Protein multiplicity can lead to misconduct in western blotting and misinterpretation of immunohistochemical staining results, creating much conflicting data.

Western blotting (WB) and immunohistochemical staining (IHC) are common techniques for determining tissue protein expression. Both techniques require a primary antibody specific for the protein in question. WB data is band(s) on a membrane while IHC result is a staining on a tissue section. Most human genes are known to produce multiple protein isoforms; in agreement with that, multiple bands are often found on the WB membrane. However, a common but unspoken practice in WB is to cut away the extra band(s) and present for publication only the band of interest, which implies to the readers that only one form of protein is expressed and thus the data interpretation is straightforward. Similarly, few IHC studies discuss whether the antibody used is isoform-specific and whether the positive staining is derived from only one isoform. Currently, there is no reliable technique to determine the isoform-specificity of an antibody, especially for IHC. Therefore, cutting away extra band(s) on the membrane usually is a form of misconduct in WB, and a positive staining in IHC only indicates the presence of protein product(s) of the to-be-interrogated gene, and not necessarily the presence of the isoform of interest. We suggest that data of WB and IHC involving only one antibody should not be published and that relevant reports should discuss whether there may be protein multiplicity and whether the antibody used is isoform-specific. Hopefully, techniques will soon emerge that allow determination of not only the presence of protein products of genes but also the isoforms expressed.

Subtipos moleculares del cáncer de mama: implicaciones pronósticas y características clínicas e inmunohistoquímicas / Molecular subtypes of breast cancer: prognostic implications and clinical and immunohistochemical characteristics

Fundamento. Los carcinomas de mama representan un grupoheterogéneo de tumores, tanto en su comportamiento clínicocomo pronóstico. El objetivo del presente trabajo es clasificarlos carcinomas de mama en subtipos moleculares mediantemarcadores inmunohistoquímicos y analizar las característicasclinicopatológicas e inmunohistoquímicas y los patronesde supervivencia y recaída de los distintos subtipos.Material y métodos. Se han clasificado 272 pacientes condiagnóstico de carcinoma de mama en cinco subtipos: carcinomasde mama de tipo basal, de tipo HER2, de tipo luminalA, de tipo luminal B y normal.Resultados. Los carcinomas de mama más frecuentes fueronlos de tipo luminal A (62,5%), carcinomas de tipo luminal B(18%), carcinomas de tipo HER2 (9,9%), carcinomas de tipobasal (8,4%) y los de fenotipo normal (1,4%). Los carcinomasde mama de tipo luminal mostraron ser, con mayor frecuencia,de forma significativa, tumores bien diferenciados, depequeño tamaño tumoral, con ganglios axilares negativos,estadio precoz en el momento del diagnóstico, niveles altosde BCL-2 y bajo índice de proliferación con Ki-67. En cambio,los carcinomas de mama de tipo basal y HER2 presentabantumores de mayor tamaño, pobremente diferenciados, mayorcompromiso ganglionar y estadios más avanzados en elmomento del diagnóstico. Expresaban con mayor frecuenciaíndices de proliferación altos con Ki 67 y fueron los subtiposque en curvas de supervivencia global y de supervivencia librede progresión mostraron un peor pronóstico.Conclusión. La clasificación del cáncer de mama basada enparámetros inmunohistoquímicos (IHQ) permite una mejordefinición pronóstica. Tanto los carcinomas de mama detipo basal como HER2 presentan características histopatológicase IHQ más desfavorables así como peor supervivenciay menor tiempo de recaída mientras que los carcinomasde mama de tipo luminal manifiestan características másbenignas y mejor pronóstico(AU)

Background. Breast carcinomas are a heterogeneous groupof tumours, in both their clinical behavior and their prognosis.The aim of this article is to classify breast carcinomasaccording to molecular subtypes by means of immunohistochemicalmarkers and to analyse the clinicopathologicaland immunohistochemical characteristics and the patternsof survival and relapse of the different subtypes.Methods. Two hundred and seventy-two patients diagnosedwith breast cancer were classified into five subtypes: breastcarcinomas of the basal type, HER2 type, luminal A type,luminal B type and normal.Results. The most frequent breast carcinomas were: luminalA type carcinomas (62.5%), luminal B type carcinomas(18%), HER2 type carcinomas (9.9%), basal type carcinomas(8.4%) and normal phenotype carcinomas (1.4%). Significantlyand with greater frequency, the luminal type breastcarcinomas proved to be well differentiated tumours, ofsmall tumoral size, with negative axillary lymph nodes, at anearly stage at the time of diagnosis, with high levels of BCL-2 and a low Ki-67 proliferation index. On the contrary, thebasal type and HER2 carcinomas presented larger tumours,poorly differentiated, greater ganglionar involvement andmore advanced stages at the time of diagnosis. They expressedhigh Ki-67 proliferation indexes with greater frequencyand were the subtypes that showed a worse prognosis onglobal survival and progression-free survival curves.Conclusion. Breast cancer classification based on immunohistochemical(IHC) parameters makes a better prognosticdefinition possible. Both the basal type and the HER2 typebreast carcinomas present more unfavourable histopathologicaland IHC characteristics, as well as a worse survivaland less relapse time, while the luminal type breast carcinomasshow more benign characteristics and a better prognosis(AU)