Microenvironment‐induced restoration of cohesive growth associated with focal activation of P ‐cadherin expression in lobular breast carcinoma metastatic to the colon

Invasive lobular carcinoma (ILC) is a special breast cancer type characterized by noncohesive growth and E‐cadherin loss. Focal activation of P‐cadherin expression in tumor cells that are deficient for E‐cadherin occurs in a subset of ILCs. Switching from an E‐cadherin deficient to P‐cadherin proficient status (EPS) partially restores cell–cell adhesion leading to the formation of cohesive tubular elements. It is unknown what conditions control EPS. Here, we report on EPS in ILC metastases in the large bowel. We reviewed endoscopic colon biopsies and colectomy specimens from a 52‐year‐old female (index patient) and of 18 additional patients (reference series) diagnosed with metastatic ILC in the colon. EPS was assessed by immunohistochemistry for E‐cadherin and P‐cadherin. CDH1 /E‐cadherin mutations were determined by next‐generation sequencing. The index patient's colectomy showed transmural metastatic ILC harboring a CDH1 /E‐cadherin p.Q610* mutation. ILC cells displayed different growth patterns in different anatomic layers of the colon wall. In the tunica muscularis propria and the tela submucosa, ILC cells featured noncohesive growth and were E‐cadherin‐negative and P‐cadherin‐negative. However, ILC cells invading the mucosa formed cohesive tubular elements in the intercryptal stroma of the lamina propria mucosae. Inter‐cryptal ILC cells switched to a P‐cadherin‐positive phenotype in this microenvironmental niche. In the reference series, colon mucosa infiltration was evident in 13 of 18 patients, one of which showed intercryptal EPS and conversion to cohesive growth as described in the index patient. The large bowel is a common metastatic site in ILC. In endoscopic colon biopsies, the typical noncohesive growth of ILC may be concealed by microenvironment‐induced EPS and conversion to cohesive growth

Microenvironment-induced restoration of cohesive growth associated with focal activation of P-cadherin expression in lobular breast carcinoma metastatic to the colon

Invasive lobular carcinoma (ILC) is a special breast cancer type characterized by noncohesive growth and E-cadherin loss. Focal activation of P-cadherin expression in tumor cells that are deficient for E-cadherin occurs in a subset of ILCs. Switching from an E-cadherin deficient to P-cadherin proficient status (EPS) partially restores cell–cell adhesion leading to the formation of cohesive tubular elements. It is unknown what conditions control EPS. Here, we report on EPS in ILC metastases in the large bowel. We reviewed endoscopic colon biopsies and colectomy specimens from a 52-year-old female (index patient) and of 18 additional patients (reference series) diagnosed with metastatic ILC in the colon. EPS was assessed by immunohistochemistry for E-cadherin and P-cadherin. CDH1/E-cadherin mutations were determined by next-generation sequencing. The index patient's colectomy showed transmural metastatic ILC harboring a CDH1/E-cadherin p.Q610* mutation. ILC cells displayed different growth patterns in different anatomic layers of the colon wall. In the tunica muscularis propria and the tela submucosa, ILC cells featured noncohesive growth and were E-cadherin-negative and P-cadherin-negative. However, ILC cells invading the mucosa formed cohesive tubular elements in the intercryptal stroma of the lamina propria mucosae. Inter-cryptal ILC cells switched to a P-cadherin-positive phenotype in this microenvironmental niche. In the reference series, colon mucosa infiltration was evident in 13 of 18 patients, one of which showed intercryptal EPS and conversion to cohesive growth as described in the index patient. The large bowel is a common metastatic site in ILC. In endoscopic colon biopsies, the typical noncohesive growth of ILC may be concealed by microenvironment-induced EPS and conversion to cohesive growth

ERBB2 mutation is associated with sustained tumor cell proliferation after short-term preoperative endocrine therapy in early lobular breast cancer

Invasive lobular breast cancer (ILC) is a special breast cancer (BC) subtype and is mostly hormone receptor (HR)-positive and ERBB2 non-amplified. Endocrine therapy restrains tumor proliferation and is the mainstay of lobular BC treatment. Mutation of ERBB2 has been associated with recurrent ILC. However, it is unknown whether ERBB2 mutation impacts on the otherwise exquisite responsiveness of early ILC to endocrine therapy. We have recently profiled n = 622 HR-positive early BCs from the ADAPT trial for mutations in candidate genes involved in endocrine resistance, including ERBB2. All patients were treated with short-term preoperative endocrine therapy (pET, tamoxifen or aromatase inhibitors) before tumor resection. Tumor proliferation after endocrine therapy (post-pET Ki67 index) was determined prospectively by standardized central pathology assessment supported by computer-assisted image analysis. Sustained or suppressed proliferation were defined as post-pET Ki67 =10% or <10%. Here, we report a subgroup analysis pertaining to ILCs in this cohort. ILCs accounted for 179/622 (28.8%) cases. ILCs were enriched in mutations in CDH1 (124/179, 69.3%, P < 0.0001) and ERBB2 (14/179, 7.8%, P < 0.0001), but showed fewer mutations in TP53 (7/179, 3.9%, P = 0.0048) and GATA3 (11/179, 6.1%, P < 0.0001). Considering all BCs irrespective of subtypes, ERBB2 mutation was not associated with proliferation. In ILCs, however, ERBB2 mutations were 3.5-fold more common in cases with sustained post-pET proliferation compared to cases with suppressed post-pET proliferation (10/75, 13.3% versus 4/104, 3.8%, P = 0.0248). Moreover, ERBB2 mutation was associated with high Oncotype DX recurrence scores (P = 0.0087). In summary, our findings support that ERBB2 mutation influences endocrine responsiveness in early lobular BC

TP53 mutations are associated with primary endocrine resistance in luminal early breast cancer

Background Whereas the genomic landscape of endocrine-resistant breast cancer has been intensely characterized in previously treated cases with local or distant recurrence, comparably little is known about genomic alterations conveying primary non-responsiveness to endocrine treatment in luminal early breast cancer. Methods In this study, 622 estrogen receptor-expressing breast cancer cases treated with short-term preoperative endocrine therapy (pET) from the WSG-ADAPT trial (NCT01779206) were analyzed for genetic alterations associated with impaired endocrine proliferative response (EPR) to 3-week pET with tamoxifen or aromatase inhibitors. EPR was categorized as optimal (post-pET Ki67 = 35%, respectively). Recently described gene mutations frequently found in previously treated advanced breast cancer were analyzed (ARID1A, BRAF, ERBB2, ESR1, GATA3, HRAS, KRAS, NRAS, PIK3CA, and TP53) by next-generation sequencing. Amplifications of CCND1, FGFR1, ERBB2, and PAK1 were determined by digital PCR or fluorescence in situ hybridization. Results ERBB2 amplification (p = 0.0015) and mutations of TP53 (p < 0.0001) were significantly associated with impaired EPR. Impaired EPR in TP53-mutated breast cancer cases was independent from the Oncotype DX Recurrence Score group and was seen both with tamoxifen- and aromatase inhibitor-based pET (p = 0.0005 each). Conclusion We conclude that impaired EPR to pET is suitable to identify cases with primary endocrine resistance in early luminal breast cancer and that TP53-mutated luminal cancers might not be sufficiently treated by endocrine therapy alone

Microenvironment‐induced restoration of cohesive growth associated with focal activation of P‐cadherin expression in lobular breast carcinoma metastatic to the colon

Abstract Invasive lobular carcinoma (ILC) is a special breast cancer type characterized by noncohesive growth and E‐cadherin loss. Focal activation of P‐cadherin expression in tumor cells that are deficient for E‐cadherin occurs in a subset of ILCs. Switching from an E‐cadherin deficient to P‐cadherin proficient status (EPS) partially restores cell–cell adhesion leading to the formation of cohesive tubular elements. It is unknown what conditions control EPS. Here, we report on EPS in ILC metastases in the large bowel. We reviewed endoscopic colon biopsies and colectomy specimens from a 52‐year‐old female (index patient) and of 18 additional patients (reference series) diagnosed with metastatic ILC in the colon. EPS was assessed by immunohistochemistry for E‐cadherin and P‐cadherin. CDH1/E‐cadherin mutations were determined by next‐generation sequencing. The index patient's colectomy showed transmural metastatic ILC harboring a CDH1/E‐cadherin p.Q610* mutation. ILC cells displayed different growth patterns in different anatomic layers of the colon wall. In the tunica muscularis propria and the tela submucosa, ILC cells featured noncohesive growth and were E‐cadherin‐negative and P‐cadherin‐negative. However, ILC cells invading the mucosa formed cohesive tubular elements in the intercryptal stroma of the lamina propria mucosae. Inter‐cryptal ILC cells switched to a P‐cadherin‐positive phenotype in this microenvironmental niche. In the reference series, colon mucosa infiltration was evident in 13 of 18 patients, one of which showed intercryptal EPS and conversion to cohesive growth as described in the index patient. The large bowel is a common metastatic site in ILC. In endoscopic colon biopsies, the typical noncohesive growth of ILC may be concealed by microenvironment‐induced EPS and conversion to cohesive growth