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Understanding the biology of the minimal residual disease after targeted therapy of BRAF mutant melanoma



Project Title: „ Understanding the biology of the minimal residual disease after targeted therapy of BRAF mutant melanoma”

Funding: European Regional Development Fund (ERDF), Measure “Support for applied research” 

Project Nr.:

Period: 1 March 2019 – 28 February 2022

Project costs: 648 648,00 EUR

Principle Investigator: Dr. biol. Dace Pjanova


Project summary:

Metastatic melanoma, which arises after initially successful targeted therapy, represents a painful problem for medicine and society due to its high mortality. This project will explore the role of the meiotic component imposed by the melanoma-specific driver mutation of the BRAF kinase onto proliferative cycle in the mechanism of resistance to targeted therapy. The project hypothesis presumes that meiotic and CTA (CTCFL-MAGE A group) proteins ectopically activated by the mutant BRAF modulate the RAS-RAF-MEK-ERK proliferation pathway adapting the BRAF-inhibitor-induced G1/S checkpoint and causing metaphase arrest that enables “mitotic slippage” (also involving down-regulation of the Hippo tumour suppressing pathway) resulting in illicit tetraploidy coupled to reprogramming  and drug escape of a small proportion of resistant and finally de-polyploidised clonogenic cells. This modulated cell cycle, termed the ‘meiomitosis’, is little explored and may open a new avenue in melanoma pathogenesis studies and therapy perspectives. The hypothesis will be tested on melanoma cell cultures and also melanoma patient material. The aim of this project designed as a fundamental research is to address this mechanism as a proof of concept looking for possible new therapeutic targeting, attracting new people to science and increasing the capacity of scientific excellence in the BMC.

Information published 01.03.2019.


1 March 2019 – 31 May 2019

During the initial phase of the project, the origin of cancer triploidity was studied using 15 malignant and five benign tumour types from male patients (altogether 2928 karyotypes) available in the Mitelman database. The in silico meta-analysis showed that the heterogeneity of the karyotype with a pronounced triploid fraction was observed in all types of malignancies. In contrast, chromosome X disomy (most commonly seen as XXY karyotype) positively correlated with triploidity, negatively correlated with diploidity and did not correlate with tetraploidity. An additional in silico analysis based on exome sequencing data is underway. In parallel, a collection of primary melanoma tissues and primary melanoma cell lines obtained from these tissues was tested for the presence of the BRAF V600 mutation using conventional Sanger sequencing. The mutation was found in five out of 17 primary melanoma tissues and one primary melanoma cell line, which was also triple positive for specific melanoma markers. This culture will be further used to test the hypothesis in clinical material.

Information published 31.05.2019.


1 June 2019 – 31 August 2019

Meta-analysis of tumour triploidy, including melanoma, published in “Gene” (Basel). Genotoxic resistance of SK-MEL 28 cell line tested showing high resistance even after 30 Gy irradiation. Mitotic slipping is observed by immunocytochemistry.

Information published 30.08.2019.


1 September 2019 – 30 November 2019

In addition to the meta-analysis of male tumour triploid XXY karyotypes  mentioned above we have published a concept article, which includes own experimental data on the possible mechanism of the origin of triploidy in tumour development (A Digyny Concept for Treatment-Resistant, Near-Triploid Human Cancers, by Salmina et al. , 2019; Genes (Basel). Jul 19, 2019 (10) (7)). Dose studies of the BRAF inhibitor (vemurafenib) and their effect on the development of resistance and morphologically distinct cell subgroups have been initiated in the SK-MEL28 melanoma cell line. In parallel, DNA is extracted from formalin-fixed paraffin-embedded melanoma tissues to detect BRAF and NRAS mutations in patient material.



Figure 1. A conceptual schematic of the diginy like formation of XXY triploid karyotypes in somatic male tumours.

Information published 29.11.2019.


1 December 2019 – 29 February 2020

The manuscript “Mitotic slippage and extranuclear DNA in cancer chemoresistance: a focus on telomeres” has been prepared and submitted to the International Journal of Molecular Sciences.  In this manuscript, we suggest the conversion of the telomerase-driven telomere repair into alternative lengthening of telomeres coupled by homologous recombination with inverted meiosis occurring at the sub-telomere breakage sites. In parallel, BRAF and NRAS mutational status in formalin-fixed paraffin-embedded melanoma tissues is ongoing.

 Information published 28.02.2020. 


1 March 2019 – 31 May 2020

BRAF inhibitor (vemurafenib) effect on the development of resistance and morphologically distinct cell subgroups have been investigated in the SK-MEL28 melanoma cell line. Rare events of mitotic slippage after vemurafenib treatment were observed in SK-MEL28 cells. Increased number of cells in prophase was found pointing out the possibility of activation of meiotic genes. Scientific article “Mitotic slippage and extranuclear DNA in cancer chemoresistance: a focus on telomeres” published in the International Journal of Molecular Sciences (2020 Apr 16, Volume 21 (8): 2779; doi: 10.3390/ijms21082779).

Information published 29.05.2020. 

Mājas lapas izstrādi finansēja ERAF aktivitātes projekts Nr. 2010/0196/2DP/ "Latvijas biomedicīnas pētījumu integrācija Eiropas zinātnes telpā".