Tracking sub-clonal TP53 mutated tumor cells in human metastatic renal cell carcinoma

Abstract

Renal Cell Carcinomas (RCCs) are heterogeneous tumors with late acquisition of TP53 abnormalities during their evolution. They harbor TP53 abnormalities in their metastases. We aimed to study TP53 gene alterations in tissue samples from primary and metastatic RCCs in 36 patients followed up over a median of 4.2 years, and in xenografted issued from primary RCCs.In 36 primary RCCs systematically xenografted in mice, and in biopsies of metastases performed whenever possible during patient follow-up, we studied p53-expressing tumor cells and TP53 gene abnormalities.We identified TP53 gene alterations in primary tumors, metastases and xenografts.Quantification of tumors cells with TP53 gene alterations showed a significant increase in the metastases compared to the primary RCCs, and, strikingly, the xenografts were similar to the metastases and not to the primary RCCs from which they were derived.Using laser-microdissection of p53-expressing tumor cells, we identified TP53-mutated tumor cells in the xenografts derived from the primary RCC, and in a lung metastasis later developed in one patient. The mutation enabled us to track back their origin to a minority sub-clone in the primary heterogeneous RCC.Combining in situ and molecular analyses, we demonstrated a clonal expansion in a living patient with metastatic RCC.

Clinical Outcomes of TP53 Mutations in Cancers

“…Because TP53 is ubiquitously altered in cancers, TP53 mutations are a tool to confirm the provenance of PDTX (Park et al 2013;Walters et al 2013;Dodbiba et al 2015). Moreover, selection pressures that lead to expansion of aggressive clones on implantation of primary tumors appear to replicate metastatic colonization such that TP53 mutations found in PTDX can serve as a beacon to track the origin of metastases back to minor subclones present in the primary tumors (Bousquet et al 2015). Additional resources and further development are needed before PTDX can become an integral part of a cancer patient's clinical care as a platform to help define therapies based on the molecular make-up of an individual tumor.…”

Patient-Derived Xenograft: An Adjuvant Technology for the Treatment of Metastatic Disease

“…One major limitation is the low engraftment rate of patient-derived xenografts, usually under 20% for localized primary tumors grafted subcutaneously [28,31,33,49]. Certain experimental conditions may significantly increase this rate: orthotopic grafting, grafting under the renal capsule [35,50], or estradiol supplementation for breast cancer xenografts [35].…”

“…We established xenograft models of human primary RCCs, with an engraftment rate of 5% in case of localized disease, and of 36% in case of metastatic disease at diagnosis [31,49]. For each xenograft model, we compared the primary tumor and the corresponding tumor xenografts at the first passage.…”

La résistance aux traitements antiangiogéniques

“…Dans ces modèles, une stabilité histologique et moléculaire par rapport à la tumeur d'origine peut être observée [45] et la stabilité vis-à-vis de la réponse aux traitements antiangiogéniques est également retrouvée. Cependant, la souris athymique ne présentant pas de lymphocytes cytotoxiques (LT8, lymphocytes T CD8 + ), il est important de relier ces résultats à la nature du tissu d'origine et aux données cliniques, et d'évaluer, dans les tissus, l'infiltration des LT8 et l'expression de PDL-1 (programmed deathligand 1), inhibiteur des LT8, qui peut varier selon le type de tumeur [46].…”

“…La microdissection de cellules endothéliales réalisée à partir de biopsies de métastases, confirme ces observations [24]. Nous avons montré que les modèles expérimentaux précliniques que nous avons développés sont pertinents car la plupart des tumeurs aptes à se développer dans la souris athymique sont les clones les plus agressifs [23,24,45,49]. La possibilité d'identifier différents marqueurs, notamment au niveau des niches de précurseurs endothé-liaux, ouvre une voie nouvelle dans la prise en charge des traitements antiangiogéniques.…”