Identification of mutant K-RAS in pituitary macroadenoma

Clinical insights into circulating free-DNA in patients with bone sarcomas and ewing sarcoma

BACKGROUND AND OBJECTIVES

Sarcomas represent a heterogeneous group of malignancies characterized by varying clinical behaviors and treatment responses. Liquid biopsy has emerged as a promising non-invasive method for monitoring tumor dynamics by detecting actionable mutations in cancer patients. The emergence of circulating DNA as a non-invasive biomarker offers promising avenues for improving diagnostic accuracy and treatment monitoring in sarcoma patients.

METHODS

In this study, the authors employed mutation-specific droplet digital PCR (ddPCR) to analyze tumor-derived cell-free DNA, also known as circulating tumor DNA (ctDNA), belonging to plasma samples of sarcoma patients, aiming to characterize mutation profiles in the IDH2 and TP53 genes. Between July 2019 and June 2023, the authors collected and analyzed 38 samples from patients diagnosed with osteosarcoma, chondrosarcoma, or Ewing's sarcoma. Histopathological confirmation of diagnoses was performed, followed by ddPCR analysis on 36 valid plasma samples.

RESULTS

The results showed mutations in three out of thirty-six sarcoma patients. Patient 1 exhibited a 12.6 % mutant IDH2 (R172S) allele fraction, Patient 2 had a 0.27 % mutant TP53 (R175H), and Patient 3 showed a 17 % mutant IDH2 (R172K). Notably, Patients 1 and 2 were diagnosed with chondrosarcoma, while Patient 3 had osteosarcoma.

CONCLUSIONS

The present study provided evidence for the feasibility of ctDNA detection in sarcoma patients, where mutations were found in IDH2 and TP53 genes, including a novel IDH2 mutation in osteosarcoma. The evaluation of ctDNA has the potential to transform clinical strategies in this challenging group of malignancies and this may be further confirmed in larger cohort studies. Continued research efforts are essential to optimize ctDNA detection methods and validate its utility across diverse sarcoma subtypes.

The Role of RAS in CNS Tumors: A Key Player or an Overlooked Oncogene?

This review examines the prevalence, molecular mechanisms, and clinical implications of RAS mutations in Central Nervous System (CNS) tumors, with a particular focus on glioblastoma. We summarize the current understanding of RAS-driven oncogenic pathways, their contribution to tumor progression, and potential therapeutic strategies targeting RAS and its downstream effectors. Although direct RAS mutations are rare in primary CNS tumors, alterations in RAS signaling, such as NF-1 loss and aberrant receptor tyrosine kinase activation, contribute to malignant progression. Furthermore, emerging evidence links RAS mutations to brain metastases, highlighting their significance in CNS oncology. We also discuss recent clinical trials investigating RAS-targeted therapies, including covalent inhibitors, MEK inhibitors, and novel combination approaches. Given the increasing recognition of RAS pathway alterations in CNS malignancies, further research is needed to elucidate their role in tumor biology and explore targeted therapeutic interventions.

Using digital PCR to investigate the prevalence of KRAS variants in pituitary tumours

Pituitary tumours (PT) are formed in the pituitary gland, a small gland situated at the base of the brain. These tumours can be categorized according to their histological origin and hormone production. In surgical series, non-functioning PT are the commonest subtype, followed by functioning somatotroph and corticotroph tumours. Different somatic alterations have been implicated in the pathogenesis of these tumours and the objective of our study was to expand our previous new finding of KRAS pathogenic genetic variants in pituitary tumours. We conducted a digital polymerase chain reaction (PCR) analysis on formalin-fixed paraffin-embedded tissue blocks belonging to 189 patients. The results showed that, from the 184 pituitary tumours with good quality samples, 13 tumours (7.1%) presented mutant KRAS. The median age of the mutated group was 47 years old (range 19-77) and most patients with mutant KRAS tumours were from the female gender (61.5%, 8/13) and non-functioning subtype. For the first-time, mutant KRAS in corticotroph and somatotroph tumours were detected, and the variants showed low allele frequencies. In conclusion, we demonstrated that pituitary tumours might have mutant KRAS, and these data were not previously described probably due to lack of sensitivity of previous technologies. By identifying these variants, even at minimal levels, we open doors to a deeper understanding of the tumour microenvironment, clonal evolution and potential therapeutic targets.

Mechanism-Based Redesign of GAP to Activate Oncogenic Ras

Ras GTPases play a crucial role in cell signaling pathways. Mutations of the Ras gene occur in about one third of cancerous cell lines and are often associated with detrimental clinical prognosis. Hot spot residues Gly12, Gly13, and Gln61 cover 97% of oncogenic mutations, which impair the enzymatic activity in Ras. Using QM/MM free energy calculations, we present a two-step mechanism for the GTP hydrolysis catalyzed by the wild-type Ras.GAP complex. We found that the deprotonation of the catalytic water takes place via the Gln61 as a transient Brønsted base. We also determined the reaction profiles for key oncogenic Ras mutants G12D and G12C using QM/MM minimizations, matching the experimentally observed loss of catalytic activity, thereby validating our reaction mechanism. Using the optimized reaction paths, we devised a fast and accurate procedure to design GAP mutants that activate G12D Ras. We replaced GAP residues near the active site and determined the activation barrier for 190 single mutants. We furthermore built a machine learning for ultrafast screening, by fast prediction of the barrier heights, tested both on the single and double mutations. This work demonstrates that fast and accurate screening can be accomplished via QM/MM reaction path optimizations to design protein sequences with increased catalytic activity. Several GAP mutations are predicted to re-enable catalysis in oncogenic G12D, offering a promising avenue to overcome aberrant Ras-driven signal transduction by activating enzymatic activity instead of inhibition. The outlined computational screening protocol is readily applicable for designing ligands and cofactors analogously.

Recent advances in the use of liquid biopsy to fight central nervous system tumors

Brain tumors are considered one of the deadliest types of cancer, being challenging to treat, especially due to the blood-brain barrier, which has been linked to treatment resistance. The genomic classification of brain tumors has been helping in the diagnostic precision, however tumor heterogeneity in addition to the difficulties to obtain tissue biopsies, represent a challenge. The biopsies are usually obtained either via neurosurgical removal or stereotactic tissue biopsy, which can be risky procedures for the patient. To overcome these challenges, liquid biopsy has become an interesting option by constituting a safer procedure than conventional biopsy, which may offer valuable cellular and molecular information representative of the whole organism. Besides, it is relatively easy to obtain such as in the case of blood (venipuncture) and urine sample collection. In the present comprehensive review, we discuss the newest information regarding liquid biopsy in the brain tumors' field, methods employed, the different sources of bio-fluids and their potential circulating targets.

The Use of Liquid Biopsy in the Molecular Analysis of Plasma Compared to the Tumour Tissue from a Patient with Brain Metastasis: A Case Report

Different cancers have multiple genetic mutations, which vary depending on the affected tumour tissue. Small biopsies may not always represent all the genetic landscape of the tumour. To improve the chances of identifying mutations at different disease stages (early, during the disease course, and refractory stage), liquid biopsies offer an advantage to traditional tissue biopsy. In addition, it is possible to detect mutations related to metastatic events depending on the cancer types analysed as will be discussed in this case report, which describes a patient with brain metastasis and lung cancer that harboured K-RAS mutations both in the brain tumour and in the ctDNA present in the bloodstream.

Clinical Biology of the Pituitary Adenoma

All endocrine glands are susceptible to neoplastic growth, yet the health consequences of these neoplasms differ between endocrine tissues. Pituitary neoplasms are highly prevalent and overwhelmingly benign, exhibiting a spectrum of diverse behaviors and impact on health. To understand the clinical biology of these common yet often innocuous neoplasms, we review pituitary physiology and adenoma epidemiology, pathophysiology, behavior, and clinical consequences. The anterior pituitary develops in response to a range of complex brain signals integrating with intrinsic ectodermal cell transcriptional events that together determine gland growth, cell type differentiation, and hormonal production, in turn maintaining optimal endocrine health. Pituitary adenomas occur in 10% of the population; however, the overwhelming majority remain harmless during life. Triggered by somatic or germline mutations, disease-causing adenomas manifest pathogenic mechanisms that disrupt intrapituitary signaling to promote benign cell proliferation associated with chromosomal instability. Cellular senescence acts as a mechanistic buffer protecting against malignant transformation, an extremely rare event. It is estimated that fewer than one-thousandth of all pituitary adenomas cause clinically significant disease. Adenomas variably and adversely affect morbidity and mortality depending on cell type, hormone secretory activity, and growth behavior. For most clinically apparent adenomas, multimodal therapy controlling hormone secretion and adenoma growth lead to improved quality of life and normalized mortality. The clinical biology of pituitary adenomas, and particularly their benign nature, stands in marked contrast to other tumors of the endocrine system, such as thyroid and neuroendocrine tumors.

Architects of Pituitary Tumour Growth

The pituitary is a master gland responsible for the modulation of critical endocrine functions. Pituitary neuroendocrine tumours (PitNETs) display a considerable prevalence of 1/1106, frequently observed as benign solid tumours. PitNETs still represent a cause of important morbidity, due to hormonal systemic deregulation, with surgical, radiological or chronic treatment required for illness management. The apparent scarceness, uncommon behaviour and molecular features of PitNETs have resulted in a relatively slow progress in depicting their pathogenesis. An appropriate interpretation of different phenotypes or cellular outcomes during tumour growth is desirable, since histopathological characterization still remains the main option for prognosis elucidation. Improved knowledge obtained in recent decades about pituitary tumorigenesis has revealed that this process involves several cellular routes in addition to proliferation and death, with its modulation depending on many signalling pathways rather than being the result of abnormalities of a unique proliferation pathway, as sometimes presented. PitNETs can display intrinsic heterogeneity and cell subpopulations with diverse biological, genetic and epigenetic particularities, including tumorigenic potential. Hence, to obtain a better understanding of PitNET growth new approaches are required and the systematization of the available data, with the role of cell death programs, autophagy, stem cells, cellular senescence, mitochondrial function, metabolic reprogramming still being emerging fields in pituitary research. We envisage that through the combination of molecular, genetic and epigenetic data, together with the improved morphological, biochemical, physiological and metabolically knowledge on pituitary neoplastic potential accumulated in recent decades, tumour classification schemes will become more accurate regarding tumour origin, behaviour and plausible clinical results.

Current opinion on the diagnosis and management of non-functioning pituitary adenomas

INTRODUCTION

Non-functioning pituitary adenomas (NFPAs) are clinically silent tumors and the second most common pituitary adenoma. Surgery is the mainstay of treatment as there is, as yet, no effective medical treatment.

AREAS COVERED

We present current knowledge on the clinical diagnosis, histopathological classification, molecular data, and management strategies in NFPA.

EXPERT OPINION

NFPA is a heterogeneous group of tumors, in respect to their origin and clinical course. In recent years, research on pathology and molecular biology have advanced our knowledge of NFPA pathogenesis. NFPA exhibit, in the majority of cases, an indolent behavior, with satisfactory response to treatment. In aggressive cases, multimodal management is needed; however, even this approach may be insufficient, so the development of new treatments is warranted for better management. In this setting, the understanding of the mechanisms involved in the genesis and progression of NFPA is crucial for the identification and development of directed treatments with higher chances of response.