Intra- and inter-tumor heterogeneity in a vemurafenib-resistant melanoma patient and derived xenografts

EMBO Mol Med. 2015 Sep;7(9):1104-18. doi: 10.15252/emmm.201404914.

Abstract

The development of targeted inhibitors, like vemurafenib, has greatly improved the clinical outcome of BRAF(V600E) metastatic melanoma. However, resistance to such compounds represents a formidable problem. Using whole-exome sequencing and functional analyses, we have investigated the nature and pleiotropy of vemurafenib resistance in a melanoma patient carrying multiple drug-resistant metastases. Resistance was caused by a plethora of mechanisms, all of which reactivated the MAPK pathway. In addition to three independent amplifications and an aberrant form of BRAF(V600E), we identified a new activating insertion in MEK1. This MEK1(T55delins) (RT) mutation could be traced back to a fraction of the pre-treatment lesion and not only provided protection against vemurafenib but also promoted local invasion of transplanted melanomas. Analysis of patient-derived xenografts (PDX) from therapy-refractory metastases revealed that multiple resistance mechanisms were present within one metastasis. This heterogeneity, both inter- and intra-tumorally, caused an incomplete capture in the PDX of the resistance mechanisms observed in the patient. In conclusion, vemurafenib resistance in a single patient can be established through distinct events, which may be preexisting. Furthermore, our results indicate that PDX may not harbor the full genetic heterogeneity seen in the patient's melanoma.

Keywords: Melanoma; drug resistance; patient‐derived xenografts; tumor heterogeneity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antineoplastic Agents / pharmacology
  • Antineoplastic Agents / therapeutic use*
  • Drug Resistance, Neoplasm / genetics*
  • Genetic Variation
  • Heterografts
  • Humans
  • Indoles / pharmacology
  • Indoles / therapeutic use*
  • Melanoma / drug therapy*
  • Mutation*
  • Neoplasm Metastasis / drug therapy*
  • Proto-Oncogene Proteins B-raf / genetics
  • Sequence Analysis, DNA
  • Skin Neoplasms / complications
  • Skin Neoplasms / drug therapy*
  • Sulfonamides / pharmacology
  • Sulfonamides / therapeutic use*
  • Vemurafenib

Substances

  • Antineoplastic Agents
  • Indoles
  • Sulfonamides
  • Vemurafenib
  • Proto-Oncogene Proteins B-raf