Development of GPC3-CAR-NK cells and optimization as a therapy for HCC.

Hepatocellular carcinoma (HCC) is a highly malignant tumor characterized by insidious onset and rapid progression, with limited treatment choices. One treatment modality, chimeric antigen receptor (CAR)-modified natural killer (NK) cell immunotherapy, has shown promise for various cancers. In this study, we developed two GPC3-specific CAR-NK-92 cell lines (GPC3-CAR-NK) and explored their antitumor efficacy for the treatment of HCC. Significant levels of cytokine production and in vitro cytotoxicity were produced following co-culture of GPC3+ HCC cells with the developed GPC3-CAR-NK cells. GC33-G2D-NK cells with NK cell-specific signaling domains showed better activation and killing abilities than GC33-CD28-NK cells containing T cell-specific signaling domains. Moreover, GC33-G2D-NK cells efficiently eliminated tumors in cell-derived xenograft and patient-derived xenograft mouse models. In an abdominal metastasis model, intraperitoneally delivered GC33-G2D-NK cells showed better antitumor ability than intravenously injected cells. Finally, the combination of microwave ablation with GC33-G2D-NK cell administration showed greater CAR-NK infiltration and tumor regression in ablated tumors than monotherapy alone. These findings indicate that administration of GPC3-CAR-NK cells may be a potential strategy for the treatment of HCC, and regional delivery or their combination with microwave ablation may optimize their efficacy against HCC and may have translational value.

NK-92MI Cells Engineered with Anti-claudin-6 Chimeric Antigen Receptors in Immunotherapy for Ovarian Cancer.

Background: The application of chimeric antigen receptor (CAR) NK cells in solid tumors is hindered by lack of tumor-specific targets and inefficient CAR-NK cell efficacy. Claudin-6 (CLDN6) has been reported to be overexpressed in ovarian cancer and may be an attractive target for CAR-NK cells immunotherapy. However, the feasibility of using anti-CLDN6 CAR-NK cells to treat ovarian cancer remains to be explored. Methods: CLDN6 expression in primary human ovarian cancer, normal tissues and cell lines were detected by immunohistochemistry and western blot. Two types of third-generation CAR NK-92MI cells targeting CLDN6, CLDN6-CAR1 NK-92MI cells with domains containing self-activated elements (NKG2D, 2B4) and CLDN6-CAR2 NK-92MI cells with classical domains (CD28, 4-1BB) were constructed by lentivirus transfection, sorted by flow cytometry and verified by western blot and qPCR. OVCAR-3, SK-OV-3, A2780, Hey and PC-3 cells expressing the GFP and luciferase genes were transduced. Subcutaneous and intraperitoneal tumor models were established via NSG mice. The ability of CLDN6-CAR NK cells to kill CLDN6-positive ovarian cancer cells were evaluated in vitro and in vivo by live cell imaging and bioluminescence imaging. Results: Both CLDN6-CAR1 and CLDN6-CAR2 NK-92MI cells could specifically killed CLDN6-positive ovarian cancer cells (OVCAR-3, SK-OV-3, A2780 and Hey), rather than CLDN6 negative cell (PC-3), in vitro. CLDN6-CAR1 NK-92MI cells with domains containing self-activated elements (NKG2D, 2B4) exhibited stronger cytotoxicity than CLDN6-CAR2 NK-92MI cells with classical domains (CD28, 4-1BB). Furthermore, CLDN6-CAR1 NK cells could effectively eliminate ovarian cancer cells in subcutaneous and intraperitoneal tumor models. More importantly, CAR-NK cells combined with immune checkpoint inhibitors, anti-PD-L1, could synergistically enhance the antitumor efficacy of CLDN6-targeted CAR-NK cells. Conclusions: These results indicate that CLDN6-CAR NK cells possess strong antitumor activity and represent a promising immunotherapeutic modality for ovarian cancer.

Lenvatinib, sintilimab plus transarterial chemoembolization for advanced stage hepatocellular carcinoma: A phase II study.

BACKGROUND & AIMS: Our retrospective study has suggested encouraging outcomes of lenvatinib combined with PD-1 inhibitor and transarterial chemoembolization (TACE) on advanced hepatocellular carcinoma (HCC). This phase II trial was conducted to prospectively investigate the efficacy and safety of lenvatinib, sintilimab (a PD-1 inhibitor) plus TACE (Len-Sin-TACE) in patients with advanced stage HCC. METHODS: This was a single-arm phase II trial. Patients with BCLC stage C HCC were recruited. They received lenvatinib (bodyweight ≥60 kg, 12 mg; bodyweight <60 kg, 8 mg) orally once daily, sintilimab (200 mg) intravenously once every 3 weeks, and on demand TACE. The primary endpoint was progression-free survival (PFS) per mRECIST. RESULTS: Thirty patients were enrolled. The primary endpoint was met with a median PFS of 8.0 (95% confidence interval [CI]: 6.1-9.8) months per mRECIST, which was the same as that per RECIST 1.1. The objective response rate was 60.0% per mRECIST and 30.0% per RECIST 1.1. The disease control rate was 86.7% per mRECIST/RECIST 1.1. The median duration of response was 7.4 (95% CI: 6.6-8.2) months per mRECIST (n = 18) and 4.3 (95% CI: 4.0-4.6) months per RECIST 1.1 (n = 9). The median overall survival was 18.4 (95% CI: 14.5-22.3) months. Treatment-related adverse events (TRAEs) occurred in 28 patients (93.3%) and grade 3 TRAEs were observed in 12 patients (40.0%). There were no grade 4/5 TRAEs. CONCLUSIONS: Len-Sin-TACE showed promising antitumour activities with a manageable safety profile in patients with advanced stage HCC. The preliminary results need to be further evaluated with phase III randomized trials.

Tyrosine-kinase inhibitor combined with iodine-125 seed brachytherapy for hepatocellular carcinoma refractory to transarterial chemoembolization: a propensity-matched study.

PURPOSE: To investigate the efficacy and safety of tyrosine-kinase inhibitor (TKI) combined with iodine-125 seed brachytherapy (TKI-I) versus TKI alone for patients with hepatocellular carcinoma (HCC) refractory to transarterial chemoembolization (TACE). METHODS: Data of patients with TACE-refractory HCC who received TKI (sorafenib or lenvatinib) or TKI-I from September 2018 to December 2020 were retrospectively analyzed. A propensity score matching (PSM) was performed to diminish potential bias. The primary endpoints were overall survival (OS) and time to progression (TTP). Tumor responses and treatment-related adverse events (TRAEs) were also compared between the two groups. RESULTS: A total of 132 patients were included in this study. Under PSM, 48 paired patients were selected for comparison. The median OS was 23.2 (95% CI 20.9-25.1) months in the TKI-I group versus 13.9 (95% CI 11.1-16.7) months in the TKI group (P < 0.001). The median TTP was 12.8 (95% CI 10.1-15.5) months in the TKI-I group versus 5.8 (95% CI 5.0-6.6) months in the TKI group (P < 0.001). Patients in the TKI-I group had higher objective response rate (68.8% vs. 33.3%, P = 0.001) and disease control rate (89.6% vs. 66.7%, P = 0.007) than those in the TKI group. The incidence and severity of TRAEs in the TKI-I group were comparable to those in the TKI group (any grade, 89.7% vs. 92.2%, P = 0.620; ≥grade 3, 33.8% vs. 32.8%, P = 0.902). CONCLUSIONS: TKI-I was safe and significantly improved survival over TKI alone in HCC patients with TACE refractoriness.

Remodelling of tumour microenvironment by microwave ablation potentiates immunotherapy of AXL-specific CAR T cells against non-small cell lung cancer.

The complex immunosuppressive tumour microenvironment (TME) and lack of tumour-specific targets hinder the application of chimeric antigen receptor (CAR) T cells in the treatment of solid tumours. Combining local treatment with CAR T cell immunotherapy may regulate the TME and enhance the killing potency of CAR T cells in solid tumours. Here, we show that AXL, which is highly expressed in non-small cell lung cancer (NSCLC) but not in normal tissues, might be a target for CAR T cell therapy. AXL-CAR T cells alone cause moderate tumour regression in subcutaneous and pulmonary metastatic lung cancer cell-derived xenograft models. Combination of microwave ablation (MWA) and AXL-CAR T cells have superior antitumour efficacy. MWA enhances the activation, infiltration, persistence and tumour suppressive properties of AXL-CAR T cells in AXL-positive NSCLC patient-derived xenograft tumours via TME remodelling. The combination therapy increases the mitochondrial oxidative metabolism of tumour-infiltrating CAR T cells. Combination treatment induces significant tumour suppression without observed toxicities in humanized immunocompetent mice. The synergistic therapeutic effect of MWA and AXL-CAR T cells may be valuable for NSCLC treatment.

Transarterial Chemoembolization Combined With Lenvatinib Plus PD-1 Inhibitor for Advanced Hepatocellular Carcinoma: A Retrospective Cohort Study.

Purpose: To investigate the efficacy and safety of transarterial chemoembolization (TACE) combined with lenvatinib plus PD-1 inhibitor (TACE-L-P) versus TACE combined with lenvatinib (TACE-L) for patients with advanced hepatocellular carcinoma (HCC). Materials and Methods: Data of advanced HCC patients treated with TACE-L-P (TACE-L-P group) or TACE-L (TACE-L group) from January 2019 to December 2020 were prospectively collected and retrospectively analyzed. The differences in overall survival (OS), progression-free survival (PFS), tumor responses (based on modified Response Evaluation Criteria in Solid Tumors) and adverse events (AEs) were compared between the two groups. Potential factors affecting OS and PFS were determined. Results: A total of 81 patients were included in this study. Among them, 41 received TACE-L-P and 40 received TACE-L. The patients in TACE-L-P group had prolonged OS (median, 16.9 vs. 12.1 months, P=0.009), longer PFS (median, 7.3 vs. 4.0 months, P=0.002) and higher objective response rate (56.1% vs. 32.5%, P=0.033) and disease control rate (85.4% vs. 62.5%, P=0.019) than those in TACE-L group. Multivariate analyses revealed that the treatment option of TACE-L, main portal vein invasion and extrahepatic metastasis were the independent risk factors for OS, while TACE-L and extrahepatic metastasis were the independent risk factors for PFS. In subgroup analyses, a superior survival benefit was achieved with TACE-L-P in patients with extrahepatic metastasis or tumor number >3 but not in those with main portal vein invasion. The incidence and severity of AEs in TACE-L-P group were comparable to those in TACE-L group (any grade, 92.7% vs. 95.0%, P=1.000; grade 3, 36.6% vs. 32.5%, P=0.699). Conclusion: TACE-L-P significantly improved survival over TACE-L with an acceptable safety profile in advanced HCC patients, especially those with extrahepatic metastasis or tumor number >3 but without main portal vein invasion.

CAR NK-92 cells targeting DLL3 kill effectively small cell lung cancer cells in vitro and in vivo.

Small cell lung cancer (SCLC) is characterized by a high relapse rate, drug tolerance, and limited treatment choices. Chimeric antigen receptor (CAR)-modified NK cells represent a promising immunotherapeutic modality for cancer treatment. However, their potential applications have not been explored in SCLC. Delta-like ligand 3 (DLL3) has been reported to be overexpressed in SCLC and may be a rational target for CAR NK immunotherapy. In this study, we developed DLL3-specific NK-92 cells and explored their potential in the treatment of SCLC. A coculture of DLL3+ SCLC cell lines with DLL3-CAR NK-92 cells exhibited significant in vitro cytotoxicity and cytokine production. DLL3-CAR NK-92 cells induced tumor regression in an H446-derived pulmonary metastasis tumor model under a good safety threshold. The potent antitumor activities of DLL3-CAR NK-92 cells were observed in subcutaneous tumor models of SCLC. Moreover, obvious tumor-infiltrated DLL3-CAR NK-92 cells were detected in DLL3+ SCLC xenografts. These findings indicate that DLL3-CAR NK-92 cells might be a potential strategy for the treatment of SCLC.

Development of mesothelin-specific CAR NK-92 cells for the treatment of gastric cancer.

Background: The application of chimeric antigen receptor (CAR) NK cells in solid tumors is hindered by lack of tumor-specific targets and inefficient CAR NK cell efficacy. It has been reported that mesothelin (MSLN) may be an ideal immunotherapy target for gastric cancer. However, the feasibility of using anti-MSLN CAR NK cells to treat gastric cancer remains to be studied. Methods: MSLN expression in primary human gastric cancer, normal tissues and cell lines were detected. MSLN and CD19 targeted CAR NK-92 (MSLN- and CD19-CAR NK) cells were constructed, purified and verified. N87, MKN-28, AGS and Huh-7 cells expressing the GFP and luciferase genes were transduced. Cell- and patient-derived xenograft (PDX) were established via NSG mice. The ability of MSLN-CAR NK cells to kill MSLN-positive gastric cancer cells were evaluated in vitro and in vivo. Results: MSLN-CAR NK cells can specifically kill MSLN-positive gastric cancer cells (N87, MKN-28 and AGS), rather than MSLN negative cell (Huh-7), in vitro. Moreover, compared with parental NK-92 cells and CD19-CAR NK cells, stronger cytokine secretions were secreted in MSLN-CAR NK cells cocultured with N87, MKN-28 and AGS. Furthermore, MSLN-CAR NK cells can effectively eliminate gastric cancer cells in both subcutaneous and intraperitoneal tumor models. They could also significantly prolong the survival of intraperitoneally tumor-bearing mice. More importantly, the potent antitumor effect and considerable NK cell infiltration were observed in the patient-derived xenograft treated with MSLN-CAR NK cells, which further warranted the therapeutic effects of MSLN-CAR NK cells to treat gastric cancer. Conclusion: These results demonstrate that MSLN-CAR NK cells possess strong antitumor activity and represent a promising therapeutic approach to gastric cancer.

IL-7 and CCL19-secreting CAR-T cell therapy for tumors with positive glypican-3 or mesothelin.

Although chimeric antigen receptor (CAR)-engineered T cells have shown great success in the treatment of B cell malignancies, this strategy has limited efficacy in patients with solid tumors. In mouse CAR-T cells, IL-7 and CCL19 expression have been demonstrated to improve T cell infiltration and CAR-T cell survival in mouse tumors. Therefore, in the current study, we engineered human CAR-T cells to secrete human IL-7 and CCL19 (7 × 19) and found that these 7 × 19 CAR-T cells showed enhanced capacities of expansion and migration in vitro. Furthermore, 7 × 19 CAR-T cells showed superior tumor suppression ability compared to conventional CAR-T cells in xenografts of hepatocellular carcinoma (HCC) cell lines, primary HCC tissue samples and pancreatic carcinoma (PC) cell lines. We then initiated a phase 1 clinical trial in advanced HCC/PC/ovarian carcinoma (OC) patients with glypican-3 (GPC3) or mesothelin (MSLN) expression. In a patient with advanced HCC, anti-GPC3-7 × 19 CAR-T treatment resulted in complete tumor disappearance 30 days post intratumor injection. In a patient with advanced PC, anti-MSLN-7 × 19 CAR-T treatment resulted in almost complete tumor disappearance 240 days post-intravenous infusion. Our results demonstrated that the incorporation of 7 × 19 into CAR-T cells significantly enhanced the antitumor activity against human solid tumor. Trial registration: NCT03198546. Registered 26 June 2017, https://clinicaltrials.gov/ct2/show/NCT03198546?term=NCT03198546&draw=2&rank=1.

Induction of ferroptosis in human nasopharyngeal cancer cells by cucurbitacin B: molecular mechanism and therapeutic potential.

Cucurbitacin B (CuB) is a widely available triterpenoid molecule that exhibits various biological activities. Previous studies on the anti-tumour mechanism of CuB have mostly focused on cell apoptosis, and research on the ferroptosis-inducing effect has rarely been reported. Herein, we first discovered the excellent cytotoxicity of CuB towards human nasopharyngeal carcinoma cells and elucidated its potential ferroptosis-inducing mechanisms. Morphology alterations of mitochondrial ultrastructure, as observed via transmission electron microscopy, showed that CuB-treated cells undergo ferroptosis. CuB caused intracellular accumulation of iron ions and depletion of glutathione. Detailed molecular mechanism investigation confirmed that CuB both induced widespread lipid peroxidation and downregulated the expression of GPX4, ultimately initiating a multipronged mechanism of ferroptosis. Furthermore, CuB exhibited anti-tumour effects in vitro by inhibiting cellular microtubule polymerization, arresting cell cycle and suppressing migration and invasion. Finally, CuB significantly inhibited tumour progression without causing obvious side effects in vivo. Altogether, our study highlighted the therapeutic potential of CuB as a ferroptosis-inducing agent for nasopharyngeal cancer, and it provided valuable insights for developing effective anti-tumour agents with novel molecular mechanisms derived from natural products.

Feasibility and safety of fine positioning needle-mediated breathing control in CT-guided percutaneous puncture of small lung/liver nodules adjacent to diaphragm.

To assess the efficacy, safety, and feasibility of a separate inserted positioning fine needle-mediated breathing-control technique applied to computed tomography (CT)-guided percutaneous puncture for biopsy or microwave ablation (MWA) of small lung/liver nodules near diaphragm. Total 46 patients with pulmonary/liver small nodules (≤ 3 cm in size) near diaphragm(nodule within 1 cm distance to the diaphragm)were undergone percutaneous biopsy ( n = 15) or MWA (n = 31) under the guidance of CT, and a separate positioning fine needle-mediated breathing-control technique was applied for the precise punctures. CT plain scan was performed to monitor the complications after the procedure. The patient baseline data, operation details, successful rate, major complications as well as radiation dose during the procedure were recorded and analyzed. With the assistance of a fine positioning needle insertion for controlling the breathing, the puncture success rate for biopsy or MWA reached 91.30% (42/46). For biopsy, the mean nodule diameter, nodule distance to the diaphragm, puncture time and radiation dose during CT scan were 2.27 cm ± 0.74, 0.61 cm ± 0.24, 18.67 min ± 6.23, 28.84 mSv ± 6.99, respectively; For MWA, the mean nodule diameter, nodule distance to the diaphragm, puncture time and CT radiation dose were 2.35 cm ± 0.64, 0.69 cm ± 0.23, 38.71 min ± 13.65, 33.02 mSv ± 8.77, respectively. Totally, there were three and four cases found minimal puncture-related hemoptysis and pneumothorax needed no additional treatments, respectively. We recently developed and verified a feasible, safe and highly effective puncture technique with reasonable radiation dose for CT-guided biopsy or MWA for small nodules abutting diaphragm, therefore worthy of extensive application to similar clinical situations.

Targeting B7-H3 via chimeric antigen receptor T cells and bispecific killer cell engagers augments antitumor response of cytotoxic lymphocytes.

BACKGROUND: B7-H3, an immune-checkpoint molecule and a transmembrane protein, is overexpressed in non-small cell lung cancer (NSCLC), making it an attractive therapeutic target. Here, we aimed to systematically evaluate the value of B7-H3 as a target in NSCLC via T cells expressing B7-H3-specific chimeric antigen receptors (CARs) and bispecific killer cell engager (BiKE)-redirected natural killer (NK) cells. METHODS: We generated B7-H3 CAR and B7-H3/CD16 BiKE derived from an anti-B7-H3 antibody omburtamab that has been shown to preferentially bind tumor tissues and has been safely used in humans in early-phase clinical trials. Antitumor efficacy and induced-immune response of CAR and BiKE were evaluated in vitro and in vivo. The effects of B7-H3 on aerobic glycolysis in NSCLC cells were further investigated. RESULTS: B7-H3 CAR-T cells effectively inhibited NSCLC tumorigenesis in vitro and in vivo. B7-H3 redirection promoted highly specific T-cell infiltration into tumors. Additionally, NK cell activity could be specially triggered by B7-H3/CD16 BiKE through direct CD16 signaling, resulting in significant increase in NK cell activation and target cell death. BiKE improved antitumor efficacy mediated by NK cells in vitro and in vivo, regardless of the cell surface target antigen density on tumor tissues. Furthermore, we found that anti-B7-H3 blockade might alter tumor glucose metabolism via the reactive oxygen species-mediated pathway. CONCLUSIONS: Together, our results suggest that B7-H3 may serve as a target for NSCLC therapy and support the further development of two therapeutic agents in the preclinical and clinical studies.

Targeting B7-H3 Immune Checkpoint With Chimeric Antigen Receptor-Engineered Natural Killer Cells Exhibits Potent Cytotoxicity Against Non-Small Cell Lung Cancer.

Chimeric antigen receptor (CAR)-modified natural killer (NK) cell therapy represents a kind of promising anti-cancer treatment because CAR renders NK cells activation and recognition specificity toward tumor cells. An immune checkpoint molecule, B7-H3, plays an inhibitory role in modulation of NK cells. To enhance NK cell functions, we generated NK-92MI cells carrying anti-B7-H3 CAR by lentiviral transduction. The expression of anti-B7-H3 CAR significantly enhanced the cytotoxicity of NK-92MI cells against B7-H3-positive tumor cells. In accordance with enhanced cytotoxicity, the secretions of perforin/granzyme B and expression of CD107a were highly elevated in anti-B7-H3 CAR-NK-92MI cells. Moreover, compared to unmodified NK-92MI cells, anti-B7-H3 CAR-NK-92MI cells effectively limited tumor growth in mouse xenografts of non-small cell lung cancer and significantly prolonged the survival days of mice. This study provides the rationale and feasibility of B7-H3-specific CAR-NK cells for application in adoptive cancer immunotherapy.

Use of chimeric antigen receptor NK-92 cells to target mesothelin in ovarian cancer.

Mesothelin (MSLN) has been reported to be overexpressed in ovarian cancer and may be an ideal target for immunotherapy. Recent studies have suggested that natural killer (NK) cells may be better chimeric antigen receptor (CAR) drivers because of their favorable innate characteristics, such as directly recognizing and killing tumor cells, resulting in a graft-versus-tumor effect but irresponsible for graft-versus-host disease (GVHD). The therapeutic effects of CAR-engineered NK cells targeting MSLN in ovarian cancer have not been evaluated. In this study, MSLN- and CD19-targeted CAR NK-92 (MSLN- and CD19-CAR NK) cells were constructed. Both MSLN- and CD19-CAR molecules were highly expressed on the surface of NK-92 cells following lentiviral gene transduction. MSLN-CAR NK cells specifically killed MSLN-positive ovarian cancer cells (OVCAR-3 and SK-OV-3), rather than MSLN-negative cells (SK-HEP-1), in vitro. Moreover, compared with parental NK-92 cells and CD19-CAR NK cells, stronger cytokine secretion was detected in MSLN-CAR NK cells cocultured with OVCAR-3 and SK-OV-3. Furthermore, MSLN-CAR NK cells effectively eliminated ovarian cancer cells in both subcutaneous and intraperitoneal tumor models; these cells also significantly prolonged the survival of intraperitoneally tumor-bearing mice. These results demonstrate that MSLN-CAR NK cells have robust specific antitumor activity, both in vitro and in vivo, suggesting that mesothelin could be a potential target for CAR NK cells and could be applied in the treatment of ovarian cancer.

Quantitative evaluation of breast density using a dual-energy technique on a digital breast tomosynthesis system.

PURPOSE: Although breast density is considered a strong risk factor of breast cancer, its quantitative assessment is difficult. To investigate a quantitative method of measuring breast density using dual-energy mammographic imaging with central digital breast tomosynthesis in physically uniform and nonuniform phantoms. MATERIAL AND METHODS: The dual-energy imaging unit used a tungsten anode and silver filter with 30 kVp for high-energy images and 20 kVp for low-energy images. Uniform glandular-equivalent phantoms were used to calibrate a dual-energy based decomposition algorithm. The first study used uniform breast phantoms which ranged in thicknesses from 20 to 70 mm, in 10-mm increments, and which provided 30%, 50%, and 70% of breast density. The second study used uniform phantoms ranging from 10% to 90% of breast density. The third study used non-uniform phantoms (at an average density of 50%) with a thickness which ranged from 20 to 90 mm, in 10-mm increments. RESULTS: The root mean square error of breast density measurements was 2.64-3.34% for the uniform, variable thickness phantoms, 4.17% for the uniform, variable density phantoms, and 4.49% for the nonuniform, variable thickness phantoms. CONCLUSION: The dual-energy technique could be used to measure breast density with a margin of error of < 10% using digital breast tomosynthesis.

Investigation of an optimized scanning protocol for the dentomaxillofacial region using 320-slice multidetector computed tomography.

OBJECTIVES: To propose an imaging protocol that provides satisfactory image quality for oral examination while minimizing radiation dosage using 320-slice multidetector CT (MDCT). METHODS: An anthropomorphic head phantom was scanned using 320 MDCT with protocols combining different scanning modes: volume scanning (whole or local) vs helical scanning (80- or 64-slice detectors); tube voltage settings (80 kVp, 120 kVp and 135 kVp); and tube current settings (60 mA, 80 mA, 100 mA and 120 mA). A total of six anatomical bone structures and three anatomical soft-tissue structures were assessed using quantitative and qualitative analysis in the three orthographic planes (axial, sagittal and coronal). A figure of merit (FOM) was used to determine the optimal imaging protocol in terms of tube voltage, tube current and scanning mode. RESULTS: The 80-kVp setting had the worst quantitative and qualitative results (both p < 0.001) compared with the 135-kVp and 120-kVp settings, especially for soft-tissue structures. A significant difference was noted for the scores obtained using a tube current between 120 mA and 60 mA by quantitative analysis, but not by qualitative analysis. Volume scans using either whole or local modes had a significantly higher FOM than helical scanning of 80 or 64 slices. CONCLUSIONS: In 320 MDCT, a protocol using 135 kVp, 80 mA and the volume-scanning mode (whole or local) offers adequate visualization of both soft-tissue and bone structures while keeping the radiation dose as low as possible. This may therefore be considered a first choice among a wide selection of scanning protocols for dentomaxillofacial CT.