Efecto antitumoral de la inhibición de las histonas demetilasas KDM6A/KDM6B en tumores con inactivación genética en SMARCA4 y SMARCB1

Abstract

[spa] En los últimos años, los estudios de secuenciación masiva del genoma del cáncer han revelado una prevalencia sorprendentemente alta de mutaciones en genes que codifican elementos reguladores de la cromatina. Algunas de las subunidades que conforman el núcleo del complejo, como SMARCB1 y SMARCA4, se encuentran frecuentemente alteradas en distintos tipos de cánceres, algunos de los cuales con muy pocas oportunidades terapéuticas o incluso nulas. Adicionalmente, el avance en el conocimiento de la biología molecular del cáncer ha permitido importantes mejoras en el diagnóstico y la terapia molecular contra específicos tipos de cáncer y, por consiguiente, cierto incremento de la supervivencia. En especial, la identificación de las bases genéticas y epigenéticas del cáncer ha permitido el desarrollo y uso de nuevos agentes terapéuticos dirigidos, los cuales representan un gran avance en la medicina personalizada contra el cáncer Interesantemente, en trabajos previos de nuestro grupo se describió un posible efecto terapéutico del ácido retinoico (AR) y los glucocorticoides (GC), solos o en combinación con AZA y SAHA, en células de cáncer de pulmón con amplificación de MYC, pero no en células con mutaciones en SMARCA4. Además, estos dos tipos de alteración se muestran de forma exclusiva en cáncer de pulmón, junto con mutaciones en otros miembros del complejo SWI/SNF, hecho que sugiere una posible relación funcional entre MYC y este complejo remodelador de cromatina en cáncer. En este trabajo se observa que, a diferencia de las células con amplificación de MYC, las células con inactivación en SMARCA4 son refractarias al tratamiento con SAHA, hecho que conduce a una acumulación aberrante e inesperada de H3K27me3. Esta anormalidad también se muestra en células con deficiencia en otros miembros del complejo SWI/SNF, como SMARCB1. Específicamente, las células mutantes para SMARCA4 y SMARCB1 presentan niveles significativamente reducidos de expresión de las enzimas desmetilasas de histonas KDM6A/UTX y KDM6B/JMJD3, así como una desregulación en la transactivación de estas enzimas. Esta dependencia de la actividad de KDM6A/B compromete, de forma específica, la viabilidad de estas células tumorales

[eng] Cancer genome-sequencing studies have revealed a notably high prevalence of mutations in genes encoding chromatin regulatory elements: approximately 20% of all diagnosed cancers present a mutation in a subunit of the SWI/SNF chromatin- remodeling complexes. The role of SWI/SNF family was first implicated in tumor development with the discovery of biallelic inactivation of SMARCB1 in the vast majority of rhabdoid tumor (RT). Since then, at least nine different subunits of the SWI/SNF complex have been identified as elements recurrently mutated in various cancers. Importantly, our lab identified frequent SMARCA4 inactivating mutations in human lung cancer (about 20% of Non-Small Cell Lung Cancer). Moreover, genetic inactivation in this gene play a major role as a driver of small cell carcinoma of ovary hypercalcaemic type (SCCOHT), a rare and very aggressive gynaecological malignancy that predominantly occurs in very young women. However, currently there are no therapies that effectively target SMARCA4-deficient tumors, as well as some types of SMARCB1- deficient tumors.

In recent years, advancements in our understanding of molecular biology of cancer have led to significant improvements in both, diagnosis and targeted molecular therapies to target specific cancer types, resulting in a notable increase in survival rates. In particular, the identification of the genetic and epigenetic fundamentals of cancer has facilitated the development and utilization of novel, tailored therapeutic agents, representing a substantial breakthrough in precision medicine in cancer.

Previous findings from our group involved the potential therapeutic impact of administering retinoic acid and glucocorticoids, commonly used in certain malignancies, either individually or in combination with AZA and SAHA, in lung cancer cases exhibiting MYC amplification. However, these treatments did not yield similar effects in lung cancer cases with SMARCA4 deficiency. Additionally, these two types of alterations, along with mutations in other SWI/SNF complex members, were exclusively observed in lung cancer, hinting at a potential functional correlation between MYC and this chromatin remodeling complex in the context of cancer. Taking all this into account, we aimed to understand the biological mechanisms that underlies the different responses to epigenetic inhibitors observed in cells with MYC activation or cells with inactivation of the SWI/SNF complex, to work on the study of new potential epigenetic inhibitors for the treatment of these tumors.

Here, we show that, unlike the cells with amplification of MYC, cells with SMARCA4 inactivation are refractory to the histone deacetylase inhibitor, SAHA, leading to an aberrant accumulation of H3K27me3. This aberrant accumulation is also evidenced in SMARCB1-deficient pediatric tumors. Specifically, SMARCA4 and SMARCB1 mutant cells shown an impaired transactivation and significantly reduced levels of the histone demethylases KDM6A/UTX and KDM6B/JMJD3.Consequent with this, the SMARCA4 and SMARCB1 deficient cancer cells shown a strong dependency on these specific histone demethylases, so its inhibition only in this genetic background context compromises cancer cell viability. Furthermore, administration of the KDM6s inhibitor GSK-J4 demonstrates a strong anti-tumor effect and therapeutic potential in mice orthotopically implanted with SMARCA4-mutant lung cancer cells lines, mice implanted with primary tumors of small cell carcinoma of the ovary, hyper calcemic type (SCCOHT) and mice implanted with SMARCB1-deficient MRT derived from pediatric patients. In this Thesis we highlight the vulnerability of SMARCA4 and SMARCB1 cancer cells to the inhibition of KDM6s inhibitor as a characteristic that could be exploited for treating SMARCA4 and SMARCB1 mutant cancer patients. This may be a great opportunity to develop a precision medicine that impacts a field of a wide range of tumors, some of which currently do not have therapeutic options.