Purpose: EGFR-targeting mAbs are essential for managing rat sarcoma virus wild-type metastatic colorectal cancer (mCRC), but their limited efficacy necessitates exploring immunologic and metabolic factors influencing response. This study evaluated glutamine metabolism targeting with EGFR inhibition to identify response biomarkers in patients with prior anti-EGFR treatment progression. Patients and Methods: We conducted a phase I/II trial in patients with KRAS wild-type mCRC, combining panitumumab (6 mg/kg) and CB-839 (600 mg/kg or 800 mg/kg), hypothesizing that the dual inhibition of glutamine metabolism and MAPK signaling would enhance outcomes. As study correlatives, we investigated the B-cell activation signature “B-score” and glutamine PET as potential treatment response biomarkers. Results: The combination of panitumumab and CB-839 was tolerable with manageable side effects, including grade 4 hypomagnesemia in four patients, a known panitumumab-related event. Two patients achieved partial response, and five had stable disease, with a 41% disease control rate. Median progression-free survival and overall survival were 1.84 and 8.87 months, respectively. A positive correlation between “B-score” and lesion size reduction suggested its association with clinical benefit (partial response and stable disease). Lower “B-score” correlated with greater tumor avidity for glutamine by PET, indicating B-cell activation sensitivity to glutamine depletion. Conclusions: The combination of CB-839 and panitumumab showed safety and promising preliminary responses, but the study closed early due to CB-839 development termination. The B-cell activation signature “B-score” emerged as a potential biomarker for EGFR and glutaminase inhibition in mCRC, warranting further studies. These findings suggest opportunities to improve immune response and therapies in glutaminolysis-dependent tumors.

Early response assessment is critical for personalizing cancer therapy. Emerging therapeutic regimens with encouraging results in the wild-type (WT) KRAS colorectal cancer (CRC) setting include inhibitors of epidermal growth factor receptor (EGFR) and glutaminolysis. Towards predicting clinical outcome, this preclinical study evaluated non-invasive positron emission tomography (PET) with (4S)-4-(3-[¹⁸F]fluoropropyl)-L-glutamic acid ([¹⁸F]FSPG) in treatment-sensitive and treatment-resistant WT KRAS CRC patient-derived xenografts (PDXs). Tumor-bearing mice were imaged with [¹⁸F]FSPG PET before and one week following the initiation of treatment with either EGFR-targeted monoclonal antibody (mAb) therapy, glutaminase inhibitor therapy, or the combination. Imaging was correlated with tumor volume and histology. In PDX that responded to therapy, [¹⁸F]FSPG PET was significantly decreased from baseline at 1-week post-therapy, prior to changes in tumor volume. In contrast, [¹⁸F]FSPG PET was not decreased in non-responding PDX. These data suggest that [¹⁸F]FSPG PET may serve as an early metric of response to EGFR and glutaminase inhibition in the WT KRAS CRC setting.

Jeong K, et al. J Gastric Cancer. 2021 Jun;21(2):191-202. https://doi.org/10.5230/jgc.2021.21.e18

Pancreatic ductal adenocarcinoma (PDAC) evolves through precursors, yet the protein programs governing early progression remain poorly defined. We applied Deep Visual Proteomics (DVP)—integrating computational pathology, laser microdissection, and mass spectrometry (MS)—to profile normal ducts, acinar-to-ductal metaplasia (ADM), low-grade (LG) and high-grade (HG) pancreatic intraepithelial neoplasia (PanIN), and invasive carcinoma from organ donors and patients with PDAC. Quantifying 9,181 proteins from ∼100 cells per region, we uncovered a molecular field effect in histologically normal ducts and proteomic divergence of LG-PanINs by cancer context. We identified four stage-associated molecular programs. Stress adaptation and immune engagement emerged early in cancer-associated normal ducts. Metabolic reprogramming initiated in normal ducts and intensified across PanIN progression. Mitochondrial remodeling became prominent in HG-PanINs before invasion. MS detected KRAS hotspot mutant peptides within incidental precursor lesions from cancer-free individuals. These findings demonstrate that molecular reprogramming precedes histologic transformation, creating opportunities for earlier detection of lethal cancer. Significance: Artificial intelligence (AI)–guided DVP represents the first in-depth assessment of the proteomic landscapes observed during the multistep progression of pancreatic adenocarcinoma, including histologically normal ducts, ADM, and LG- and HG-PanIN lesions. These data represent a unique resource of candidate biomarkers and interception targets against this lethal disease.

Bae SW, et al. J Gastric Cancer. 2020 Mar;20(1):60-71. https://doi.org/10.5230/jgc.2020.20.e7

Introduction: Measurement of repeatability and reproducibility (R&R) is necessary to realize the full potential of positron emission tomography (PET). Several studies have evaluated the reproducibility of PET using ¹⁸F-FDG, the most common PET tracer used in oncology, but similar studies using other PET tracers are scarce. Even fewer assess agreement and R&R with statistical methods designed explicitly for the task. ¹⁸F-(2S, 4R)-4-fluoro-glutamine (¹⁸F-Gln) is a PET tracer designed for imaging glutamine uptake and metabolism. This study illustrates high reproducibility and repeatability with ¹⁸F-Gln for in vivo research. Methods: Twenty mice bearing colorectal cancer cell line xenografts were injected with ~9 MBq of ¹⁸F-Gln and imaged in an Inveon microPET. Three individuals analyzed the tumor uptake of ¹⁸F-Gln using the same set of images, the same image analysis software, and the same analysis method. Scans were randomly re-ordered for a second repeatability measurement 6 months later. Statistical analyses were performed using the methods of Bland and Altman (B&A), Gauge Reproducibility and Repeatability (Gauge R&R), and Lin’s Concordance Correlation Coefficient. A comprehensive equivalency test, designed to reject a null hypothesis of non-equivalence, was also conducted. Results: In a two-way random effects Gauge R&R model, variance among mice and their measurement variance were 0.5717 and 0.024. Reproducibility and repeatability accounted for 31% and 69% of the total measurement error, respectively. B&A repeatability coefficients for analysts 1, 2, and 3 were 0.16, 0.35, and 0.49. One-half B&A agreement limits between analysts 1 and 2, 1 and 3, and 2 and 3 were 0.27, 0.47, and 0.47, respectively. The mean square deviation and total deviation index were lowest for analysts 1 and 2, while coverage probabilities and coefficients of the individual agreement were highest. Finally, the definitive agreement inference hypothesis test for equivalency demonstrated that all three confidence intervals for the average difference of means from repeated measures lie within our a priori limits of equivalence (i.e. ± 0.5%ID/g). Conclusions: Our data indicate high individual analyst and laboratory-level reproducibility and repeatability. The assessment of R&R using the appropriate methods is critical and should be adopted by the broader imaging community.