Patient-derived tumor organoids with p53 mutations, and not wild-type p53, are sensitive to synergistic combination PARP inhibitor treatment.

Poly (ADP-ribose) polymerase inhibitors (PARPi) are used for patients with BRCA1/2 mutations, but patients with other mutations may benefit from PARPi treatment. Another mutation that is present in more cancers than BRCA1/2 is mutation to the TP53 gene. In 2D breast cancer cell lines, mutant p53 (mtp53) proteins tightly associate with replicating DNA and Poly (ADP-ribose) polymerase (PARP) protein. Combination drug treatment with the alkylating agent temozolomide and the PARPi talazoparib kills mtp53 expressing 2D grown breast cancer cell lines. We evaluated the sensitivity to the combination of temozolomide plus PARPi talazoparib treatment to breast and lung cancer patient-derived tumor organoids (PDTOs). The combination of the two drugs was synergistic for a cytotoxic response in PDTOs with mtp53 but not for PDTOs with wtp53. The combination of talazoparib and temozolomide induced more DNA double-strand breaks in mtp53 expressing organoids than in wild-type p53 expressing organoids as shown by increased γ-H2AX protein expression. Moreover, breast cancer tissue microarrays (TMAs) showed a positive correlation between stable p53 and high PARP1 expression in sub-groups of breast cancers, which may indicate sub-classes of breast cancers sensitive to PARPi therapy. These results suggest that mtp53 could be a biomarker to predict response to the combination of PARPi talazoparib-temozolomide treatment.

Patient-derived tumor organoids with p53 mutations, and not wild-type p53, are sensitive to synergistic combination PARP inhibitor treatment.

Poly (ADP-ribose) polymerase inhibitors (PARPi) are used for patients with BRCA1/2 mutations, but patients with other mutations may benefit from PARPi treatment. Another mutation that is present in more cancers than BRCA1/2 is mutation to the TP53 gene. In 2D breast cancer cell lines, mutant p53 (mtp53) proteins tightly associate with replicating DNA and Poly (ADP-ribose) polymerase (PARP) protein. Combination drug treatment with the alkylating agent temozolomide and the PARPi talazoparib kills mtp53 expressing 2D grown breast cancer cell lines. We evaluated the sensitivity to the combination of temozolomide plus PARPi talazoparib treatment to breast and lung cancer patient-derived tumor organoids (PDTOs). The combination of the two drugs was synergistic for a cytotoxic response in PDTOs with mtp53 but not for PDTOs with wtp53. The combination of talazoparib and temozolomide induced more DNA double-strand breaks in mtp53 expressing organoids than in wild-type p53 expressing organoids as shown by increased γ-H2AX protein expression. Moreover, breast cancer tissue microarrays (TMAs) showed a positive correlation between stable p53 and high PARP1 expression in sub-groups of breast cancers, which may indicate sub-classes of breast cancers sensitive to PARPi therapy. These results suggest that mtp53 could be a biomarker to predict response to the combination of PARPi talazoparib-temozolomide treatment.

African Ancestry-Associated Gene Expression Profiles in Triple-Negative Breast Cancer Underlie Altered Tumor Biology and Clinical Outcome in Women of African Descent.

Women of sub-Saharan African descent have disproportionately higher incidence of triple-negative breast cancer (TNBC) and TNBC-specific mortality across all populations. Population studies show racial differences in TNBC biology, including higher prevalence of basal-like and quadruple-negative subtypes in African Americans (AA). However, previous investigations relied on self-reported race (SRR) of primarily U.S. populations. Due to heterogeneous genetic admixture and biological consequences of social determinants, the true association of African ancestry with TNBC biology is unclear. To address this, we conducted RNA sequencing on an international cohort of AAs, as well as West and East Africans with TNBC. Using comprehensive genetic ancestry estimation in this African-enriched cohort, we found expression of 613 genes associated with African ancestry and 2,000+ associated with regional African ancestry. A subset of African-associated genes also showed differences in normal breast tissue. Pathway enrichment and deconvolution of tumor cellular composition revealed that tumor-associated immunologic profiles are distinct in patients of African descent. SIGNIFICANCE: Our comprehensive ancestry quantification process revealed that ancestry-associated gene expression profiles in TNBC include population-level distinctions in immunologic landscapes. These differences may explain some differences in race-group clinical outcomes. This study shows the first definitive link between African ancestry and the TNBC immunologic landscape, from an African-enriched international multiethnic cohort. See related commentary by Hamilton et al., p. 2496. This article is highlighted in the In This Issue feature, p. 2483.

Investigation of triple-negative breast cancer risk alleles in an International African-enriched cohort.

Large-scale efforts to identify breast cancer (BC) risk alleles have historically taken place among women of European ancestry. Recently, there are new efforts to verify if these alleles increase risk in African American (AA) women as well. We investigated the effect of previously reported AA breast cancer and triple-negative breast cancer (TNBC) risk alleles in our African-enriched International Center for the Study of Breast Cancer Subtypes (ICSBCS) cohort. Using case-control, case-series and race-nested approaches, we report that the Duffy-null allele (rs2814778) is associated with TNBC risk (OR = 3.814, p = 0.001), specifically among AA individuals, after adjusting for self-indicated race and west African ancestry (OR = 3.368, p = 0.007). We have also validated the protective effect of the minor allele of the ANKLE1 missense variant rs2363956 among AA for TNBC (OR = 0.420, p = 0.005). Our results suggest that an ancestry-specific Duffy-null allele and differential prevalence of a polymorphic gene variant of ANKLE1 may play a role in TNBC breast cancer outcomes. These findings present opportunities for therapeutic potential and future studies to address race-specific differences in TNBC risk and disease outcome.

Breast Cancer in Ghana: Demonstrating the Need for Population-Based Cancer Registries in Low- and Middle-Income Countries.

Purpose Breast cancer, the most common cancer worldwide, is the leading cause of cancer mortality in Ghanaian women. Previous studies find Ghanaian women are diagnosed at a younger age and at more advanced stages (III and IV), and have tumors with characteristics similar to African American women. We sought to remedy gaps in knowledge about breast cancer survival in Ghana and its relation to demographic and biologic factors of the tumors at diagnosis to assist in cancer control and registration planning. Methods Individuals with a breast cancer diagnosis who sought care at Komfo Anokye Teaching Hospital from 2009 to 2014 were identified via medical records. Follow-up telephone interviews were held to assess survival. Kaplan-Meier plots and Cox proportional hazards models assessed survival associated with clinical and demographic characteristics. Results A total of 223 patients completed follow-up and were analyzed. The median survival was 3.8 years. Approximately 50% of patients were diagnosed with grade 3 tumors, which significantly increased the risk of recurrence or death (hazard ratio [HR] for grade 2 versus 1, 2.98; 95% CI, 1.26 to 7.02; HR grade 3 v 1, 2.56; 95% CI, 1.08 to 6.07; P = .04). No other variables were significantly associated with survival. Conclusion Higher tumor grade was significantly associated with shorter survival, indicating impact of aggressive biology at diagnosis on higher risk of cancer spread and recurrence. Contrary to prevailing notions, telephone numbers were not reliable for follow-up. Collecting additional contact information will likely contribute to improvements in patient care and tracking. A region-wide population-based active registry is important to implement cancer control programs and improve survival in sub-Saharan Africa.

Hormone receptors and Her2 expression in breast cancer in sub-Saharan Africa. A comparative study of biopsies from Ghana and Norway.

Hormonal treatment of breast cancer is effective only in patients whose tumors express estrogen and/or progesterone receptors (ER, PR). Receptor assessment is often not available in low-resource areas, and the choice may be to apply endocrine therapy to all or none of breast cancer patients, depending on the proportion of patients that can be expected to respond. Fifty-one invasive breast cancers from Ghana and 100 from Norway diagnosed in the same laboratory during the same time period were reexamined in a blinded slide review. Of Ghanaian tumors, 76% were ER+ (≥1% ER+ tumor cells). Of Norwegian tumors, 85% were ER+. Triple-negative tumors were seen in 22% of Ghanaian patients and in 7% of Norwegian patients. A review of previous similar studies in sub-Saharan patients shows very discrepant results. Standardization and quality control of receptor assessment and well-designed clinical trials in sub-Saharan African breast cancer patients are needed to give a sound basis for endocrine treatment in this area.