PMC7667179_01
NGS and RT-qPCR were used to identify the ROS1-FBXL17 and CD74-ROS1 fusions in a patient with advanced lung adenocarcinoma. (A). The ROS1-FBXL17 fusion. The junction point of ROS1 is located on 6q22.1 and another junction point is in the intergenic region, close to FBXL17, on 5q21.3. (B). The CD74-ROS1 fusion. The junction point of ROS1 is located on 6q22.1 and that of CD74 is on 5q33.1. (C). A schematic representation of the ROS1-FBXL17 and CD74-ROS1 fusion protein domain structures. Orange, CD74; green, FBXL17; blue, ROS1. The predicted fusion proteins of ROS1-FBXL17 and CD74-ROS1 are 2476 and 778 amino acids in length, respectively. (D). ROS1 fusion was confirmed using RT-qPCR. Red line, samples from the patient; green line, positive control.
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TP53, APC, MGA, and ZNF217 mutations. The novel ROS1-FBXL17 rearrangement (2476 amino acids) was generated through the fusion of ROS1 exons 1-32 on chr6: q22.1 (5'-3', 1-1776 amino acids) to FBXL17 exons 1-9 on chr5: q21.2 (5'-3', 1-700 amino acid) (Figure 1A and C), while the CD74-ROS1 rearrangement (778 amino acids) was generated through the fusion of CD74 exons 1-6 on chr5: q33.1 (5'-3', 1-207 amino acids) to ROS1 exons 33-43 on chr6: q22.1 (5'-3', 1786-2356 amino acids) (Figure 1B and C). In addition, RNA isolation and reverse transcription were performed in postoperative tissue samples, and real-time PCR (amplification refractory mutation system, ARMS) result confirmed the presence of the CD74-ROS1 fusion for clinical requirement (Figure 1D).
Computed tomography or magnetic resonance imaging showed a sustained response to crizotinib in the mediastinal lymph nodes and disease progression in the cerebellum. (A). After chemotherapy, the mediastinal lymph nodes showed swelling, for which crizotinib was administered as a treatment. (B). The mediastinal lymph nodes shrank significantly, without other measurable niduses after 3 courses of treatment with crizotinib. (C-E). A sustained response to crizotinib was observed, and the nidus was unmeasurable. (F and G). No metastatic lesions were observed in the cerebellum. (H and I). A new lesion was found in the cerebellum and disease progression was observed. (J). The cerebellar lesion was shrunk after received radiotherapy.
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Before undergoing molecular targeting treatments, the patient underwent a computed tomography (CT) examination, which showed that the mediastinal lymph nodes were 1.35 cm (Figure 2A). The mediastinal lymph nodes continued to shrink (from 0.65 cm to unmeasurable) without any other observable metastasis (Figure 2B-D). However, magnetic resonance imaging (MRI) on January 10, 2020 showed a new lesion in the cerebellum (0.69 cm) compared with before (Figure 2F-H), and the patient received continued oral treatment with crizotinib. At the time of the assessment on March 3, 2020, the lesion was still growing in size (1.0 cm), confirming disease progression (Figure 2I). On October 13, 2020 the MRI showed a 0.64 cm lesion in the cerebellum (Figure 2J) and CT showed the mediastinal lymph nodes remained stable (Figure 2E).