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

Aberrant p53 immunostaining patterns in breast carcinoma of no special type strongly correlate with presence and type of TP53 mutations

Recent studies have revealed an association between TP53 mutations and endocrine resistance in hormone receptor-positive, HER2-negative breast cancer (HR + HER2 -BC). Aberrant p53 immunostaining (IHC) patterns may provide a surrogate marker for TP53 mutations. Building upon a ternary algorithm of aberrant staining patterns, this study evaluates the reliability of p53 IHC as screening tool for TP53 mutations in BC (NST). Furthermore, it describes the histopathological and molecular characteristics of TP53-mutated cases, along with the mutational status of PIK3CA. This study comprised 131 early-stage, node-negative BCs with available core biopsies and resection specimens. Cases were categorized as follows: HR + HER2 - (85 cases), HER2 + (21 cases) and triple negative (TN, 25 cases). Aberrant IHC staining patterns for p53 were defined as overexpression (OE), complete absence (CA) and cytoplasmic (CY). In addition, targeted sequencing of TP53 and PIK3CA genes was performed. TP53 mutations were identified in 53 of 126 cases (42.1%). Within HR + HER2 - cases, TP53 mutations were found in 17 of 80 cases (21.3%). IHC accurately predicted TP53 mutation in 96.2% of cases with a specificity of 100%. Additionally, there was a significant agreement between missense mutations and OE, as well as between truncating mutations and CA (κ 73% and 76%). CY was observed in two TN cases with truncating mutations within the nuclear localization signalling domain of p53. TP53-mutated cases exhibited higher grade, greater nuclear pleomorphism and higher Ki-67 proliferation index and were associated with the PIK3CA wild-type status (p < 0.001). p53 IHC may provide a useful screening tool for identifying TP53-mutated BC of NST.

TP53-associated early breast cancer: new observations from a large cohort

BACKGROUND

A recent large, well-annotated international cohort of patients with Li-Fraumeni syndrome and early-stage breast cancer was examined for shared features.

METHODS

This multicenter cohort study included women with a germline TP53 pathogenic or likely pathogenic variant and nonmetastatic breast cancer diagnosed between 2002 and 2022. Clinical and genetic data were obtained from institutional registries and clinical charts. Descriptive statistics were used to summarize proportions, and differences were assessed using χ2 or Wilcoxon rank sum tests. Metachronous contralateral breast cancer risk, radiation-induced sarcoma risk, and recurrence-free survival were analyzed using the Kaplan-Meier methodology.

RESULTS

Among 227 women who met study criteria, the median age of first breast cancer diagnosis was 37 years (range = 21-71), 11.9% presented with bilateral synchronous breast cancer, and 18.1% had ductal carcinoma in situ only. In total, 166 (73.1%) patients underwent mastectomies, including 67 bilateral mastectomies as first breast cancer surgery. Among those patients with retained breast tissue, the contralateral breast cancer rate was 25.3% at 5 years. Among 186 invasive tumors, 72.1% were stages I to II, 48.9% were node negative, and the most common subtypes were hormone receptor-positive/HER2-negative (40.9%) and hormone receptor positive/HER2 positive (34.4%). At a median follow-up of 69.9 months (interquartile range = 32.6-125.9), invasive hormone receptor-positive/HER2-negative disease had the highest recurrence risk among the subtypes (5-year recurrence-free survival = 61.1%, P = .001). Among those who received radiation therapy (n = 79), the 5-year radiation-induced sarcoma rate was 4.8%.

CONCLUSION

We observed high rates of ductal carcinoma in situ, hormone receptor-positive, and HER2-positive breast cancers, with a worse outcome in the hormone receptor-positive/HER2-negative luminal tumors, despite appropriate treatment. Confirmation of these findings in further studies could have implications for breast cancer care in those with Li-Fraumeni syndrome.

p53R172H and p53R245W Hotspot Mutations Drive Distinct Transcriptomes in Mouse Mammary Tumors Through a Convergent Transcriptional Mediator

Aggressive breast cancers harbor TP53 missense mutations. Tumor cells with TP53 missense mutations exhibit enhanced growth and survival through transcriptional rewiring. To delineate how TP53 mutations in breast cancer contribute to tumorigenesis and progression in vivo, we created a somatic mouse model driven by mammary epithelial cell-specific expression of Trp53 mutations. Mice developed primary mammary tumors reflecting the human molecular subtypes of luminal A, luminal B, HER2-enriched, and triple-negative breast cancer with metastases. Transcriptomic analyses comparing MaPR172H/- or MaPR245W/- mammary tumors to MaP-/- tumors revealed (1) differences in cancer-associated pathways activated in both p53 mutants and (2) Nr5a2 as a novel transcriptional mediator of distinct pathways in p53 mutants. Meta-analyses of human breast tumors corroborated these results. In vitro assays demonstrate mutant p53 upregulates specific target genes that are enriched for Nr5a2 response elements in their promoters. Co-immunoprecipitation studies revealed p53R172H and p53R245W interact with Nr5a2. These findings implicate NR5A2 as a novel mediator of mutant p53 transcriptional activity in breast cancer.

SIGNIFICANCE

Our findings implicate NR5A2 as a novel mediator of mutant p53 transcriptional activity in breast cancer. NR5A2 may be an important therapeutic target in hard-to-treat breast cancers such as endocrine-resistant tumors and metastatic triple-negative breast cancers harboring TP53 missense mutations.

Interplay between Wnt signaling molecules and exosomal miRNAs in breast cancer (Review)

Breast cancer (BC) is the most common malignancy in women worldwide. Wnt signaling is involved in tumorigenesis and cancer progression, and is closely associated with the characteristics of BC. Variation in the expression of exosomal microRNAs (miRNAs) modulates key cancer phenotypes, such as cellular proliferation, epithelial‑mesenchymal transition, metastatic potential, immune evasion and treatment resistance. The present review aimed to discuss the importance of Wnt signaling and exosomal miRNAs in regulating the occurrence and development of BC. In addition, the present review determined the crosstalk between Wnt signaling and exosomal miRNAs, and highlighted potential diagnostic biomarkers and therapeutic targets.

Integration of Pathological Criteria and Immunohistochemical Evaluation for Invasive Lobular Carcinoma Diagnosis: Recommendations From the European Lobular Breast Cancer Consortium

Invasive lobular carcinoma (ILC) is the second most frequent type of breast cancer (BC) and its peculiar morphology is mainly driven by inactivation of CDH1, the gene coding for E-cadherin cell adhesion protein. ILC-specific therapeutic and disease-monitoring approaches are gaining momentum in the clinic, increasing the importance of accurate ILC diagnosis. Several essential and desirable morphologic diagnostic criteria are currently defined by the World Health Organization, the routine use of immunohistochemistry (IHC) for E-cadherin is not recommended. Disagreement in the diagnosis of ILC has been repeatedly reported, but interpathologist agreement increases with the use of E-cadherin IHC. In this study, we aimed to harmonize the pathological diagnosis of ILC by comparing 5 commonly used E-cadherin antibody clones (NCH-38, EP700Y, Clone 36, NCL-L-E-cad [Clone 36B5], and ECH-6). We determined their biochemical specificity for the E-cadherin protein and IHC staining performance according to type and location of mutation on the CDH1 gene. Western blot analysis on mouse cell lines with conditional E-cadherin expression revealed a reduced specificity of EP700Y and NCL-L-E-cad for E-cadherin, with cross-reactivity of Clone 36 to P-cadherin. The use of IHC improved interpathologist agreement for ILC, lobular carcinoma in situ, and atypical lobular hyperplasia. The E-cadherin IHC staining pattern was associated with variant allele frequency and likelihood of nonsense-mediated RNA decay but not with the type or position of CDH1 mutations. Based on these results, we recommend the indication for E-cadherin staining, choice of antibodies, and their interpretation to standardize ILC diagnosis in current pathology practice.

Frequency of genetic alterations differs in advanced breast cancer between metastatic sites

About 20%-30% of breast cancer (BC) patients will develop distant metastases, preferentially in bones, liver, lung, and brain. BCs with different intrinsic subtypes prefer different sites for metastasis. These subtypes vary in the abundance of genetic alterations which may influence the localization of metastases. Currently, information about the relation between metastatic site and mutational profile of BC is limited. In this study, n = 521 BC metastases of the most frequently affected sites (bone, brain, liver, and lung) were investigated for the frequency of AKT1, ERBB2, ESR1, PIK3CA, and TP53 mutations via NGS and pyrosequencing. Somatic mutations were present in 64% cases. PIK3CA and TP53 were the most frequently mutated genes under study. We provide an analysis of the mutational profile of BCs and the affected metastatic site. Genetic alterations differed significantly depending on the organ site affected by metastases. TP53 mutations were mostly observed in brain metastases (51.0%), metastases outside of the brain revealed a much lower proportion of TP53 mutated samples. PIK3CA mutations are frequent in liver (40.6%), lung (36.8%), and bone metastases (35.7%), whereas less common in brain metastases (18.4%). The highest percentage of ESR1 mutations was observed in liver and lung metastases (about 30% each), whereas metastatic lesions in the brain showed significantly less ESR1 mutations, only in 2.0% of the cases. In summary, we found significant differences of mutational status in mBC depending on the affected organ and intrinsic subtype. Organotropism of metastatic cancer spread may be influenced by the mutational profile of individual BCs.

HER2-positive breast cancer progresses rapidly after pyrotinib resistance: acquired RET gene fusion and TP53 gene mutation are potential reasons

Approximately 15-20% of the patients with breast cancer overexpress human epidermal growth factor receptor 2 ( HER2 ). HER2 -positive breast cancer is highly aggressive and has a high relapse rate, suggesting that it is prone to and progresses rapidly after drug resistance. Pyrotinib resistance and changes in patients' conditions after drug resistance are challenging clinical issues and require medical attention. Recently, there are few clinical reports on changes in patients' conditions after pyrotinib resistance. We report a case of a 46-year-old patient with HER2 -positive breast cancer who developed resistance to pyrotinib and rapidly progressed to uncontrolled liver failure in less than a week. To elucidate the cause of the rapid progression, we collected samples of the patient's ascites and performed next-generation sequencing (NGS). On the basis of the NGS results, we speculated that the rapid progression after pyrotinib resistance might be due to RET gene fusion and TP53 gene mutations. Therefore, this case report aims to alert oncologists that patients with HER2 -positive breast cancer, who are resistant to pyrotinib or other targeted drugs, could experience rapid or even flare-up progression and that RET gene fusion and TP53 gene mutations might be potential causes.

Evaluation of the routine use of E-cadherin immunohistochemistry in the typing of breast carcinomas: results of a randomized diagnostic study

AIMS

Invasive lobular carcinoma (ILC) has distinct morphology and association with loss of E-cadherin function. It has special clinical and imaging features, and its proper recognition is important. Following a recent proposal, we tested the value of the routine use of E-cadherin immunohistochemistry (IHC) in recognizing ILC.

METHODS AND RESULTS

Five pathologists with experience in breast pathology from four Hungarian institutions histotyped 1001 breast cancers from diagnostic core biopsies or excision specimens randomly assigned to haematoxylin and eosin (HE) diagnosis first, followed by E-cadherin IHC; or to immediate HE and E-cadherin-based diagnosis. Of 524 cases with HE diagnosis, 73(14%) were deemed uncertain. E-cadherin made the initial histological type change in 14/524 cases (2.7%), including three with confident HE-based type allocation. Use of E-cadherin immunostaining was considered useful in 88/477 cases (18%) with immediate dual assessment, and typing uncertainty went down to 5% (25/477 cases), but was not zero. Collective assessment of 171 uncertain, difficult, nonclassical cases resulted in consensus diagnosis in most cases, but 15 cases were still doubtful as concerns their proper histological type. CDH1 gene sequencing was attempted and successful in 13; pathogenic genetic alterations were identified in seven cases.

CONCLUSIONS

The routine use of E-cadherin IHC decreases the uncertainty in typing and improves the typing accuracy at the cost of potentially redundant additional immunostains. Furthermore, this procedure does not exclude uncertainty due to E-cadherin-positive ILCs, which are occasionally difficult to confidently label as ILC, especially when the growth pattern is not classic.

Molecular profiling of aromatase inhibitor sensitive and resistant ER+HER2- postmenopausal breast cancers

Aromatase inhibitors (AIs) reduce recurrences and mortality in postmenopausal patients with oestrogen receptor positive (ER+) breast cancer (BC), but >20% of patients will eventually relapse. Given the limited understanding of intrinsic resistance in these tumours, here we conduct a large-scale molecular analysis to identify features that impact on the response of ER + HER2- BC to AI. We compare the 15% of poorest responders (PRs, n = 177) as measured by proportional Ki67 changes after 2 weeks of neoadjuvant AI to good responders (GRs, n = 190) selected from the top 50% responders in the POETIC trial and matched for baseline Ki67 categories. In this work, low ESR1 levels are associated with poor response, high proliferation, high expression of growth factor pathways and non-luminal subtypes. PRs having high ESR1 expression have similar proportions of luminal subtypes to GRs but lower plasma estradiol levels, lower expression of estrogen response genes, higher levels of tumor infiltrating lymphocytes and immune markers, and more TP53 mutations.

Molecular Profiling in Early ER + Breast Cancer to Aid Systemic Therapy Decisions

PURPOSE OF REVIEW

Clinical decisions for (neo)adjuvant treatment in early breast cancer (eBC) have been based mostly on clinical factors over the last decades. We have reviewed development and validation of such assays in the HR + /HER2 eBC and discuss possible future directions in this field.

RECENT FINDINGS

Increasing knowledge about the biology of hormone-sensitive eBC, based on the precise and reproducible multigene expression analysis, has led to a significant change in the treatment pathways and reduction of overtreatment in particular by chemotherapy in HR + /HER2 eBC with up to 3 positive lymph nodes based on results from several retrospective-prospective trials used several genomic assays and in particular prospective trials (TAILORx, RxPonder, MINDACT, and ADAPT used OncotypeDX® and Mammaprint®). Precise evaluation of tumor biology together with endocrine responsiveness assessment appears as promising tools for individualized treatment decisions together with clinical factors and menopausal status in early hormone-sensitive/HER2-negative breast cancer.

p53 Expression in Luminal Breast Cancer Correlates With TP53 Mutation and Primary Endocrine Resistance

TP53 mutation is associated with primary endocrine resistance in luminal breast cancer (BC). Nuclear accumulation of p53, as determined by immunohistochemistry (IHC), is a surrogate marker for TP53 mutation. The immunohistochemical p53 index that defines a p53-positive status is not well established. This study determined the optimal p53 index cutoff to identify luminal BCs harboring TP53 mutations. In total, 364 luminal BCs from the West German Study Group ADAPT trial (NCT01779206) were analyzed for TP53 mutations by next-generation sequencing and for p53 expression by IHC (DO-7 antibody). P53 indices were determined by automated image analysis. All tumors were from patients treated with short-term preoperative endocrine therapy (pET; tamoxifen or aromatase inhibitor) before tumor resection. IHC evaluation included needle biopsies before therapy (baseline) and resections specimens after therapy (post-pET). Optimal p53 index cutoffs were defined with Youden statistics. TP53 mutations were detected in 16.3% of BC cases. The median p53 indices were significantly higher in TP53-mutated BCs compared to BCs harboring wild-type TP53 (baseline: 47.0% vs 6.4%, P < .001; post-pET: 50.1% vs 1.1%, P < .001). Short-term pET decreased p53 indices in BCs harboring wild-type TP53 (P < .001) but not in TP53-mutated BCs (P = .102). For baseline biopsies, the optimal p53 index cutoff was ≥34.6% (specificity 0.92, sensitivity 0.63, Youden index 0.54, accuracy: 0.87). For post-pET specimens, the optimal cutoff was ≥25.3% (specificity 0.95, sensitivity 0.65, Youden index 0.60, accuracy: 0.90). Using these cutoffs to define the p53 status, p53-positive BCs were >2-fold more common in pET nonresponders compared to pET responders (baseline: 37/162, 22.8% vs 18/162, 11.1%, P = .007; post-pET: 36/179, 20.1% vs 16/179, 8.9%, P = .004). In summary, IHC for p53 identifies TP53-mutated luminal BCs with high specificity and accuracy. Optimal cutoffs are ≥35% and ≥25% for treatment-naïve and endocrine-pretreated patients, respectively.

Clinical validity and clinical utility of Ki67 in early breast cancer

Ki67 represents an immunohistochemical nuclear localized marker that is widely used in surgical pathology. Nuclear immunoreactivity for Ki67 indicates that cells are cycling and are in G1- to S-phase. The percentage of Ki67-positive tumor cells (Ki67 index) therefore provides an estimate of the growth fraction in tumor specimens. In breast cancer (BC), tumor cell proliferation rate is one of the most relevant prognostic markers and Ki67 is consequently helpful in prognostication similar to histological grading and mRNA profiling-based BC risk stratification. In BCs treated with short-term preoperative endocrine therapy, Ki67 dynamics enable distinguishing between endocrine sensitive and resistant tumors. Despite its nearly universal use in pathology laboratories worldwide, no internationally accepted consensus has yet been achieved for some methodological details related to Ki67 immunohistochemistry (IHC). Controversial issues refer to choice of IHC antibody clones, scoring methods, inter-laboratory reproducibility, and the potential value of computer-assisted imaging analysis and/or artificial intelligence for Ki67 assessment. Prospective clinical trials focusing on BC treatment have proven that Ki67, as determined by standardized central pathology assessment, is of clinical validity. Clinical utility has been demonstrated in huge observational studies.

[Predictive molecular diagnostics in breast cancer : What are the requirements for pathology today and in the future?]

With an increasing number of targeted therapy options for the treatment of solid tumors, the demands on predictive molecular diagnostics for pathology are growing. In breast cancer the need to determine genomic predictive markers for available targeted therapies has so far been manageable (detection of PIK3CA mutations in endocrine pretreated luminal tumors and the search for NTRK fusions indicated only in secretory breast cancer). At the latest in cases of nonresponse to first-line or second-line standard treatment, more comprehensive diagnostics using next generation sequencing (NGS) panel diagnostics makes sense. This should be suitable for clarifying resistance mechanisms, e.g. against endocrine therapy or cyclin-dependent kinase 4/cyclin-dependent kinase 6 (CDK4/6) inhibitors and to identify indications for therapies currently in development. The interpretation should be carried out in a quality assured manner in accordance with international standards and the interdisciplinary tumor board should make a transparent and standardized report available in a timely manner.

[Second opinions and reference pathology in breast cancer]

Second opinion in pathology recruits expert knowledge for the diagnosis in difficult cases and has a tradition in Germany with generation of a network between primarily diagnostic and academic institutes of pathology, active in research. The term reference pathology does mean a label for a class of institutes for pathology but rather specifies a function within prospective clinical trials with defined endpoints and a central pathology, which will derive expert knowledge from this function. On either way generated collection of samples and expertise will enable diagnostic support in difficult cases. Furthermore, research based on this tissue material might lead to the establishment of novel biomarkers and methods, which when transferred to decentral application will enhance diagnostic validity of pathological tissue analysis as a whole. Thus, for all institutes participating in the network, pathology as a diagnostic discipline and patients, second opinion and reference pathology provide considerable benefit with regard to quality of histopathological diagnoses.

Mutual exclusivity of ESR1 and TP53 mutations in endocrine resistant metastatic breast cancer

Both TP53 and ESR1 mutations occur frequently in estrogen receptor positive (ER+) metastatic breast cancers (MBC) and their distinct roles in breast cancer tumorigenesis and progression are well appreciated. Recent clinical studies discovered mutual exclusivity between TP53 and ESR1 mutations in metastatic breast cancers; however, mechanisms underlying this intriguing clinical observation remain largely understudied and unknown. Here, we explored the interplay between TP53 and ESR1 mutations using publicly available clinical and experimental data sets. We first confirmed the robust mutational exclusivity using six independent cohorts with 1,056 ER+ MBC samples and found that the exclusivity broadly applies to all ER+ breast tumors regardless of their clinical and distinct mutational features. ESR1 mutant tumors do not exhibit differential p53 pathway activity, whereas we identified attenuated ER activity and expression in TP53 mutant tumors, driven by a p53-associated E2 response gene signature. Further, 81% of these p53-associated E2 response genes are either direct targets of wild-type (WT) p53-regulated transactivation or are mutant p53-associated microRNAs, representing bimodal mechanisms of ER suppression. Lastly, we analyzed the very rare cases with co-occurrences of TP53 and ESR1 mutations and found that their simultaneous presence was also associated with reduced ER activity. In addition, tumors with dual mutations showed higher levels of total and PD-L1 positive macrophages. In summary, our study utilized multiple publicly available sources to explore the mechanism underlying the mutual exclusivity between ESR1 and TP53 mutations, providing further insights and testable hypotheses of the molecular interplay between these two pivotal genes in ER+ MBC.

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 <10%) versus slightly, moderately, and severely impaired (post‐pET Ki67 10%–19%, 20%–34%, and ≥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.