Her-2/neu c-erbB-2 gene evaluation in breast cancer; samples with ambiguous FISH results

Konference: 2009 5. sympózium a workshop molekulární patologie a histo-cyto-chemie

Kategorie: Nádorová biologie/imunologie/genetika a buněčná terapie

Téma: Postery

Číslo abstraktu: p012

Autoři: RNDr. Radek Trojanec, Ph.D.; MUDr. Vladimíra Koudeláková (Palková); prof. MUDr. Zdeněk Kolář, CSc.; Mgr. Jitka Berkovcová, Ph.D.; RNDr. Božena Braunerová; MUDr. Kateřina Bouchalová (Špačková), Ph.D.; Prof. RNDr. Miloš Tichý, CSc.; Mgr. Veronika Krejčí; prof. MUDr. Bohuslav Melichar, Ph.D.; Mgr. Marta Dziechciarková, Ph.D.; MUDr. Karel Cwiertka, Ph.D.; doc. MUDr. Marián Hajdúch, Ph.D.

Amplification and/or overexpression of Her-2/neu indicates unfavourable prognosis in breast cancer patients. Genetically tailored therapy with trastuzumab (Herceptin´) shows great benefit in these individuals. Her-2/neu status is crucial for effective indication of trastuzumab treatment. In the Czech Republic, Her-2/neu status is evaluated by FISH and immunohistochemistry at six Reference Centres (Laboratories of Predictive Medicine). However, some samples cannot be evaluated by FISH due to DNA degradation and those tumors are evaluated by quantitative real-time PCR for Her-2/neu gene. Moreover, due to polysomy of chromosome 17 (CH17) at least 5-7 % of patients are not indicated for trastuzumab treatment as they do not fulfill the criteria of Her-2/neu: CH17 ratio >2.2. The efficacy of trastuzumab in polysomic patients has not yet been confirmed. In the Czech Republic, such patients are indicated for trastuzumab treatment only when they are immunohistochemically positive (3+).
More than 2818 breast cancer samples were evaluated in our institution over a period of seven years by fluorescence in situ hybridisation assay. Overall, 148 (5.25 %) cases failed to be concluded by FISH. Absence of cancer cells and/or DNA degradation in the tumor biopsy were the major causes of the failure. For such cases, quantitative real-time PCR comparing the Her-2/neu gene status to reference genes dck, gcs1 and epn2 was established. Among 148 cases which failed using FISH technique, we have successfully investigated 77 patient samples by qRT-PCR achieving unambiguous results in 78 % (60/77). In 13.8 % (368/2670) cases, polysomy of CH17 was detected by centromeric probe (CEP17). Using locus specific probe mapping of 17p11.2 region, we found that 57 % (212/368) of such a ´polysomic cases´ contain only 2 copies of CH17. We found in some instances, the hybridization of centromeric probe was not specific enough and the probe also hybridized to centromeres of other chromosomes or the cells showed complex cytogenetic rearrangements which misrepresent the number of CH17.

Acknowledgements: Project was supported by grants MSM6198959216 and LC07017. Special thanks go to all cooperating departments, and health insurance companies.

Datum přednesení příspěvku: 24. 4. 2009