Concomitant T790M mutation and small-cell lung cancer transformation after acquired resistance to epidermal growth factor receptor-tyrosine kinase inhibitor

Progress of tubulin polymerization activity detection methods

Tubulin, an important target in tumor therapy, is one of the hotspots in the field of antineoplastic drugs in recent years, and it is of great significance to design and screen new inhibitors for this target. Natural products and chemical synthetic drugs are the main sources of tubulin inhibitors. However, due to the variety of compound structure types, it has always been difficult for researchers to screen out polymerization inhibitors with simple operation, high efficiency and low cost. A large number of articles have reported the screening methods of tubulin inhibitors and their biological activity. In this article, the biological activity detection methods of tubulin polymerization inhibitors are reviewed. Thus, it provides a theoretical basis for the further study of tubulin polymerization inhibitors and the selection of methods for tubulin inhibitors.

PTPRT epigenetic silencing defines lung cancer with STAT3 activation and can direct STAT3 targeted therapies

Signal Transducers and Activators of Transcription-3 (STAT3), a potent oncogenic transcription factor, is constitutively activated in lung cancer, but mutations in pathway genes are infrequent. Protein Tyrosine Phosphatase Receptor-T (PTPRT) is an endogenous inhibitor of STAT3 and PTPRT loss-of-function represents one potential mechanism of STAT3 hyperactivation as observed in other malignancies. We determined the role of PTPRT promoter methylation and sensitivity to STAT3 pathway inhibitors in non-small cell lung cancer (NSCLC). TCGA and Pittsburgh lung cancer cohort methylation data revealed hypermethylation of PTPRT associated with diminished mRNA expression in a subset of NSCLC patients. We report frequent hypermethylation of the PTPRT promoter which correlates with transcriptional silencing of PTPRT and increased STAT3 phosphorylation (Y705) as determined by methylation-specific PCR (MSP) and real time quantitative reverse transcription (RT)-PCR in NSCLC cell lines. Silencing of PTPRT using siRNA in H520 lung cancer cell line resulted in increased pSTAT3_Tyr705 and upregulation of STAT3 target genes such as Cyclin D1 and Bcl-X_L expression. We show this association of PRPRT methylation with upregulation of the STAT3 target genes Cyclin D1 and Bcl-X_L in patient derived lung tumour samples. We further demonstrate that PTPRT promoter methylation associated with different levels of pSTAT3_Ty705 in lung cancer cell lines had selective sensitivity to STAT3 pathway small molecule inhibitors (SID 864,669 and SID 4,248,543). Our data strongly suggest that silencing of PTPRT by promoter hypermethylation is an important mechanism of STAT3 hyperactivation and targeting STAT3 may be an effective approach for the development of new lung cancer therapeutics.

Successful sequential treatment of refractory tumors caused by small cell carcinoma transformation and EGFR-T790M mutation diagnosed by repeated genetic testing in a patient with lung adenocarcinoma harboring epidermal growth factor receptor mutations: A case report

NSCLC patients with EGFR mutations respond to EGFR-TKIs; however, the management of refractory tumors to EGFR-TKIs remains unclear. We demonstrated that repeated genetic testing might be useful for detecting resistance mechanisms as well as for decision-making in EGFR mutated NSCLC patients, following the emergence of resistance to the initial EGFR-TKIs. A 69-year-old man was diagnosed with lung adenocarcinoma with an EGFR exon 19 deletion. After tumor re-growth treated with erlotinib and chemotherapy, he was diagnosed with an SCLC transformation and administered chemotherapy to treat the SCLC. After the resistance of chemotherapy, the EGFR-T790M mutation by liquid biopsy was detected and treated him with osimertinib, which resulted in a clinical response.

Sequential occurrence of small cell and non-small lung cancer in a male patient: Is it a transformation?

Lung cancer is one of the leading causes of cancer-related mortality and is categorized into small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC). We present a patient with epidermal growth factor receptor (EGFR)-mutant-NSCLC who developed metastatic SCLC after initial therapy with second-generation EGFR-tyrosine kinase inhibitor, afatinib. A 65-year-old male non-smoker was diagnosed with adenocarcinoma of the right lung, stage IVA (M1a). Due to tumor positivity for EGFR-Exon 19 deletion, the patient was started on oral afatinib, which resulted in a partial response. After ten months of treatment, he presented in the office with abdominal pain, distension, weight loss and jaundice. He had diffuse skeletal and hepatic metastases on PET/CT scan with interval progression of his cancer. Although the recurrence of lung adenocarcinoma was suspected, the patient was diagnosed with SCLC on liver biopsy. He received two cycles of chemotherapy and died due to pneumonia and sepsis.

Primary resistance to osimertinib due to SCLC transformation: Issue of T790M determination on liquid re-biopsy

OBJECTIVES

EGFR T790M mutation is the most common mechanism of resistance to first-/second-generation EGFR tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC) and could be overcome by third-generation EGFR-TKIs, such as osimertinib. Liquid biopsy, a non-invasive technique used to test the presence of the resistant mutation, may help avoiding tissue re-biopsy. However, analysing only circulating-free DNA, information about other less frequent and coexisting resistance mechanisms may remain unrevealed.

MATERIALS AND METHODS

All patients reported in this series participated in the ASTRIS trial, a real world treatment study testing the efficacy of osimertinib (80mg os die) in advanced T790M-positive NSCLC progressed to prior EGFR-TKI. Patients were considered eligible to osimertinib if T790M positive on tissue or plasma samples. In our patients, EGFR molecular testing on blood sample was conducted with digital droplet PCR (ddPCR).

RESULTS

We report our experience of five patients treated with osimertinib after T790M detection on liquid biopsy that presented a disease progression at first tumor assessment mediated by SCLC transformation, as evidenced at tissue re-biopsies. All patients showed low ratio T790M/activating mutation in the blood before osimertinib (lower than 0.03). For three patients, EGFR mutational analysis was T790M-negative when re-assessed by using a less sensitive method (therascreen^®) on the same liquid biopsy sample analysed by ddPCR before osimertinib therapy.

CONCLUSION

Although liquid biopsy is a relevant tool to diagnose T790M presence in NSCLC patients resistant to EGFR-TKI, in case of a low ratio T790M/activating mutation, tissue biopsy should be considered to exclude the presence of SCLC transformation and/or other concomitant resistance mechanisms.

Concomitant T790M mutation and small-cell lung cancer transformation after acquired resistance to epidermal growth factor receptor-tyrosine kinase inhibitor

A 70‐year‐old man was admitted to our hospital with an abnormal chest X‐ray shadow. Bronchoscopy revealed an adenocarcinoma tumour with an epidermal growth factor receptor (EGFR) exon 19 deletion. Positron emission tomography–computed tomography scanning and magnetic resonance imaging showed advanced stage IV lung cancer. He was treated with erlotinib as a first‐line drug, which maintained a clinical response for 16 months. After disease progression, a re‐biopsy was done from the tumour in the right lower lobe. The obtained specimen harboured both small‐cell lung cancer (SCLC) transformation with retention of the EGFR 19 deletion and the development of an EGFR T790M mutation. We came across a very rare condition of concomitant T790M mutation and SCLC transformation after acquired resistance to EGFR‐tyrosine kinase inhibitor.