NSCLC Archives | Mikhail Blagosklonny Oncotarget

Non-Small Cell Lung Cancer, Targeted Therapy and Drug Resistance

Non-Small Cell Lung Cancer is the most common type of lung cancer, accounting for nearly 85% of all cases. Some patients with NSCLC have genetic mutations, such as ROS1 gene fusions, that drive tumor growth. These patients often respond well to targeted therapies like lorlatinib, a ROS1 inhibitor that blocks cancer growth.

However, cancer is constantly evolving. Over time, it can develop resistance to targeted therapies, leading to treatment failure. Understanding these resistance mechanisms is crucial for precision oncology, the approach of tailoring cancer treatment based on a patient’s unique genetic profile.

The Case Report That Changed Our Understanding

Dr. Jenny L. Wu from Vanderbilt University School of Medicine and Dr. Wade T. Iams from Vanderbilt-Ingram Cancer Center describe a rare case of drug resistance in a 42-year-old man with advanced NSCLC (stage IV) carrying a ROS1 gene rearrangement. Initially, the patient responded to multiple treatments, including entrectinib and later lorlatinib, both FDA-approved ROS1 inhibitors.

After six months on lorlatinib, his cancer began progressing again. To determine why the treatment stopped working, clinicians performed RNA next-generation sequencing (NGS), a diagnostic tool used to detect genetic mutations in cancer cells.

A Hidden Genetic Mutation

The NGS revealed a previously unknown mutation: a RUFY1-RET gene fusion, which had never been linked to lorlatinib resistance before. RET fusions are commonly associated with thyroid cancer and lung adenocarcinoma, but this was the first documented case where a RET fusion emerged as a mechanism of resistance to ROS1 inhibitors.

This discovery suggests that NSCLC can activate alternative survival pathways when ROS1 inhibitors are used, making precision medicine strategies even more critical for advanced lung cancer patients.

A New Treatment Approach

After detecting the RET fusion, clinicians adjusted the patient’s treatment plan by introducing pralsetinib, a RET inhibitor, alongside lorlatinib to target both mutations.

Initially, the combination therapy showed promise. Scans revealed tumor shrinkage, and the patient responded positively. Unfortunately, the response lasted only four months before the cancer progressed again. The patient passed away shortly thereafter, highlighting the urgent need for more durable treatment options for drug-resistant lung cancer.

The Importance of This Case

This is the first documented case of a RET fusion emerging as a resistance mechanism to lorlatinib. It challenges previous assumptions about how NSCLC adapts to targeted therapies and emphasizes the importance of RNA sequencing in detecting hidden resistance mutations.

Standard DNA testing did not detect the RET fusion; only RNA sequencing revealed it. This finding suggests that more sensitive genetic testing should be used when patients develop treatment resistance.

This case also raises new questions about therapy combinations. While the mix of lorlatinib and pralsetinib provided temporary disease control, it was not enough for long-term remission. New strategies are needed to develop more long-lasting treatment combinations for patients who develop resistance.

Future Perspectives and Conclusion

Treatment resistance remains a major challenge in lung cancer care. While targeted therapies have revolutionized treatment, they must continuously adapt to stay ahead of the disease.

Although the combination of pralsetinib and lorlatinib initially showed some effectiveness, the response did not last. In the future, scientists must investigate why some RET fusions make drugs less effective and whether finding these genetic alterations earlier could help change treatment plans before resistance fully sets in.

By uncovering new resistance mechanisms, this case highlights the importance of advanced genetic testing and contributes to the growing field of precision oncology. The more we understand how cancer adapts, the better we can develop smarter, more effective treatments and improve survival rates for lung cancer patients.

Click here to read the full case report in Oncotarget.

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Researchers developed a divergent strategy to treat non-small cell lung cancer (NSCLC).

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Listen to an audio version of this article

The mammalian target of rapamycin (mTOR) operates within two distinct protein complexes—mTOR complex 1 (mTORC1) and complex 2 (mTORC2). These protein complexes are not yet fully understood, as they were only recently identified in humans in 1994. What researchers do know is that mTORC1 is involved in the regulation of many cellular processes and is a key mediator of cell growth and proliferation. mTORC1 is activated by growth factor receptor signals through the PI3K–AKT and RAS–ERK mitogen-activated protein kinase (MAPK) pathways.

The PI3K/AKT/mTOR pathway may be an efficacious target in the treatment of patients with non-small cell lung cancer (NSCLC). This theory is based on the identification of particular gene mutations in NSCLC that are associated with the PI3K/AKT/mTOR pathway. However, previous studies have not yet succeeded in defining an effective monotherapy or combination of therapies that targets this pathway while improving NSCLC patient outcome.

Researchers from Institut Curie, PSL University, Xentech, BioPôle Alfort, Hôpital Foch, and Centre Léon Bérard designed a study using a new methodology to test treatment combinations based on specific targets identified as biomarkers of resistance to PI3K-targeting treatments, and not based on the NSCLC mutations themselves. Their trending research paper was published by Oncotarget in 2021 and entitled, “High in vitro and in vivo synergistic activity between mTORC1 and PLK1 inhibition in adenocarcinoma NSCLC.”

“Our main strategy was therefore, using a panel of NSCLC PDXs, (i) to define predictive markers of response to RAD001 therapy and (ii) to identify possible combinations of treatments that may be able to reverse RAD001 resistance.”

THE STUDY

Researchers tested RAD001/Everolimus (an mTORC1 inhibitor) in vivo using NSCLC Patient-Derived Xenografts (PDXs), which demonstrated high antitumor efficacy. They next aimed to define predictive markers of response to RAD001 using real-time quantitative RT-PCR assays.

“In order to define predictive markers of response to RAD001, we used real-time quantitative RT-PCR assays to quantify the mRNA expression of a large number of selected genes.”

The team found three significantly highly expressed and targetable genes in NSCLC tumors resistant to RAD001: PLK1, CXCR4 and AXL. They then analyzed these genes for their prognostic value among NSCLC patients that were found in the publicly available database KMPLOT. This analysis revealed that of the three genes evaluated, only one high-gene expression was correlated with a negative impact on overall survival of patients with adenocarcinoma: PLK1. Given this data, the researchers next evaluated the in vivo efficacy of RAD001 combined with a PLK1 inhibitor, volasertib, in four PDX models. The RAD001 + volasertib combination demonstrated dramatic efficacy in three of the four models.

“In all tested PDXs, except LCF29, we have observed a significant, but variable, improvement of the antitumor efficacy of RAD001 + volasertib in comparison to each monotherapy (Figure 2A).”

To define this RAD001 + volasertib drug combination’s mechanism of action, the researchers conducted a pharmacodynamics (PD) study. The team then evaluated post-therapeutic proteins involved in the cell cycle, vascularization and carbonic anhydrase IX expression. These results were then validated using in vitro studies.

CONCLUSION

“Our determination of relevant Pi3K-based therapeutic combination(s) was not supported, by the presence of actual molecular abnormalities, nor by physician therapeutic practices, but by the identification of predictive markers of resistance to Pi3K-based monotherapies.”

In summary, the researchers conclude that their study demonstrates that inhibiting both mTORC1 and PLK1 proteins induces synergistic antitumor activity in multiple models of NSCLC. In the discussion section of this paper, the authors detailed the divergent methodology they used to come to their conclusion.

“This methodology may promote more relevant clinical trials and avoid non-efficient combinations, inacceptable toxicities, and expensive and time-consuming studies.”

Click here to read the full research paper, published by Oncotarget.

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Tagged: NSCLC