The first renal cancer unit defined purely based on cytogenetic and molecular genetic analysis is RC associated with the translocation Xp11.2 causing a fusion of the TFE3 gene localized here. This unit includes tumors carrying the translocation t(X;1)(p11.2;q21), which leads to the rise of the PRCC/TFE3, t(X;17)(p11.2;q25) fusion gene, which leads to the rise of ASPSCR1 (ASPL,RCC17)/TFE3, t(X;1)(p11.2;p34) fusion gene that produces the SFPQ(PSF)/TFE3 and inv(X)(p11; q12) fusion gene. This inversion leads to the fusion of NonO (P54NRB) and TFE3 genes.

The TFE3 is a protein belonging to the family of helix-loop-helix transcription factors that bind to intronic enhancers of heavy chain of immunoglobulins. The genes PRCC, PSF and NonO (p54nrb) encode proteins that show homology with the factors involved in pre-mRNA splicing. The product of the NonO gene then also regulates transcription. The ASPSCR (ASPL, RCC17) gene then carries the so called UBX domain that interacts with glucose transporter of type 4 (GLUT4) and thus, affects its localization.

Fusions with genes PRCC and ASPSCR1 maintain the DNA-binding domain of TFE3 gene. Then this gene, substantially intact, falls under the influence of promoters and enhancers of partner genes. It causes its increased expression compared to the normal state, which then contributes to the formation and development of this carcinoma.


The test can be performed using RNA isolated from both unfixed and fixed tissues. With respect to the size of RT-PCR fusion products, unfixed tissue is preferred.

The presence of translocation affecting the TFE3 gene is analyzed using complex of several RT-PCR with primers specific to a particular fusion partner gene TFE3 and FISH gene with TFE3 break apart probe.


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