Gemcitabine Mechanism of Action Confounds Early Assessment of Treatment Response by 3'-Deoxy-3'-[18F]Fluorothymidine in Preclinical Models of Lung Cancer

Voxel-Based Analysis of the Relation of 3'-Deoxy-3'-[18F]fluorothymidine ([18F]FLT) PET and Diffusion-Weighted (DW) MR Signals in Subcutaneous Tumor Xenografts Does Not Reveal a Direct Spatial Relation of These Two Parameters

PURPOSE

Multimodal molecular imaging allows a direct coregistration of different images, facilitating analysis of the spatial relation of various imaging parameters. Here, we further explored the relation of proliferation, as measured by [18F]FLT PET, and water diffusion, as an indicator of cellular density and cell death, as measured by diffusion-weighted (DW) MRI, in preclinical tumor models. We expected these parameters to be negatively related, as highly proliferative tissue should have a higher density of cells, hampering free water diffusion.

PROCEDURES

Nude mice subcutaneously inoculated with either lung cancer cells (n = 11 A549 tumors, n = 20 H1975 tumors) or colorectal cancer cells (n = 13 Colo205 tumors) were imaged with [18F]FLT PET and DW-MRI using a multimodal bed, which was transferred from one instrument to the other within the same imaging session. Fiducial markers allowed coregistration of the images. An automatic post-processing was developed in MATLAB handling the spatial registration of DW-MRI (measured as apparent diffusion coefficient, ADC) and [18F]FLT image data and subsequent voxel-wise analysis of regions of interest (ROIs) in the tumor.

RESULTS

Analyses were conducted on a total of 76 datasets, comprising a median of 2890 data points (ranging from 81 to 13,597). Scatterplots showing [18F]FLT vs. ADC values displayed various grades of relations (Pearson correlation coefficient (PCC) varied from - 0.58 to 0.49, median: -0.07). When relating PCC to tumor volume (median: 46 mm3, range: 3 mm3 to 584 mm3), lung tumors tended to have a more pronounced negative spatial relation of [18F]FLT and ADC with increasing tumor size. However, due to the low number of large tumors (> ~ 200 mm3), this conclusion has to be treated with caution.

CONCLUSIONS

A spatial relation of water diffusion, as measured by DW-MRI, and cellular proliferation, as measured by [18F]FLT PET, cannot be detected in the experimental datasets investigated in this study.

Co-delivery of gemcitabine and cisplatin via Poly (L-glutamic acid)-g-methoxy poly (ethylene glycol) micelle to improve the in vivo stability and antitumor effect

PURPOSE

The intention of the study was to co-delivery gemcitabine and cisplatin with totally different nature by prodrug and micelle strategy to improve its in vivo stability and antitumor effect.

METHODS

A prodrug of gemcitabine (mPEG-PLG-GEM) was synthesized through the covalent conjugation between the primary amino group of gemcitabine and the carboxylic group of poly (L-glutamic acid)-g-methoxy poly (ethylene glycol) (mPEG-PLG). It was prepared into micelles by a solvent diffusion method, and then combined with cisplatin through chelation to prepare gemcitabine and cisplatin co-loaded mPEG-PLG micelles (mPEG-PLG-GEM@CDDP micelles).

RESULTS

Gemcitabine and cisplatin in each micelle group were released more slowly than in solutions. In addition, pharmacokinetics behaviors of them were improved after encapsulated in prodrug micelles. T_1/2z of gemcitabine and cisplatin encapsulated in micelles were prolonged to 6.357 h (mPEG-PLG-GEM), 10.490 h (mPEG-PLG@CDDP), 5.463 h and 12.540 h (mPEG-PLG-GEM@CDDP) compared with GEM@CDDP solutions (T_1/2z = 1.445 h and 7.740 h). The ratio of synergy between gemcitabine and cisplatin (3:1 ~ 1:1(n/n)) was guaranteed in the systemic circulation, thus improving its antitumor effect. The results of biochemical analysis showed that GEM@CDDP-Sol was more toxic to kidneys and marrow compared with mPEG-PLG-GEM@CDDP micelles.

CONCLUSIONS

By prodrug strategy, gemcitabine and cisplatin with totally different nature were prepared into micelles and obtained a better pharmacokinetic behavior. And the dual drug delivery system performed a better in vivo stability and antitumor effect compared with each single drug delivery system in the experiment. Scheme. Schematic of mPEG-PLG-GEM@CDDP micelles' formation and action process.

Inhibition of autophagy flux by sertraline attenuates TRAIL resistance in lung cancer via death receptor 5 upregulation

Tumor necrosis factor‑related apoptosis‑inducing ligand (TRAIL) is a potential target for cancer therapy, owing to its ability to selectively kill cancer cells without causing significant toxicity to normal cells. However, due to the lack of death receptor expression, cancer cells can become highly resistant to TRAIL. Hence, it is vital to develop agents that restore TRAIL efficacy. Sertraline is an antidepressant drug with anticancer properties. To the best of our knowledge, this is the first study to demonstrate that sertraline inhibits autophagic flux and increases the expression of death receptor 5 (DR5) on TRAIL‑resistant lung cancer cells. Inhibition of autophagy using autophagy inhibitors 3‑methyladenine and chloroquine upregulated the expression of DR5 and enhanced TRAIL‑induced apoptosis, as confirmed by the increase of pro‑apoptotic proteins caspase‑8 and caspase‑3. Silencing DR5 expression using DR5 small interfering RNA prevented sertraline‑induced TRAIL‑mediated apoptosis, indicating the role of DR5 in TRAIL‑mediated apoptosis. Overall, sertraline enhanced TRAIL‑mediated apoptosis via the downregulation of AMP‑activated protein kinase phosphorylation, resulting in the inhibition of autophagic flux, upregulation of DR5 expression, and activation of the apoptotic caspase cascade. These data suggested that sertraline could be used to sensitize human lung cancer cells to TRAIL, while also serving as a therapeutic option in cancer patients with depression.

Discovery of ATR kinase inhibitor berzosertib (VX-970, M6620): Clinical candidate for cancer therapy

Chemoresistance, radioresistance, and the challenge of achieving complete resection are major driving forces in the search for more robust and targeted anticancer therapies. Targeting the DNA damage response has recently attracted research interest, as these processes are enhanced in tumour cells. The major replication stress responder is ATM and Rad3-related (ATR) kinase, which is attracting attention worldwide with four drug candidates currently in phase I/II clinical trials. This review addresses a potent and selective small-molecule ATR inhibitor, which is known as VX-970 (also known as berzosertib or M6620), and summarizes the existing preclinical data to provide deep insight regarding its real potential. We also outline the transition from preclinical to clinical studies, as well as its relationships with other clinical candidates (AZD6738, VX-803 [M4344], and BAY1895344). The results suggest that VX-970 is indeed a promising anticancer drug that can be used both as monotherapy and in combination with either chemotherapy or radiotherapy strategies. Based on patient anamnesis and biomarker identification, VX-970 could become a valuable tool for oncologists in the fight against cancer.

Predictive Signatures Inform the Effective Repurposing of Decitabine to Treat KRAS-Dependent Pancreatic Ductal Adenocarcinoma

Mutated KRAS protein is a pivotal tumor driver in pancreatic cancer. However, despite comprehensive efforts, effective therapeutics that can target oncogenic KRAS are still under investigation or awaiting clinical approval. Using a specific KRAS-dependent gene signature, we implemented a computer-assisted inspection of a drug-gene network to in silico repurpose drugs that work like inhibitors of oncogenic KRAS. We identified and validated decitabine, an FDA-approved drug, as a potent inhibitor of growth in pancreatic cancer cells and patient-derived xenograft models that showed KRAS dependency. Mechanistically, decitabine efficacy was linked to KRAS-driven dependency on nucleotide metabolism and its ability to specifically impair pyrimidine biosynthesis in KRAS-dependent tumors cells. These findings also showed that gene signatures related to KRAS dependency might be prospectively used to inform on decitabine sensitivity in a selected subset of patients with KRAS-mutated pancreatic cancer. Overall, the repurposing of decitabine emerged as an intriguing option for treating pancreatic tumors that are addicted to mutant KRAS, thus offering opportunities for improving the arsenal of therapeutics for this extremely deadly disease. SIGNIFICANCE: Decitabine is a promising drug for cancer cells dependent on RAS signaling.

Depicting Changes in Tumor Biology in Response to Cetuximab Monotherapy or Combination Therapy by Apoptosis and Proliferation Imaging Using 18F-ICMT-11 and 18F-FLT PET

Imaging biomarkers must demonstrate their value in monitoring treatment. Two PET tracers, the caspase-3/7-specific isatin-5-sulfonamide 18F-ICMT-11 (18F-(S)-1-((1-(2-fluoroethyl)-1H-[1,2,3]-triazol-4-yl)methyl)-5-(2(2,4-difluoro-phenoxymethyl)-pyrrolidine-1-sulfonyl)isatin) and 18F-FLT (3'-deoxy-3'-18F-fluorothymidine), were used to detect early treatment-induced changes in tumor biology and determine whether any of these changes indicate a response to cetuximab, administered as monotherapy or combination therapy with gemcitabine. Methods: In mice bearing cetuximab-sensitive H1975 tumors (non-small lung cancer), the effects of single or repeated doses of the antiepidermal growth factor receptor antibody cetuximab (10 mg/kg on day 1 only or on days 1 and 2) or a single dose of gemcitabine (125 mg/kg on day 2) were investigated by 18F-ICMT-11 or 18F-FLT on day 3. Imaging was also performed after 2 doses of cetuximab (days 1 and 2) in mice bearing cetuximab-insensitive HCT116 tumors (colorectal cancer). For imaging-histology comparison, tumors were evaluated for proliferation (Ki-67 and thymidine kinase 1 [TK1]), cell death (cleaved caspase-3 and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling [TUNEL]), and target engagement (epidermal growth factor receptor expression) by immunohistochemistry, immunofluorescence, and immunoblotting, respectively. Tumor and plasma were analyzed for thymidine and gemcitabine metabolites by liquid chromatography-mass spectrometry. Results: Retention of both tracers was sensitive to cetuximab in H1975 tumors. 18F-ICMT-11 uptake and ex vivo cleaved caspase-3 staining notably increased in tumors treated with repeated doses of cetuximab (75%) and combination treatment (46%). Although a single dose of cetuximab was insufficient to induce apoptosis, it did affect proliferation. Significant reductions in tumor 18F-FLT uptake (44%-50%; P < 0.001) induced by cetuximab monotherapy and combination therapy were paralleled by a clear decrease in proliferation (Ki-67 decrease, 72%-95%; P < 0.0001), followed by a marked tumor growth delay. TK1 expression and tumor thymidine concentrations were profoundly reduced. Neither imaging tracer depicted the gemcitabine-induced tumor changes. However, cleaved caspase-3 and Ki-67 staining did not significantly differ after gemcitabine treatment whereas TK1 expression and thymidine concentrations increased. No cetuximab-induced modulation of the imaging tracers or other response markers was detected in the insensitive model of HCT116. Conclusion:18F-ICMT-11 and 18F-FLT are valuable tools to assess cetuximab sensitivity depicting distinct and time-variant aspects of treatment response.

Resveratrol sensitizes lung cancer cell to TRAIL by p53 independent and suppression of Akt/NF-κB signaling

AIMS

TRAIL is a promising anticancer agent that has the potential to sensitize a wide variety of cancer or transformed cells by inducing apoptosis. However, resistance to TRAIL is a growing concern. Current manuscript aimed to employ combination treatment to investigate resveratrol induced TRAIL sensitization in NSCLC.

METHOD

A549 and HCC-15 cells were used in an experimental design. Cell viability was determined by morphological image, crystal violet staining and MTT assay. Apoptosis was evaluated by LDH assay, Annexin V and DAPI staining. Autophagy and apoptosis indicator protein were examined by western blotting. TEM and puncta assay was carried out to evaluate the autophagy. MTP and ROS activity was evaluated by JC-1 and H₂DCFDA staining.

FINDINGS

Resveratrol is a polyphenolic compound capable of activation of tumor suppressor p53 and its pro-apoptotic modulator PUMA. Herein, we showed the p53-independent apoptosis by decrease the expression of phosphorylated Akt-mediated suppression of NF-κB that is also substantiated with the downregulation of anti-apoptotic factors Bcl-2 and Bcl-xl in NSCLC, resulting in an attenuation of TRAIL resistance in combined treatment. Furthermore, apoptosis was induced in TRAIL-resistant lung cancer cells with a co-treatment of resveratrol and TRAIL assessed by the loss of MMP, ROS generations which resulting the translocation of cytochrome c from the mitochondria into the cytosol due to mitochondrial dysfunction. Moreover, autophagy flux was not affected by resveratrol-induced TRAIL-mediated apoptosis in NSCLC.

SIGNIFICANCE

Overall, targeting the NF-κB (p65) pathway via resveratrol attenuates TRAIL resistance and induces TRAIL-mediated apoptosis which could be the effective TRAIL-based cancer therapy regimen.

Thymidine Metabolism as a Confounding Factor for 3'-Deoxy-3'-18F-Fluorothymidine Uptake After Therapy in a Colorectal Cancer Model

Noninvasive monitoring of tumor therapy response helps in developing personalized treatment strategies. Here, we performed sequential PET and diffusion-weighted MRI to evaluate changes induced by a FOLFOX-like combination chemotherapy in colorectal cancer xenografts, to identify the cellular and molecular determinants of these imaging biomarkers. Methods: Tumor-bearing CD1 nude mice, engrafted with FOLFOX-sensitive Colo205 colorectal cancer xenografts, were treated with FOLFOX (5-fluorouracil, leucovorin, and oxaliplatin) weekly. On days 1, 2, 6, 9, and 13 of therapy, tumors were assessed by in vivo imaging and ex vivo analyses. In addition, HCT116 xenografts, which did not respond to the FOLFOX treatment, were imaged on day 1 of therapy. Results: In Colo205 xenografts, FOLFOX induced a profound increase in uptake of the proliferation PET tracer 3'-deoxy-3'-18F-fluorothymidine (18F-FLT) accompanied by increases in markers for proliferation (Ki-67, thymidine kinase 1) and for activated DNA damage response (γH2AX), whereas the effect on cell death was minimal. Because tracer uptake was unaltered in the HCT116 model, these changes appear to be specific for tumor response. Conclusion: We demonstrated that 18F-FLT PET can noninvasively monitor cancer treatment-induced molecular alterations, including thymidine metabolism and DNA damage response. The cellular or imaging changes may not, however, be directly related to therapy response as assessed by volumetric measurements.

3'-Deoxy-3'-[18F]Fluorothymidine Uptake Is Related to Thymidine Phosphorylase Expression in Various Experimental Tumor Models

PURPOSE

We recently reported that high thymidine phosphorylase (TP) expression is accompanied by low tumor thymidine concentration and high 3'-deoxy-3'-[18F]fluorothymidine ([18F]FLT) uptake in four untreated lung cancer xenografts. Here, we investigated whether this relationship also holds true for a broader range of tumor models.

PROCEDURES

Lysates from n = 15 different tumor models originating from n = 6 institutions were tested for TP and thymidylate synthase (TS) expression using western blots. Results were correlated to [18F]FLT accumulation in the tumors as determined by positron emission tomography (PET) measurements in the different institutions and to previously published thymidine concentrations.

RESULTS

Expression of TP correlated positively with [18F]FLT SUVmax (ρ = 0.549, P < 0.05). Furthermore, tumors with high TP levels possessed lower levels of thymidine (ρ = - 0.939, P < 0.001).

CONCLUSIONS

In a broad range of tumors, [18F]FLT uptake as measured by PET is substantially influenced by TP expression and tumor thymidine concentrations. These data strengthen the role of TP as factor confounding [18F]FLT uptake.

Defining Clinical Response Criteria and Early Response Criteria for Precision Oncology: Current State-of-the-Art and Future Perspectives

In this era of precision oncology, there has been an exponential growth in the armamentarium of genomically targeted therapies and immunotherapies. Evaluating early responses to precision therapy is essential for “go” versus “no go” decisions for these molecularly targeted drugs and agents that arm the immune system. Many different response assessment criteria exist for use in solid tumors and lymphomas. We reviewed the literature using the Medline/PubMed database for keywords “response assessment” and various known response assessment criteria published up to 2016. In this article we review the commonly used response assessment criteria. We present a decision tree to facilitate selection of appropriate criteria. We also suggest methods for standardization of various response assessment criteria. The relevant response assessment criteria were further studied for rational of development, key features, proposed use and acceptance by various entities. We also discuss early response evaluation and provide specific case studies of early response to targeted therapy. With high-throughput, advanced computing programs and digital data-mining it is now possible to acquire vast amount of high quality imaging data opening up a new field of “omics in radiology”—radiomics that complements genomics for personalized medicine. Radiomics is rapidly evolving and is still in the research arena. This cutting-edge technology is poised to move soon to the mainstream clinical arena. Novel agents with new mechanisms of action require advanced molecular imaging as imaging biomarkers. There is an urgent need for development of standardized early response assessment criteria for evaluation of response to precision therapy.