Monitoring response to gefitinib in nude mouse tumor xenografts by (18)F-FDG microPET-CT: correlation between (18)F-FDG uptake and pathological response

CircCDKN2B-AS1 interacts with IMP3 to stabilize hexokinase 2 mRNA and facilitate cervical squamous cell carcinoma aerobic glycolysis progression

Background

Circular RNAs (circRNAs) have been reported to play key roles in the development of various cancers. However, the biological functions and clinical significance of most circRNAs are still elusive. The purpose of this study was to explore the function and mechanism of a certain circRNA named circCDKN2B-AS1 in cervical cancer development and its potential value in the clinic.

Methods

qRT-PCR was used to verify the expression level of circCDKN2B-AS1. CCK-8, Transwell, and flow cytometry (FCM) assays were performed to detect cellular proliferation, migration, and apoptosis, respectively. A Seahorse XFe96 Analyzer was used to measure glycolysis metabolism level. RNA pull-down, RNA immunoprecipitation (RIP), actinomycin-D addition assays and Western blotting were used to screen and elucidate the potential mechanisms involved. BALB/c nude mice and zebrafish embryos (AB, WT) were used as animal models to investigate tumorigenesis capability. ¹⁸FDG-microPET/CT imaging and lactic acid (LA) and pyruvic acid (PA) content detection assays were used to detect the level of glucose metabolism in subcutaneous tumors from nude mice.

Results

CircCDKN2B-AS1, a circular isoform of the long noncoding RNA (lncRNA) CDKN2B-AS1, was upregulated in cervical cancer and precancerous tissues. We found that circCDKN2B-AS1 associated with the IMP3 protein depending on a specific binding site and regulated the stability of Hexokinase 2 (HK2) mRNA, the rate-limiting enzyme of the aerobic glycolysis pathway. The expression level of circCDKN2B-AS1 fated the binding of IMP3 to the 3′ untranslated region (UTR) of HK2 mRNA, consequently affecting the malignant cell phenotype and aerobic glycolysis in cervical cancer in vitro and in vivo. Mutant circCDKN2B-AS1, lacking the IMP3 binding site, did not have such effects. Utilization of an inhibitory peptide to block the interaction between circCDKN2B-AS1 and the IMP3 protein impeded the binding of IMP3 to the 3’UTR of HK2 mRNA and suppressed aerobic glycolysis in cervical cancer cells.

Conclusions

Our findings demonstrate that circCDKN2B-AS1 facilitates aerobic glycolysis by sponging the IMP3 protein to stabilize HK2 mRNA, consequently promoting the malignant phenotype in cervical cancer, which may provide a potential approach for cervical cancer therapeutics.

Preclinical Imaging in Targeted Cancer Therapies

Preclinical imaging with radiolabeled probes can provide noninvasive tools to test the efficacy of targeted agents in tumors harboring specific genetic alterations and to identify imaging parameters that can be used as pharmacodynamics markers in cancer patients. The present review will primarily focus on preclinical imaging studies that can accelerate the clinical approval of targeted agents and promote the development of imaging biomarkers for clinical applications. Since only subgroups of patients may benefit from treatment with targeted anticancer agents, the identification of a patient population expressing the target is of primary importance for the success of clinical trials. Preclinical imaging studies tested the ability of new radiolabeled compounds to recognize mutant, amplified, or overexpressed targets and some of these tracers were transferred to the clinical setting. More common tracers such as ¹⁸F-Fluorothymidine and ¹⁸F-Fluorodeoxyglucose were employed in animal models to test the inhibition of the target and downstream pathways through the evaluation of early changes of proliferation and glucose metabolism allowing the identification of sensitive and resistant tumors. Furthermore, since the majority of patients treated with targeted anticancer agents will invariably develop resistance, preclinical imaging studies were performed to test the efficacy of reversal agents to overcome resistance. These studies provided consistent evidence that imaging with radiolabeled probes can monitor the reversal of drug resistance by newly designed alternative compounds. Finally, despite many difficulties and challenges, preclinical imaging studies targeting the expression of immune checkpoints proved the principle that it is feasible to select patients for immunotherapy based on imaging findings. In conclusion, preclinical imaging can be considered as an integral part of the complex translational process that moves a newly developed targeted agent from laboratory to clinical application intervening in all clinically relevant steps including patient selection, early monitoring of drug effects and reversal of drug resistance.

Diffusion-weighted imaging and diffusion kurtosis imaging for early evaluation of the response to docetaxel in rat epithelial ovarian cancer

Background

To investigate diffusion-weighted magnetic imaging (DWI) and diffusion kurtosis magnetic imaging (DKI) for the early detection of the response to docetaxel (DTX) chemotherapy in rat epithelial ovarian cancer (EOC).

Methods

7,12-Dimethylbenz[A]anthracene was applied to induce orthotopic EOC in Sprague–Dawley rats. Rats with EOC were treated with DTX on day 0 (treatment group) or were left untreated (control group). DWI and DKI were performed on days 0, 3, 7, 14 and 21 after treatment. On day 21, the tumors were categorized into the sensitive and insensitive groups according to the size change. The cutoff values of the DWI and DKI parameters for the early response were determined. The experiment was repeated, and the treatment group was divided into the sensitive and insensitive groups according to the initially obtained cutoff values. The DWI and DKI parameters were correlated with tumor size, proliferation, apoptosis and tumor necrosis.

Results

In the sensitive vs. insensitive or control group, significant differences were found in the Δ% of the DWI and DKI parameters (ADC, D and K) from day 3 and in tumor size from day 14. Early on day 7, the Δ% of K had an AUC of 1 and sensitivity and specificity values of 100% and 100%, respectively, to detect the response to DTX using a cutoff value of 19.03% reduction in K. From day 7, significant differences were found in the Δ% of Ki-67 and CA125 in the sensitive vs. control group and from day 14 in the sensitive vs. insensitive group. From day 14, there were significant differences in the Δ% of Bcl-2, apoptosis and tumor necrosis in the sensitive vs. control or insensitive group. The Δ% values of ADC and D were negatively correlated with the Δ% values of tumor size, Ki-67, CA125 and Bcl-2 and were positively correlated with the Δ% values of apoptosis and tumor necrosis. The Δ% of K was positively correlated with the Δ% values of tumor size, Ki-67, CA125 and Bcl-2 and was negatively correlated with the Δ% values of apoptosis and tumor necrosis.

Conclusions

DWI and DKI parameters, especially K, are superior for imaging tumor size for the early detection of the response to DTX chemotherapy in induced rat EOC.

Evaluating Imaging Biomarkers of Acquired Resistance to Targeted EGFR Therapy in Xenograft Models of Human Head and Neck Squamous Cell Carcinoma

Background: Overexpression of EGFR is a negative prognostic factor in head and neck squamous cell carcinoma (HNSCC). Patients with HNSCC who respond to EGFR-targeted tyrosine kinase inhibitors (TKIs) eventually develop acquired resistance. Strategies to identify HNSCC patients likely to benefit from EGFR-targeted therapies, together with biomarkers of treatment response, would have clinical value. Methods: Functional MRI and 18F-FDG PET were used to visualize and quantify imaging biomarkers associated with drug response within size-matched EGFR TKI-resistant CAL 27 (CALR) and sensitive (CALS) HNSCC xenografts in vivo, and pathological correlates sought. Results: Intrinsic susceptibility, oxygen-enhanced and dynamic contrast-enhanced MRI revealed significantly slower baseline R 2 ∗ , lower hyperoxia-induced Δ R 2 ∗ and volume transfer constant Ktrans in the CALR tumors which were associated with significantly lower Hoechst 33342 uptake and greater pimonidazole-adduct formation. There was no difference in oxygen-induced ΔR1 or water diffusivity between the CALR and CALS xenografts. PET revealed significantly higher relative uptake of 18F-FDG in the CALR cohort, which was associated with significantly greater Glut-1 expression. Conclusions: CALR xenografts established from HNSCC cells resistant to EGFR TKIs are more hypoxic, poorly perfused and glycolytic than sensitive CALS tumors. MRI combined with PET can be used to non-invasively assess HNSCC response/resistance to EGFR inhibition.