed antibiotic resistance gene-free plasmid in humans.

Abstract PO-013: Irradiation induced expression of cytosolic DNA sensors and cytokines is associated with HPV status of pharyngeal squamous cell carcinoma cells

Human papillomavirus (HPV) positive pharyngeal squamous cell carcinoma (PSCC) appears to differ from HPV negative PSCC regarding several different characteristics due to the expression of HPV viral oncoproteins E6 and E7. Clinical studies suggest that HPV positive PSCC are more radiosensitive than HPV negative ones, however the exact mechanisms are still not known. It was previously shown that after X-ray radiation DNA accumulates in the cytosol of survived cells and can be sensed by specific pattern recognition receptors, i.e. cytosolic DNA sensors, which can modulate immune response and thus radiosensitivity of tumors. Therefore, the aim of our study was first to investigate the radiosensitivity and involvement of DNA sensing pathways in response to radiation in HPV positive and HPV negative PSCC in vitro. For determination of the radiosensitivity, HPV negative (FaDu and UM-SCC-6) and HPV positive (2A3 and UPCI:SCC090) PSCC cell lines were plated in 96 well plates and irradiated with different single doses (0, 2, 4, 6, 8 and 10 Gy). After 4 cell’s division PrestoBlue™ Cell Viability Reagent was used to determine the survival of cells taking into account different growth rate of the cells. For determination of DNA sensors and cytokines mRNA levels, PSCC cell lines were plated and irradiated with different single doses (0, 4 and 8 Gy). After 24 and 48 hours RNA was isolated using peqGOLD Total RNA Kit (VWR, West Chester, PA, USA) and reverse transcribed into cDNA using the SuperScript VILO cDNA Synthesis Kit (Invitrogen, Thermo Fisher Scientific). qRT-PCR was used to determine viral load (expression of HPV oncoproteins E6 and E7 mRNAs), expression of DNA sensors (cGAS, STING, RIG-I, DAI, IFI16, DDX60) and cytokines (IFNb, TNFa, IL1b). The expression of cytosolic DNA sensors and cytokines was dose- and time-dependent in both types of cells. The expression of DNA sensors DAI and RIG-I after irradiation was upregulated in HPV negative cell lines but not in HPV positive ones. The expression of cytokines IFN β and IL 1B was also upregulated only in HPV negative cell lines. Between the two HPV negative cell lines FaDu and SCC6, the expression profile did not differ, while the expression of DNA sensors and cytokines was higher in HPV positive cell line 2A3 compared to UM-SCC-6 cell lines, which has a higher level of viral proteins E6 and E7. In conclusion, our results indicate that on the in vitro level, DNA sensors are differentially expressed in response to irradiation in PSCC cell lines based on HPV infection but does not affect the radiosensitivity of the cells. Further in vivo studies are needed to elucidate the involvement of immune system in the response.

Citation Format: Kristina Levpuscek, Tanja Jesenko, Primoz Strojan, Gregor Sersa, Maja Cemazar. Irradiation induced expression of cytosolic DNA sensors and cytokines is associated with HPV status of pharyngeal squamous cell carcinoma cells [abstract]. In: Proceedings of the AACR Virtual Special Conference on Radiation Science and Medicine; 2021 Mar 2-3. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(8_Suppl):Abstract nr PO-013.

Challenges in Combining Immunotherapy with Radiotherapy in Recurrent/Metastatic Head and Neck Cancer

Immunotherapy with immune checkpoint inhibitors (ICI) has recently become a standard part of the treatment of recurrent or metastatic head and neck squamous cell carcinoma (R/M HNSCC), although the response rates are low. Numerous preclinical and clinical studies have now illuminated several mechanisms by which radiotherapy (RT) enhances the effect of ICI. From RT-induced immunogenic cancer cell death to its effect on the tumor microenvironment and vasculature, the involved mechanisms are diverse and intertwined. Moreover, the research of these interactions is challenging because of the thin line between immunostimulatory and the immunosuppressive effect of RT. In the era of active research of immunoradiotherapy combinations, the significance of treatment and host-related factors that were previously seen as being less important is being revealed. The impact of dose and fractionation of RT is now well established, whereas selection of the number and location of the lesions to be irradiated in a multi-metastatic setting is something that is only now beginning to be understood. In addition to spatial factors, the timing of irradiation is as equally important and is heavily dependent on the type of ICI used. Interestingly, using smaller-than-conventional RT fields or even partial tumor volume RT could be beneficial in this setting. Among host-related factors, the role of the microbiome on immunotherapy efficacy must not be overlooked nor can we neglect the role of gut irradiation in a combined RT and ICI setting. In this review we elaborate on synergistic mechanisms of immunoradiotherapy combinations, in addition to important factors to consider in future immunoradiotherapy trial designs in R/M HNSCC.

Preclinical and Clinical Evaluation of Magnetic-Activated Cell Separation Technology for CTC Isolation in Breast Cancer

Circulating tumor cell (CTC) count is an independent prognostic factor in early breast cancer. CTCs can be found in the blood of 20% of patients prior to neoadjuvant therapy. We aimed to assess the suitability of magnetic-activated cell separation (MACS) technology for isolation and cytological characterization of CTCs. In the preclinical part of the study, cell lines were spiked into buffy coat samples derived from healthy donors, and isolated using MACS. Breast cancer cells with preserved cell morphology were successfully isolated. In the clinical part, blood for CTC isolation was drawn from 44 patients with early and locally advanced breast cancer prior to neoadjuvant chemotherapy. Standard Giemsa, Papanicolaou and pancytokeratin staining was applied. 2.3% of samples contained cells that meet both the morphological and immunocytochemical criteria for CTC. In 32.6% of samples, partially degenerated pancytokeratin negative cells with morphological features of tumor cells were observed. In 65.1% of samples, CTCs were not found. In conclusion, our results demonstrate that morphologically intact tumor cells can be isolated using MACS technology. However, morphologically intact tumor cells were not detected in the clinical part of the study. At present, MACS technology does not appear suitable for use in a clinical cytopathology laboratory.

Multiparametric High-Resolution MRI as a Tool for Mapping of Hypoxic Level in Tumors

Hypoxia is a condition, common to most malignant tumors, where oxygen tension in the tissue is below the physiological level. Among consequences of tumor hypoxia is also altered cancer cell metabolism that contributes to cancer therapy resistance. Therefore, precise assessment of tumor hypoxia is important for monitoring the tumor treatment progression. In this study, we propose a simple model for prediction of hypoxic level in tumors based on multiparametric magnetic resonance imaging. The study was performed on B16F1 murine melanoma tumors ex vivo that were first magnetic resonance scanned and then analyzed for hypoxic level using hypoxia-inducable factor 1-alpha antibody staining. Each tumor was analyzed in identical sections and in identical regions of interest for pairs of hypoxic level and magnetic resonance values (apparent diffusion coefficient and T₂). This was followed by correlation analysis between hypoxic level and respective magnetic resonance values. A moderate correlation was found between hypoxic level and apparent diffusion coefficient (ρ = 0.56, P < .00001) and lower between hypoxic level and T₂ (ρ = 0.38, P < .00001). The data were analyzed further to obtain simple predictive models based on the multiple linear regression analysis of the measured hypoxic level (dependent variable) and apparent diffusion coefficient and T₂ (independent variables). Among the hypoxic level models, the most efficient was the 3-parameter model given by relation (HL = k_ADCADC + k_T2T₂ + b), where k_ADC = 26%/µm²/ms, k_T2 = 0.8%/ms, and b = −32%. The model can be used for calculation of the predicted hypoxic level map based on magnetic resonance–measured apparent diffusion coefficient and T₂ maps. Similar prediction models, based on tumor apparent diffusion coefficient and T₂ maps, can be done also for other tumor types in vivo and can therefore help in assessment of tumor treatment as well as to better understand the role of hypoxia in cancer progression.

Upregulation of DNA Sensors in B16.F10 Melanoma Spheroid Cells After Electrotransfer of pDNA

Increased expression of cytosolic DNA sensors, a category of pattern recognition receptor, after control plasmid DNA electrotransfer was observed in our previous studies on B16.F10 murine melanoma cells. This expression was correlated with the upregulation of proinflammatory cytokines and chemokines and was associated with cell death. Here, we expanded our research to include the influence of features of cells in a 3-dimensional environment, which better represents the tumors' organization in vivo. Our results show that lower number of cells were transfected in spheroids compared to 2-dimensional cultures, that growth was delayed after electroporation alone or after electrotransfer of plasmid DNA, and that DNA sensors DDX60, DAI/ZBP1, and p204 were upregulated 4 hours and 24 hours after electrotransfer of plasmid DNA. Moreover, the cytokines interferon β and tumor necrosis factor α were also upregulated but only 4 hours after electrotransfer of plasmid DNA. Thus, our results confirm the results obtained in 2-dimensional cell cultures demonstrating that electrotransfer of plasmid DNA to tumor cells in spheroids also upregulated cytosolic DNA sensors and cytokines.

Increased permeability of blood vessels after reversible electroporation is facilitated by alterations in endothelial cell-to-cell junctions

Delivery of electric field pulses, i.e. electroporation (EP), to tissues has been shown to have a blood flow modifying effect. Indeed, the diameter of blood vessels exposed to EP is immediately reduced resulting in blood flow abrogation, followed by an increase in vascular permeability. The main cause of the increased permeability remains unknown. The aim of this study was to determine whether the in vivo effects of EP on permeability of blood vessels are linked to the permeabilization of endothelial cells' membrane (EC) and/or disruption of cell-to-cell junctions. We used a dorsal window chamber model in C57Bl/6 mice coupled with multiphoton microscopy and fluorescently labelled antibodies against PECAM-1 (CD31) to visualize endothelial cell-to-cell junctions. Clinically validated EP parameters were used and behavior of cell-to-cell junctions, in combination with leakage of 70 kDa fluorescein isothiocyanate labelled dextran (FD), was followed in time. After EP, a constriction of blood vessels was observed and correlated with the change in the shape of ECs. This was followed by an increase in permeability of blood vessels for 70 kDa FD and a decrease in the volume of labelled cell-to-cell junctions. Both parameters returned to pre-treatment values in 50% of mice. For the remaining 50%, we hypothesize that disruption of cell-to-cell junctions after EP may trigger the platelet activation cascade. Our findings show for the first time in vivo that alterations in cell-to-cell junctions play an important role in the response of blood vessels to EP and explain their efficient permeabilization.