Australian consensus statement for best practice ROS1 testing in advanced non-small cell lung cancer

Current treatment and novel insights regarding ROS1-targeted therapy in malignant tumors

BACKGROUND

The proto-oncogene ROS1 encodes an intrinsic type I membrane protein of the tyrosine kinase/insulin receptor family. ROS1 facilitates the progression of various malignancies via self-mutations or rearrangements. Studies on ROS1-directed tyrosine kinase inhibitors have been conducted, and some have been approved by the FDA for clinical use. However, the adverse effects and mechanisms of resistance associated with ROS1 inhibitors remain unknown. In addition, next-generation ROS1 inhibitors, which have the advantage of treating central nervous system metastases and alleviating endogenous drug resistance, are still in the clinical trial stage.

METHOD

In this study, we searched relevant articles reporting the mechanism and clinical application of ROS1 in recent years; systematically reviewed the biological mechanisms, diagnostic methods, and research progress on ROS1 inhibitors; and provided perspectives for the future of ROS1-targeted therapy.

RESULTS

ROS1 is most expressed in malignant tumours. Only a few ROS1 kinase inhibitors are currently approved for use in NSCLC, the efficacy of other TKIs for NSCLC and other malignancies has not been ascertained. There is no effective standard treatment for adverse events or resistance to ROS1-targeted therapy. Next-generation TKIs appear capable of overcoming resistance and delaying central nervous system metastasis, but with a greater incidence of adverse effects.

CONCLUSIONS

Further research on next-generation TKIs regarding the localization of ROS1 and its fusion partners, binding sites for targeted drugs, and coadministration with other drugs is required. The correlation between TKIs and chemotherapy or immunotherapy in clinical practice requires further study.

Developments in systemic therapies for the management of lung cancer

Lung cancer accounts for approximately 1 in 10 new cancer diagnoses annually and is responsible for the most cancer-associated deaths in Australia. Despite such figures, there is reason for optimism with many practice-changing developments to report for the management of patients with thoracic malignancies over the last few years. We outline such changes, including the emerging role of immunotherapy in the neoadjuvant and adjuvant setting for patients with localised non-small-cell lung cancer, as well as the established standard of consolidation immunotherapy following definitive chemoradiotherapy for those with locally advanced disease. In the metastatic setting, combination chemotherapy-immunotherapy approaches have become the new paradigm for most patients in the absence of a recognised driver mutation. A range of novel targeted therapies now exist and are Pharmaceutical Benefits Scheme (PBS)-subsidised for targets such as EGFR, ALK and ROS1, with many others, such as KRAS G12C, NTRK, MET, RET and HER2, also with therapies rapidly being developed. Even among patients with small-cell lung cancer, who account for the worst prognoses and until recently have received a chemotherapy regimen that has remained unchanged in over 20 years, there is a new standard-of-care in combination chemotherapy-immunotherapy. Furthermore, immunotherapy and potentially anti-vascular endothelial growth factor agents now also play a role in mesothelioma treatment. Last, given recent developments in immunotherapy, targeted therapy and combination approaches in the non-small-cell lung cancer space, there is an increasing recognition of the diversity of lived experience for such patients and need for survivorship programmes to acknowledge such nuances.

ROS1 rearrangements in lung adenocarcinomas are defined by diffuse strong immunohistochemical expression of ROS1

A small subset of lung adenocarcinomas harbour ROS1 gene arrangements and are amenable to tyrosine kinase inhibitor therapy. Current practice in Australia involves screening for ROS1 rearrangements in adenocarcinomas using ROS1 immunohistochemistry (IHC) followed by confirmatory molecular testing such as fluorescence in situ hybridisation (FISH), if other known genetic driver alterations are absent. The best threshold to determine ROS1 IHC positivity is not well defined, however, and this study aims to determine the optimal threshold for ROS1 IHC screening to identify ROS1-rearranged lung adenocarcinomas. A total of 177 lung adenocarcinomas tested for a ROS1 rearrangement by FISH at our institution between 2017 and 2020 due to presence of ROS1 IHC staining were included in the study. ROS1 IHC staining was assessed by scoring the staining intensity (0, 1, 2, or 3+) and multiplying by the percentage of positive cells to generate an H-score. IHC H-scores were compared with FISH. Of 177 cases, 32 (18%) were ROS1 FISH-positive and 145 (82%) were negative. FISH-positive cases had a median H-score of 300 (range 200-300; mean 290.3) and negative cases had a median H-score of 40 (range 0-300; mean 63). All FISH-positive cases showed strong and diffuse IHC positivity. Using a threshold H-score of 200, the sensitivity of identifying ROS1 rearrangements was 100% and the specificity was 95% amongst cases referred with ROS1 IHC positivity. Adenocarcinomas with a FISH-confirmed ROS1 rearrangement demonstrate diffuse, strong (2-3+) IHC staining. Cases with weak, patchy ROS1 IHC staining are not associated with ROS1 rearrangements and in these cases FISH testing is of little to no utility.

ROS1 rearrangements in non-small cell lung cancer: screening by immunohistochemistry using proportion of cells staining without intensity and excluding cases with MAPK pathway drivers improves test performance

Therapeutically actionable ROS1 rearrangements have been described in 1-3% of non-small cell lung cancer (NSCLC). Screening for ROS1 rearrangements is recommended to be by immunohistochemistry (IHC), followed by confirmation with fluorescence in situ hybridisation (FISH) or sequencing. However, in practise ROS1 IHC presents difficulties due to conflicting scoring systems, multiple clones and expression in tumours that are wild-type for ROS1. We assessed ROS1 IHC in 285 consecutive cases of NSCLC with non-squamous histology over a nearly 2-year period. IHC was scored with ROS1 clone D4D6 (n=270), clone SP384 (n=275) or both clones (n=260). Results were correlated with ROS1 break-apart FISH (n=67), ALK status (n=194), and sequence data of EGFR (n=178) and other drivers, where possible. ROS1 expression was detected in 161/285 cases (56.5%), including 13/14 ROS1 FISH-positive cases. There was no ROS1 expression in one ROS1 FISH-positive case in which sequencing detected an ALK-EML4 fusion, but not a ROS1 fusion. The other 13 ROS1 FISH-positive cases showed moderate to strong staining with both IHC clones. However, one case with a TPM3-ROS1 fusion would have been scored as negative with SP384 and D4D6 clones by some previous criteria. ROS1 expression was also detected in 58/285 cases (20.4%) that had driver mutations in genes other than ROS1. A sensitivity of 100% for detecting a ROS1 rearrangement by FISH was achieved by omitting intensity from the IHC scoring criteria and expression in >0% cells with D4D6 or in ≥50% cells with SP384. Excluding cases with driver events in any MAPK pathway gene (e.g., in ALK, EGFR, KRAS, BRAF, ERBB2 and MET) substantially reduced the number of cases proceeding to ROS1 FISH. Only 15.9% of MAPK-negative NSCLC would proceed to FISH for an IHC threshold of >0% cells with D4D6, with a specificity of 42.4%. For a threshold of ≥50% cells with SP384, only 18.5% of MAPK-negative cases would proceed to FISH, with a specificity of 31.4%. Based on our data we suggest an algorithm for screening for ROS1 rearrangements in NSCLC in which ROS1 FISH is only performed in cases that have been demonstrated to lack activating mutations in any MAPK pathway gene by comprehensive sequencing and ALK IHC, and show staining at any intensity in ≥50% of cells with clone SP384, or >0% cells with D4D6.

Screening for ROS1 fusions in patients with advanced non-small cell lung carcinomas using the VENTANA ROS1 (SP384) Rabbit Monoclonal Primary Antibody

Introduction: The development of several ROS1 inhibitors means that the importance of accurately identifying ROS1-positive lung cancer patients has never been greater. Therefore, it is crucial that ROS1 testing assays become more standardized.Areas covered: Based on primary literature, combined with personal diagnostic and research experience, this review provide a pragmatic update on the use of the recently released VENTANA ROS1 (SP384) Rabbit Monoclonal Primary Antibody.Expert opinion: This assay provides high sensitivity, so it is an excellent analytical option when screening for ROS1 fusions in patients with advanced non-small cell lung carcinomas.

ROS1-dependent cancers - biology, diagnostics and therapeutics

The proto-oncogene ROS1 encodes a receptor tyrosine kinase with an unknown physiological role in humans. Somatic chromosomal fusions involving ROS1 produce chimeric oncoproteins that drive a diverse range of cancers in adult and paediatric patients. ROS1-directed tyrosine kinase inhibitors (TKIs) are therapeutically active against these cancers, although only early-generation multikinase inhibitors have been granted regulatory approval, specifically for the treatment of ROS1 fusion-positive non-small-cell lung cancers; histology-agnostic approvals have yet to be granted. Intrinsic or extrinsic mechanisms of resistance to ROS1 TKIs can emerge in patients. Potential factors that influence resistance acquisition include the subcellular localization of the particular ROS1 oncoprotein and the TKI properties such as the preferential kinase conformation engaged and the spectrum of targets beyond ROS1. Importantly, the polyclonal nature of resistance remains underexplored. Higher-affinity next-generation ROS1 TKIs developed to have improved intracranial activity and to mitigate ROS1-intrinsic resistance mechanisms have demonstrated clinical efficacy in these regards, thus highlighting the utility of sequential ROS1 TKI therapy. Selective ROS1 inhibitors have yet to be developed, and thus the specific adverse effects of ROS1 inhibition cannot be deconvoluted from the toxicity profiles of the available multikinase inhibitors. Herein, we discuss the non-malignant and malignant biology of ROS1, the diagnostic challenges that ROS1 fusions present and the strategies to target ROS1 fusion proteins in both treatment-naive and acquired-resistance settings.

Haimufang decoction, a Chinese medicine formula for lung cancer, arrests cell cycle, stimulates apoptosis in NCI-H1975 cells, and induces M1 polarization in RAW 264.7 macrophage cells

BACKGROUND

Lung cancer has the highest morbidity and mortality in the world and novel treatment strategies are still needed. Haimufang decoction (HMF) is a patented clinical prescription of traditional Chinese medicine for lung cancer treatment. HMF is composed of four herbs and has been applied clinically in advanced cancer patients. However, its therapeutic mechanisms are still unclear. This study aims to elucidate the possible mechanisms of HMF for the treatment of lung cancer.

METHODS

3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay was applied for evaluating the proliferative effect of HMF in lung cancer cells and monocyte macrophage RAW264.7 cells. Flow cytometer was used to detect the effects of HMF on cell cycle and apoptosis, and western blotting was employed to explore the potential apoptotic mechanisms of HMF on lung cancer cells. For immunomodulatory effect, co-culture system was used to detect the activation of macrophage RAW264.7 cells when treated with HMF, and neutral red assay was used to measure the effect of HMF on the phagocytosis of the activated macrophages. Enzyme linked immunosorbent assay, flow cytometer, and immunofluorescence staining method were employed for the investigation on the underlying mechanisms of the immunomodulatory effect on RAW264.7 induced by HMF.

RESULTS

HMF inhibited the proliferation, induced S phase cell cycle arrest, and stimulated apoptosis in lung cancer NCI-H1975 cells, while had negligible cytotoxicity on macrophage RAW264.7 cells. Moreover, HMF could activate macrophage RAW264.7 cells and promote the inhibition activity of RAW264.7 cells against lung cancer cells. And also, HMF activated macrophages and increased their phagocytic activity in a concentration-dependent manner. HMF increased the expression of macrophage activation marker CD40, the level of nitric oxide, the generation of intracellular reactive oxygen species, as well as M1 macrophages cytokines including tumor necrosis factor-α, interleukin-1β, interleukin 12 p70, and interleukin 6. Further investigation showed that HMF induced M1 but not M2 phenotype polarization in RAW264.7 cells.

CONCLUSIONS

HMF can mainly exert anticancer activity via (1) cytotoxicity to human lung cancer cells by proliferation inhibition, cell cycle arrest, and apoptosis induction; and also via (2) immunomodulation via macrophage cells activation and M1 phenotype polarization induction.