Tagged: gene variants

Genetic Alterations in Thyroid Cancer: Resistance to BRAFi and Anaplastic Transformation

February 8, 2024

In this new research perspective, researchers discuss the role of genetic alterations in resistance to BRAF inhibition and anaplastic transformation in thyroid cancer.

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Thyroid cancer is a complex disease with various subtypes and clinical presentations. While some cases can be successfully treated with standard therapy, others present challenges due to resistance to treatment and the development of aggressive forms of the disease. In a new research perspective, researchers Mark Lee and Luc GT Morris from New York Presbyterian Hospital and Memorial Sloan Kettering Cancer Center discuss the recent research that has shed light on the role of genetic alterations in mediating both resistance to BRAF inhibition and anaplastic transformation in thyroid cancer. On January 24, 2024, their paper was published in Oncotarget, entitled, “Genetic alterations in thyroid cancer mediating both resistance to BRAF inhibition and anaplastic transformation.”

“An improved understanding of the molecular basis of thyroid cancer has led to the development of new targeted agents.”

Understanding Thyroid Cancer and its Molecular Landscape

Thyroid cancer is generally characterized by well-differentiated histology and a relatively indolent course. However, a subset of patients presents with more advanced disease or dedifferentiated histologies that are less responsive to standard therapy. These dedifferentiated subtypes include anaplastic thyroid cancers (ATC) and poorly differentiated thyroid cancers (PDTC), which are thought to arise from a process of microevolution from papillary thyroid cancers (PTC).

The mitogen-activated protein kinase (MAPK) pathway plays a crucial role in regulating cell proliferation and differentiation. Mutations in this pathway, particularly in the BRAF gene (specifically the V600E mutation), have been identified in a significant proportion of thyroid cancers. The BRAF V600E mutation leads to constitutive activation of the MAPK pathway, resulting in dedifferentiation and tumor progression.

BRAF Inhibition as a Therapeutic Approach

Given the role of the BRAF V600E mutation in thyroid cancer, targeted agents that inhibit BRAF have been explored as potential treatments. Sorafenib and lenvatinib were the first agents approved for use in thyroid cancer but have shown limited overall survival benefits. More recent agents, such as vemurafenib and dabrafenib, specifically target the V600E mutant oncoprotein and have demonstrated promising results in early trials.

However, despite initial responses, the long-term efficacy of BRAF inhibitors is limited due to the emergence of resistance mechanisms. Multiple compensatory pathways and mutations have been observed in thyroid carcinoma cells that mediate bypass of BRAF blockade, leading to disease progression. These mechanisms can be primary, already present in the tumor, or secondary, acquired over the course of treatment.

Genetic Alterations Associated with Resistance to BRAF Inhibition

Recent studies have identified specific genetic alterations that are associated with resistance to BRAF inhibitors and anaplastic transformation in thyroid cancer. One such alteration is the presence of mutations in the PI3K/AKT/mTOR pathway, particularly in the PIK3CA gene. These mutations paradoxically hyperactivate the ERK pathway when BRAF is inhibited, leading to decreased response to therapy].

Other genetic alterations associated with resistance include mutations in the MAPK/ERK pathway (such as MET amplifications, NF2, NRAS, and RASA1), the SWI/SNF chromatin remodeling complex (ARID2 and PBRM1), and the JAK/STAT pathway (JAK1). These alterations have been observed in tumors that dedifferentiate after treatment with BRAF inhibitors, suggesting their involvement in both resistance and anaplastic transformation.

Mechanisms of Anaplastic Transformation in Thyroid Cancer

Anaplastic transformation, the transition from well-differentiated to dedifferentiated thyroid cancer, is a rare but aggressive form of the disease. The mechanisms underlying anaplastic transformation are not fully understood but likely involve genetic and molecular changes that drive the loss of cellular differentiation.

Ultrastructural analyses have shown that well-differentiated thyroid carcinomas transforming into anaplastic thyroid cancers undergo changes in cellular architecture, including the loss of tight junctions, desmosomes, and cellular polarity. Molecular alterations associated with anaplastic transformation include aneuploidy, increased copy number alterations, and mutations affecting genes such as p53, bcl-2, cyclin D1, β-catenin, Met, c-myc, Nm23, and Ras.

Overlapping Mechanisms of Resistance and Anaplastic Transformation

Recent research has revealed a significant overlap between the genetic alterations associated with resistance to BRAF inhibitors and the development of anaplastic thyroid cancer. Studies have shown that tumors that dedifferentiate after BRAF inhibition are enriched in known genetic alterations that mediate resistance to BRAF blockade, including mutations in the PI3K/AKT/mTOR, MAPK/ERK, SWI/SNF chromatin remodeling complex, and JAK/STAT pathways.

These findings suggest that selective pressures exerted by BRAF inhibition can promote the outgrowth of subclones harboring these mutations, ultimately leading to anaplastic transformation. The complex and multifactorial nature of these compensatory mechanisms underscores the need for alternative treatment strategies to address resistance and improve long-term disease control.

Immune Microenvironment in Resistance and Anaplastic Transformation

The immune microenvironment of thyroid tumors has been a topic of active investigation, as it plays a crucial role in both tumor pathogenesis and drug resistance. While BRAF inhibitors are thought to increase anti-tumor immunity, they may also have competing effects, such as driving tumor infiltration by macrophages. Anaplastic thyroid cancer is associated with changes in the immune milieu, including increased infiltration by macrophages and fibroblasts.

The immunosuppressive microenvironment observed in resistance to BRAF inhibitors and anaplastic evolution suggests a potential role for combined targeted therapy with immunotherapy. Preclinical studies have shown that the combination of BRAF inhibitors with immune checkpoint inhibitors can enhance anti-tumor immune activity. Clinical trials evaluating the efficacy of combined BRAF blockade with immunomodulatory therapies are ongoing, with preliminary results showing promising anti-tumor effects.

Current Approaches and Future Directions

The current standard therapeutic approach for locally advanced, recurrent, metastatic, and dedifferentiated thyroid cancers involves surgical resection and adjuvant radioactive iodine therapy. However, in cases where surgery is not feasible or tumors are resistant to standard therapy, targeted agents have emerged as potential treatment options.

For patients with ATCs harboring the BRAF V600E mutation, neoadjuvant combination kinase inhibition with dabrafenib plus trametinib has shown promise . Other targeted agents, such as everolimus (MTOR inhibitor), crizotinib (MET inhibitor), and PI3K inhibitors, have demonstrated antitumor activity in preclinical and early clinical studies.

Combined BRAF blockade with immunotherapy is also being investigated as a potential treatment strategy. Early clinical trials have shown promising outcomes, with significant partial response rates and stable disease rates in advanced thyroid cancers. However, further studies with long-term follow-up are needed to evaluate the real-world effectiveness of these novel immunotherapies in combination with targeted therapy.

Conclusion

Genetic alterations play a crucial role in mediating both resistance to BRAF inhibition and anaplastic transformation in thyroid cancer. Understanding the mechanisms underlying these processes is essential for developing effective treatment strategies. Targeted therapies, such as BRAF inhibitors, have shown initial promise but are limited by the emergence of compensatory mechanisms.

The identification of specific genetic alterations associated with resistance and anaplastic transformation provides insights into potential therapeutic targets. Combined targeted therapy with immunomodulatory agents is being explored as a means to enhance anti-tumor immune activity and overcome resistance. Ongoing clinical trials will further elucidate the effectiveness of these novel treatment approaches and pave the way for personalized therapies for patients with thyroid cancer.

In conclusion, the study of genetic alterations in thyroid cancer has provided valuable insights into the development of resistance to targeted therapies and the progression to more aggressive forms of the disease. By understanding the underlying mechanisms and identifying potential therapeutic targets, researchers can work towards improved treatment strategies and better outcomes for patients with thyroid cancer.

“Dual-target therapies have been trialed but with continued limitations to long-term disease control. Thyroid tumor dedifferentiation and BRAF inhibitor resistance are also found to be associated with a transition to an immunosuppressed state. Early studies on combined targeted and immune-modulated therapy have demonstrated promising outcomes. Further clinical studies are needed to test real-world effectiveness of these novel immunotherapies with targeted therapy.”

Click here to read the full research perspective in Oncotarget.

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Oncotarget is an open-access, peer-reviewed journal that has published primarily oncology-focused research papers since 2010. These papers are available to readers (at no cost and free of subscription barriers) in a continuous publishing format at Oncotarget.com. Oncotarget is indexed/archived on MEDLINE / PMC / PubMed.

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Predicting Functions of Cancer-Associated Genetic Variants

September 7, 2023

In a new editorial, researchers from the University of Illinois at Urbana-Champaign discuss the value of using computational models to predict the functions of cancer-associated genetic variants.

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How can we understand the role of genetic variations in cancer development and treatment? This is one of the most challenging and important questions in modern biology and medicine. A new editorial paper, by researchers Jun S. Song and Mohith Manjunath from the University of Illinois at Urbana-Champaign, offers a novel discussion involving computational methods to address this question. On August 30, 2023, their editorial was published in Oncotarget, entitled, “Predicting the molecular functions of regulatory genetic variants associated with cancer.”

“To date, over 490,000 genotype-phenotype associations have been discovered through large-scale genome-wide association studies (GWAS) [1]; however, molecular functions of most of these discovered GWAS variants remain unknown.”

In this editorial, the authors review recent advances and challenges in identifying and characterizing the functional effects of genetic variants that affect gene regulation, such as enhancers, promoters, and transcription factors. These variants, also known as expression quantitative trait loci (eQTLs), can modulate the expression levels of genes and influence various cellular processes and phenotypes, including cancer susceptibility and response to therapy.

The authors propose a framework for predicting the molecular functions of eQTLs based on their genomic context, epigenetic marks, chromatin accessibility, and three-dimensional interactions. They also discuss how to integrate multiple types of data and methods to improve the accuracy and interpretability of the predictions. Furthermore, they highlight the potential applications and implications of their approach for cancer research and precision medicine.

“A promising approach to address these challenges is to integrate genomic, epigenomic, transcriptomic and machine learning methods to identify functional genetic variants and characterize their mode of action in regulating target genes.”

Use Case: MITF and MYC

Microphthalmia-associated transcription factor (MITF) and MYC are two proteins of significant interest in cancer research. Due to their roles in gene regulation and their implications in cancer development and progression, they have been distinguished as oncoproteins. MITF and MYC belong to the basic helix-loop-helix (bHLH)-Zip family of transcription factors (TFs) and have a penchant for hexamer E-box motifs. E-box motifs play a crucial role in regulating gene expression by serving as binding sites for TFs, which can activate or repress the transcription of nearby genes. MITF and MYC are active in melanocytes and possibly vie for shared binding sites.

In their recent study, the researchers aimed to investigate how MITF and MYC interact with each other and with the E-box motifs in the melanocyte genome. They hypothesized that MITF and MYC might have different preferences for E-box variants, which could affect their binding affinity and gene regulation. To test this hypothesis, they used chromatin immunoprecipitation followed by sequencing (ChIP-seq) to map the genome-wide binding sites of MITF and MYC in melanocytes. They also used RNA sequencing (RNA-seq) to measure the gene expression changes after knocking down MITF or MYC. By integrating these data sets, they were able to identify the E-box motifs that were enriched or depleted in the binding sites of MITF and MYC, as well as the genes that were differentially expressed after altering their levels.

The results showed that MITF and MYC had distinct preferences for E-box variants, with MITF favoring CACGTG and MYC favoring CACATG. These preferences were consistent with their roles in gene regulation, as MITF was more likely to activate genes involved in melanocyte differentiation and pigmentation, while MYC was more likely to activate genes involved in cell proliferation and metabolism. The researchers also found that MITF and MYC had overlapping binding sites in some regions of the genome, which suggested that they might compete or cooperate with each other depending on the local context. Furthermore, they discovered that some E-box motifs were associated with higher or lower gene expression regardless of the presence of MITF or MYC, which indicated that other factors might also influence the transcriptional outcome.

The study provided new insights into the molecular mechanisms of MITF and MYC in melanocyte biology and cancer. It also demonstrated the utility of computational models for predicting TF binding sites and gene expression based on sequence features. The researchers suggested that future studies could extend their approach to other TFs and cell types, as well as explore the functional consequences of MITF-MYC interactions in vivo.

Conclusion

This editorial paper is a timely and comprehensive overview of the current and future directions in the field of functional genomics of cancer-associated eQTLs. It provides valuable insights and guidance for researchers who are interested in exploring this important and rapidly evolving area. Read the full paper to learn more about how to predict the molecular functions of regulatory genetic variants associated with cancer.

“Effectively integrating these rich resources with GWAS results will continue to help prioritize causative inherited genetic variants and improve our molecular understanding of disease etiology, assisting the discovery of actionable genes to improve human health.”

Click here to read the full editorial in Oncotarget.

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Gene Variants Investigated in Polish Bladder and Kidney Cancer

April 28, 2022

Two gene variants were studied in large-scale cohorts for their potential roles in bladder and kidney cancer among Polish patients.

Genitourinary cancers are a group of cancers that affect components of the urinary tract, including the bladder and kidneys. Worldwide, bladder and kidney cancer impact men at disproportionately higher rates than women. While incidence and mortality rates of bladder cancer in most western European countries have been consistently decreasing, some countries in the region, such as Poland, have seen an increase. Bladder cancer is the 4th most common malignancy in Polish men and the 14th most common malignancy in Polish women. There is currently a need to identify more effective bladder cancer biomarkers and therapeutic targets to develop new effective treatments that improve patient outcomes.

“The association between the NOD2 c.3020insC allele and CDKN2A missense variant c.442G>A (p.P.A148T) and survival of patients with bladder or kidney cancer remains controversial.”

In April of 2022, researchers from Pomeranian Medical University, University of Newcastle and NSW Health Pathology published the first larger-scale study in Poland to describe the clinical characteristics and survival of bladder cancer patients and kidney cancer patients associated with variants in NOD2 and CDKN2A. Their research paper was published in Oncotarget on April 22, 2022, and entitled, “Bladder cancer survival in patients with NOD2 or CDKN2A variants.”

The Study

In this study, the researchers investigated two gene variants—the NOD2 c.3020insC variant and the CDKN2A p.A148T polymorphism—and their role in bladder and kidney cancer in Polish cohorts. This NOD2 variant has been shown to occur in 7.3% of the Polish population. The CDKN2A polymorphism has been found in 3.5% of the Polish population. Therefore, these gene variants could be considered genetic risk factors for cancer. To test this hypothesis, the researchers assembled detailed participant data from a cohort of 706 bladder cancer patients and 410 kidney cancer patients. The team compiled control data from over 5,000 unselected, cancer-free individuals.

“To our knowledge, this is the first larger-scale study describing the clinical characteristics and survival of bladder and kidney cancer patients that is associated with the NOD2 c.3020insC allele and the CDKN2A p.A148T polymorphism in Poland.”

After performing the variant analysis in the cohort of Polish patients with bladder cancer, the team found that 8.9% of these patients carried the NOD2 variant and 5.2% carried the CDKN2A variant. However, their analysis revealed that neither the NOD2 nor the CDKN2A variant played a significant role in the survival of patients with bladder cancer. In performing the variant analysis in the cohort of Polish patients with kidney cancer, they found that 7.3% of these patients carried the NOD2 variant and 3.4% carried the CDKN2A variant. The researchers did not observe any statistically significant relationship between kidney cancer and either variant. However, they were not able to perform a survival analysis in the kidney cancer cohort.

Conclusion

The researchers found that the NOD2 c.3020insC variant and the CDKN2A p.A148T polymorphism were not significantly associated with the survival of bladder cancer patients, regardless of age, cancer family history, smoking status, and sex. To date, this is the first larger-scale study to examine these variants in association with clinical characteristics and survival of Polish patients with bladder cancer.

“In summary, the results of this study indicate that neither the NOD2 c.3020insC variant or the CDKN2A p.A148T polymorphism are associated with the survival of bladder cancer patients regardless of age, cancer family history, smoking status, and sex. Thus, the NOD2 c.3020insC or the CDKN2A p.A148T polymorphism cannot be added to the list of genes that are associated with an increased susceptibility to bladder or kidney cancer at this time.”

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

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Oncotarget is an open-access journal that publishes primarily oncology-focused research papers in a continuous publishing format. These papers are available at no cost to readers on Oncotarget.com. Open-access journals have the power to benefit humanity from the inside out by rapidly disseminating information that may be freely shared with researchers, colleagues, family, and friends around the world.

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