KIF5B-RET fusion gene and its correlation with clinicopathological and prognostic features in lung cancer: a meta-analysis

Grifolin Induces Cell Death of Human Lung Cancer A549 Cell Line via Inhibiting KRAS-Mediated Multiple Signaling Pathways

In the current work, grifolin was obtained from the twigs and leaves of Daphne genkwa for the first time and displayed significant growth inhibition against human lung carcinoma A549 cells. Subsequent in vitro antitumor evaluation revealed that grifolin could induce remarkable cell apoptosis and G0/G1 phase arrest, as well as block cell migration and invasion. In addition, grifolin also disrupted cellular energy metabolism by inducing reactive oxygen species, reducing adenosine triphosphate and mitochondrial membrane potential, and damaging DNA synthesis. Further RNA-seq analysis demonstrated that treatment of grifolin on A549 cells led to gene enrichment in MAPK, PI3K/Akt and NF-κB signaling pathways, all of which were inhibited by grifolin according to immunoblotting experiments. Further mechanistical studies disclosed that the expression of a key upstream protein KRAS was also blocked, and the cell death triggered by grifolin could be rescued by a RAS activator ML-099. Moreover, pretreatment of ML-099 on A549 cells could reverse the grifolin-induced downregulation of key proteins in the three aforementioned pathways. These findings indicate that grifolin could induce cell death in A549 cell line by inhibiting KRAS-mediated multiple signaling pathways.

Immune checkpoint inhibitors for RET fusion non-small cell lung cancer: hopes and challenges

Immune ch eckpoint inhibitors (ICIs) represent a milestone in advanced nonsmall cell lung cancer (NSCLC). Nevertheless, NSCLC with known oncogenic drivers has been overlooked in most studies evaluating anti-programmed death-1/programmed death ligand 1. Rearranged during transfection proto-oncogene (RET) gene fusion was identified in 1-2% of NSCLC patients. More recently, two selective RET inhibitors, selpercatinib and pralsetinib, demonstrated higher efficacy and good tolerability. In contrast, the activity of ICIs in RET fusion NSCLC has not been well characterized. Here, we analyzed the clinical data of ICIs and discussed the suitable time to introduce ICIs in RET fusion NSCLC. Finally, we put forward future strategies to adequately maximize the efficacy of ICIs treatment in patients with RET fusion NSCLC in the upcoming era of combination immunotherapies.

Pan-tumor survey of RET fusions as detected by next-generation RNA sequencing identified RET fusion positive colorectal carcinoma as a unique molecular subset

BACKGROUND

RET fusions are driver alterations in cancer and are most commonly found in non-small cell lung cancer and well-differentiated thyroid cancer. However, RET fusion have been reported in other solid tumors.

MATERIAL AND METHODS

A retrospective analysis of RET+ solid malignancies identified by targeted RNA sequencing and whole transcriptome sequencing of clinical tumor samples performed at Caris Life Science (Phoenix, AZ).

RESULTS

As of March 22, 2022, a total of 378 RET+ solid malignancies were identified in 15 different tumor types and carcinoma of unknown primary (CUP) that underwent next-generation RNA sequencing. RET+ NSCLC and RET+ thyroid cancer constituted 66.9% and 11.1% of the RET+ solid malignancies, respectively. RET+ colorectal adenocarcinoma and RET+ breast adenocarcinoma constituted 10.1% and 2.6%, respectively. The estimated frequency of RET fusions within specific tumor types were NSCLC 0.7%, thyroid cancer 3.1%, colorectal cancer 0.2% and breast cancer 0.1%. KIF5B (46.8%) was the most common fusion partner followed by CCDC6 (28.3%) and NCOA4 (13.8%) in RET+ solid tumors. KIF5B-RET was the dominant fusion variant in RET+ NSCLC, NCOA4-RET was the dominant variant in RET+ colorectal carcinoma, and CCDC6-RET was the dominant variant in thyroid cancer. The most common single gene alterations in RET+ tumors were TP53 (34.8%), RASA1 (14.3%) and ARIAD1A (11.6%). RET+ CRC had a high median TMB of 20.0 and were commonly MSI-H.

CONCLUSIONS

RET fusions were identified in multiple tumor types. With a higher median TMB and commonly MSI-H, RET fusion positive CRC may be a unique molecular subset of CRC.

Integrated Analysis Identifies Novel Fusion Transcripts in Laterally Spreading Tumors Suggestive of Distinct Etiology Than Colorectal Cancers

BACKGROUND

Laterally spreading tumors (LSTs) of the colon and rectum are a class of abnormality which spreads laterally and appears ulcerated. They are a subclass of colorectal cancer (CRCs) with higher invasive potential than CRCs. Moreover, the etiology of LST still remains obscure.

METHODS

This study aimed to identify unique fusion transcript(s) in LSTs and evaluate their role in LST development and progression. RNA-Seq data for LST samples from the EMBL-EBI database were used to identify fusion transcripts. An integrated approach using Gene Ontology, pathway analysis, hub gene, and co-expression network analysis functionally characterized fusion transcripts to shed light upon the etiology of LSTs.

RESULT

We identified 48 unique fusion genes in LSTs. GO terms were enriched in mRNA metabolic (p ≤ 2.06E-06), mRNA stabilization (p ≤ 1.60E-05), in cytosol (1.20E-05), RBP (p ≤ 2.30E-04), and RNA binding activity (p ≤ 3.51E-08) processes. Pathway analysis revealed an inflammatory phenotype of LSTs suggesting a distinct etiology than CRCs as pathways were enriched in salmonella infection (p ≤ 4.41 e-03), proteoglycans in cancer (p ≤ 1.18 e-02), and insulin signaling (p ≤ 2.13 e-02). Our exclusion and inclusion criteria and hub gene analysis finally identified 9 hub genes. Co-expression analysis of hub genes identified the most significant transcription factors (NELFE, MYC, TAF1, MAX) and kinases (MAPK14, CSNK2A1, CDK1, MAPK1) which were implicated in various cancer pathways. Furthermore, an overall survival analysis of hub genes was performed. Our predefined criterion resulted in the enrichment of NPM1-PTMA (NPM1: p ≤ 0.005) and HIST1H2BO-YBX1 (YBX1: p ≤ 0.02) fusion transcripts, significantly associated with the patient's overall survival.

CONCLUSION

Our systematic analysis resulted in novel fusion genes in LSTs suggesting a different etiology than CRCs. Fusion transcripts were observed more frequently in non-granular LSTs suggestive of genetically more unstable than granular LST. We hypothesize that NPM1-PTMA and HIST1H2BO-YBX1 could be implicated in LST development and progression and may also serve as a prognostic or diagnostic biomarker in future for better management of LSTs.

A comprehensive overview of the relationship between RET gene and tumor occurrence

RET gene plays significant roles in the nervous system and many other tissues. Rearranged during transfection (RET) mutation is related to cell proliferation, invasion, and migration. Many invasive tumors (e.g., non-small cell lung cancer, thyroid cancer, and breast cancer) were found to have changes in RET. Recently, great efforts have been made against RET. Selpercatinib and pralsetinib, with encouraging efficacy, intracranial activity, and tolerability, were approved by the Food and Drug Administration (FDA) in 2020. The development of acquired resistance is inevitable, and a deeper exploration should be conducted. This article systematically reviewed RET gene and its biology as well as the oncogenic role in multiple cancers. Moreover, we also summarized recent advances in the treatment of RET and the mechanism of drug resistance.

FOXA2 and STAT5A regulate oncogenic activity of KIF5B-RET fusion

KIF5B-RET gene rearrangement occurs in ~1% of lung adenocarcinomas. Recently, targeted agents that inhibit RET phosphorylation have been evaluated in several clinical studies; however, little is known about the role of this gene fusion in driving lung cancer. Immunohistochemistry was used to evaluate the expression of the FOXA2 protein in tumor tissues of patients with lung adenocarcinoma. KIF5B-RET fusion cells proliferated in a cohesive form and grew tightly packed with variable-sized colonies. The expression of RET and its downstream signaling molecules, including p-BRAF, p-ERK, and p-AKT, increased. In KIF5B-RET fusion cells, the intracellular expression of p-ERK was higher in the cytoplasm than in the nucleus. Two transcription factors, STAT5A and FOXA2, exhibiting significantly different expressions at the mRNA level, were finally selected. p-STAT5A was highly expressed in the nucleus and cytoplasm, whereas the expression of the FOXA2 protein was lower; however, it was much higher in the nucleus than in the cytoplasm. Compared with the expression of FOXA2 in the RET rearrangement-wild NSCLC (45.0%), high expression (3+) were observed in most RET rearrangement NSCLCs (94.4%). Meanwhile, KIF5B-RET fusion cells began to increase belatedly from day 7 and only doubled on day 9 in 2D cell culture. However, tumors in mice injected with KIF5B-RET fusion cells began to rapidly increase from day 26. In cell cycle analyses, the KIF5B-RET fusion cells in G0/G1 were increased on day 4 (50.3 ± 2.6%) compared with the empty cells (39.3 ± 5.2%; P = 0.096). Cyclin D1 and E2 expressions were reduced, whereas CDK2 expression slightly increased. pRb and p21 expression was diminished compared with the empty cells, TGF-β1 mRNA was highly expressed, and the proteins were accumulated mostly in the nucleus. Twist mRNA and protein expression was increased, whereas Snail mRNA and protein expression was decreased. Particularly, in KIF5B-RET fusion cells treated with FOXA2 siRNA, the expression of TGF-β 1 mRNA was remarkably reduced but Twist1 and Snail mRNA were increased. Our data suggest that cell proliferation and invasiveness in KIF5B-RET fusion cells are regulated by the upregulation of STAT5A and FOXA2 through the continuous activation of multiple RET downstream signal cascades, including the ERK and AKT signaling pathways. We found that TGF-β1 mRNA, where significant increments were observed in KIF5B-RET fusion cells, is regulated at the transcriptional level by FOXA2.

[Consensus on Postoperative Recurrence Prediction of Non-small Cell Lung Cancer Based on Molecular Markers]

Significant progress has been made in lung cancer screening, surgery, chemoradiation, targeted therapy, and immunotherapy recently. Surgical resection is the most important treatment for localized non-small cell lung cancer (NSCLC) so far, but there are still many patients who develop local recurrence or distant metastases within 5 years of surgery. Currently, the risk factors of recurrence in patients with NSCLC are mainly based on clinical and pathological features, which hardly identify patients at high risk of recurrence accurately. With the development of new detection technologies, a number of molecular markers that may have a predictive risk of recurrence in NSCLC have been discovered over the years. In order to summarize the molecular markers related to postoperative recurrence in NSCLC patients, we have formulated a consensus on the prediction of postoperative recurrence of NSCLC based on molecular markers. This consensus mainly focuses on the early stage NSCLC patients, discusses and summarizes the risk factors of disease recurrence from the molecular level. It is hoped that more and more valuable information can be provided for the management of patients, so as to provide more guidance for the perioperative management of the patients with early stage NSCLC in the future.
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External control cohorts for the single-arm LIBRETTO-001 trial of selpercatinib in RET+ non-small-cell lung cancer

Background

Data for selpercatinib [a selective REarranged during Transfection (RET) inhibitor] from a single-arm trial (LIBRETTO-001, NCT03157128) in RET-fusion-positive advanced/metastatic non-small-cell lung cancer (NSCLC) were used in combination with external data sources to estimate comparative efficacy [objective response rate (ORR), progression-free survival, and overall survival (OS)] in first- and second-line treatment settings.

Methods

Patient-level data were obtained from a de-identified real-world database. Patients diagnosed with advanced/metastatic NSCLC with no prior exposure to a RET inhibitor and one or more prior line of therapy were eligible. Additionally, individual patient-level data (IPD) were obtained from the pemetrexed + platinum arm of KEYNOTE-189 (NCT03950674, first line) and the docetaxel arm of REVEL (NCT01168973, post-progression). Patients were matched using entropy balancing, doubly robust method, and propensity score approaches. For patients with unknown/negative RET status, adjustment was made using a model fitted to IPD from a real-world database.

Results

In first-line unadjusted analyses of the real-world control, ORR was 87.2% for LIBRETTO-001 versus 66.7% for those with RET-positive NSCLC (P = 0.06). After adjustment for unknown RET status and other patient characteristics, selpercatinib remained significantly superior versus the real-world control for all outcomes (all P < 0.001 except unadjusted RET-fusion-positive cohort). Similarly, outcomes were significantly improved versus clinical trial controls (all P < 0.05).

Conclusions

Findings suggest improvement in outcomes associated with selpercatinib treatment versus the multiple external control cohorts, but should be interpreted with caution. Data were limited by the rarity of RET, lack of mature OS data, and uncertainty from assumptions to create control arms from external data.

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Single-arm trials are limited by the lack of a comparison arm, and external controls are needed.

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Multiple methodological approaches with various external control arms evaluated the comparative efficacy of selpercatinib.

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Findings suggest that selpercatinib is associated with significantly improved clinical outcomes versus standard therapies.

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Results should be considered exploratory and hypothesis generating due to the limitations of this study.

Addressing challenges with real-world synthetic control arms to demonstrate the comparative effectiveness of Pralsetinib in non-small cell lung cancer

As advanced non-small cell lung cancer (aNSCLC) is being increasingly divided into rare oncogene-driven subsets, conducting randomised trials becomes challenging. Using real-world data (RWD) to construct control arms for single-arm trials provides an option for comparative data. However, non-randomised treatment comparisons have the potential to be biased and cause concern for decision-makers. Using the example of pralsetinib from a RET fusion-positive aNSCLC single-arm trial (NCT03037385), we demonstrate a relative survival benefit when compared to pembrolizumab monotherapy and pembrolizumab with chemotherapy RWD cohorts. Quantitative bias analyses show that results for the RWD-trial comparisons are robust to data missingness, potential poorer outcomes in RWD and residual confounding. Overall, the study provides evidence in favour of pralsetinib as a first-line treatment for RET fusion-positive aNSCLC. The quantification of potential bias performed in this study can be used as a template for future studies of this nature.

Real-world data (RWD) based control arms provide an option to compare the effectiveness of single-arm trials. By performing multiple quantitative bias analyses to alleviate concerns about trial-RWD comparability, here the authors show that the RET inhibitor pralsetinib provides survival benefit in patients with RET fusion-positive non-small cell lung cancer from the ARROW single-arm trial, (NCT03037385) when compared to pembrolizumab monotherapy and pembrolizumab with chemotherapy RWD cohorts.

Research Progress on RET Fusion in Non-Small-Cell Lung Cancer

Great progress has been made in the treatment of driver gene-positive Non- Small Cell Lung Cancer (NSCLC) in recent years. RET fusion was seen in 0.7% to 2% of NSCLC and was associated with younger age and never-smoker status. The pralsetinib and selpercatinib for RET fusion NSCLC was recommended by the 2021 NSCLC treatment guidelines. This review outlines the research progress in the treatment of RET fusion NSCLC, identifies current challenges and describes proposals for improving the outlook for these patients.

Pralsetinib treatment for multiple RET fusions in lung adenocarcinoma: a case report

Despite recent advances in treatments and knowledge of biomarkers, patients with metastatic lung cancer have a 5-year survival rate of 5%. Rearranged during transfection (RET) fusions occur in 1% to 2% of lung cancer patients. Pralsetinib has been used to treat non-small cell lung cancer with a single RET fusion; however, there have been no reports regarding its use in patients with multiple RET fusions. Genetic mutations in tumor tissues were tested using Amplification Refractory Mutation System-PCR and next-generation sequencing (NGS). Pleural fluids obtained from a male patient with non-small cell lung cancer were also used to detect genetic aberrations by NGS. Pleural fluid-based NGS revealed three RET rearrangements: CCDC6-RET (C2:R12), RET-NRG3 (R11:N3), and CCDC6-RET (C1:R12). All three rearrangements were targeted by pralsetinib, a RET fusion inhibitor. Pralsetinib drastically improved the patient’s condition within 4 days, and a partial response was achieved 1 week after pralsetinib was administered. We report for the first time the important clinical observation of a patient with multiple RET fusions who was effectively treated with pralsetinib.

Efficacy of immune checkpoint inhibitor therapy in patients with RET fusion-positive non-small-cell lung cancer

Aim: To describe outcomes of patients with rearraned during transfection (RET) fusion-positive non-small-cell lung cancer (NSCLC) who received immune checkpoint inhibitor (ICI)-based treatments in the US. Patients & methods: Using de-identified Flatiron Health-Foundation Medicine NSCLC Clinico-Genomic and Guardant Health databases, treatment patterns and outcomes of 69 patients with advanced/metastatic RET fusion-positive NSCLC who received ICI-based treatment were described. Results: Median real-world progression-free survival and overall survival months were 4.2 (95% CI: 1.4-8.4) and 19.1 (6.9-not reached), respectively, among patients in Clinico-Genomic database (n = 17) receiving first-line ICI-based therapy. In the Guardant Health database, progression-free survival was unavailable, and the median overall survival was not reached (n = 29). Conclusion: Outcomes associated with ICI-based treatments in the first-line setting among patients with RET fusion-positive NSCLC are consistent with unselected populations reported in literature.

Characteristics and outcomes of patients with RET-fusion positive non-small lung cancer in real-world practice in the United States

BACKGROUND

Contradictory and limited data are available about the presentation and outcomes of patients with RET-fusion positive metastatic NSCLC as compared to patients without RET fusions. This observational study utilizing a linked electronic health records (EHR) database to genomics testing results was designed to compare characteristics, tumor response, progression-free (PFS) and overall survival (OS) outcomes by RET fusion status among patients with metastatic NSCLC treated with standard therapies.

METHODS

Adult patients with metastatic NSCLC with linked EHR and genomics data were eligible who received systemic anti-cancer therapy on or after January 1, 2011. Adjusted, using all available baseline covariates, and unadjusted analyses were conducted to compare tumor response, PFS and OS between patients with RET-fusion positive and RET-fusion negative disease as detected by next-generation sequencing. Tumor response outcomes were analysed using Fisher's exact test, and time-to-event analyses were conducted using Cox proportional hazards model.

RESULTS

There were 5807 eligible patients identified (RET+ cohort, N = 46; RET- cohort, N = 5761). Patients with RET fusions were younger, more likely to have non-squamous disease and be non-smokers and had better performance status (all p < 0.01). In unadjusted analyses, there were no significant differences in tumor response (p = 0.17) or PFS (p = 0.06) but OS was significantly different by RET status (hazard ratio, HR = 1.91, 95% CI:1.22-3.0, p = 0.005). There were no statistically significant differences by RET fusion status in adjusted analyses of either PFS or OS (PFS HR = 1.24, 95% CI:0.86-1.78, p = 0.25; OS HR = 1.52, 95% CI: 0.95-2.43, p = 0.08).

CONCLUSIONS

Patients with RET fusions have different baseline characteristics that contribute to favorable OS in unadjusted analysis. However, after adjusting for baseline covariates, there were no significant differences in either OS or PFS by RET status among patients treated with standard therapy prior to the availability of selective RET inhibitors.