Statistical association of basal cell keratins with metastasis-inducing proteins in a prognostically unfavorable group of sporadic breast cancers

Abstract

Two subgroups of invasive breast carcinomas have been identified with a poor prognosis in different patient cohorts: the basal-like category and the subgroup containing proteins capable of inducing metastasis in experimental rodents, the metastasis-inducing proteins (MIPs). Here we identify by immunohistochemical staining for cytokeratin CK5/6 or CK14 the basal-like subgroup in a set of 297 primary invasive breast carcinomas in which the staining profile for the MIPs S100A4, osteopontin, anterior gradient-2, and S100P has already been established. Monoclonal antibodies to CK5/6 or CK14 specifically stain 31% to 34% of the primary carcinomas. These positively stained tumors are highly significantly associated with premature death of the patient (Wilcoxon statistics, P < 0.0001), the increased relative risk being approximately 5.6-fold. Positive staining for either cytokeratin is very significantly associated with that for each of the four MIPs separately and with loss of staining for the Fanconi anemia protein FANCD2 (corrected Fisher's exact test, P < 0.0007). There is no significant correlation with the remaining tumor variables tested, including staining for the estrogen receptor α, progesterone receptor, and c-erbB-2. These results show that the basal cytokeratin-like carcinomas contain many of the MIPs and that these may arise by their selection for tumors with an inherent deficiency in the FANC/BRCA pathway of DNA repair.

Figure 1

IHC staining of human breast tissues for cytokeratins CK14 and CK5/6. A: Incubation of normal breast duct tissue with antibody to CK14 shows staining of myoepithelial/basal cells (arrowheads) and of occasional suprabasal epithelial-like cells (arrows); most epithelial cells (e) and the adjacent stromal cells (s) were unstained. B: Invasive carcinoma stained for CK5/6 shows no IHC staining. C: Invasive carcinoma stained for CK5/6 shows borderline staining of the occasional malignant cell (arrow). D: Invasive carcinoma stained for CK5/6 shows positive staining for malignant cells. E: Invasive carcinoma stained for CK14 shows positive staining for malignant cells (arrow); host fibroblasts and blood vessels were unstained (arrowheads). F: A different section of the invasive carcinoma in E, at a higher magnification, illustrates cytoplasmic staining (arrows) in malignant cells stained for CK14. G and H: Adjacent sections of the same invasive carcinoma. Tissue incubated with mAb to CK14 (G) shows strong staining of the carcinoma cells; there is no staining with the same mAb preincubated with our synthetic peptide (described under Materials and Methods) (H); necrotic areas (n) were unstained under both conditions. Original magnification: ×400 (B, C, and E); ×500 (D, G, and H); ×620 (A and F). Scale bars = 25 μm.

Figure 2

Association of IHC staining for cytokeratins CK5/6 and CK14 with overall duration of patient survival. A: The cumulative proportion of surviving patients as a percentage of the total for each year after presentation for patients with carcinomas classified as unstained (set a, solid line) or positively stained (set b, dotted line) for CK5/6. There were 154 censored observations in set a (53 dead of other causes) and 12 in set b (three dead of other causes). The two curves were highly significantly different (Wilcoxon statistic χ² = 72.81, 1 df, P < 0.0001). B: The cumulative proportion of surviving patients with carcinomas classified as unstained (set a, solid line) or positively stained (set b, dotted line) for CK14. There were 149 censored observations in set a (48 dead of other causes) and 17 in set b (eight dead of other causes). The two curves were highly significantly different (Wilcoxon statistic χ² = 78.63, 1 df, P < 0.0001).