Association of ERα-36 expression with the de novo resistance of tamoxifen in ER-positive breast cancer

BACKGROUND: Approximately 70–80% of breast cancer express ER-alpha and hormonal therapies, given significant improvements in patient survival. About 50% of ER-positive breast cancer patients with advanced disease insensitive to tamoxifen treatment when diagnosed. Recent studies have shown that ERα-36 is a crucial factor in the resistance of tamoxifen. OBJECTIVE: This study aims to determine the association between ERα-36 expression and de novo resistance of tamoxifen in patients with ER-positive breast cancer. METHODS: This study was an observational study using a cross-sectional method and was conducted at Wahidin Sudirohusodo Hospital and Unhas Hospital. ERα-36 protein expression was assessed using an immunohistochemistry assay. The association of ERα-36 expression and resistance of tamoxifen was tested with the Chi-square test. RESULTS: A total of 50 locally advanced breast cancer cases were included in this study, 22 cases (44%) had overexpression of ERα-36, and 28 cases (56%) had not, 24 cases (48%) had experience resistance to tamoxifen and 26 cases (52%) had not. There was a significant association between ERα-36 expressions and resistance of tamoxifen (p = 0.000). CONCLUSIONS: There was an association between the expression of ER-α36 with de novo resistance of tamoxifen in ER-positive breast cancer. ER-α36 could act as a worth considering biomarker for de novo resistance of tamoxifen in therapeutic strategies.

Whole-exome sequencing in advanced-stage sensitizing EGFR mutation non-small cell lung cancer: Explore resistance biomarkers to EGFR TKI treatment.

9039 Background: Despite the development of predictive biomarkers to shape treatment paradigms and outcomes, 10-20% of de novo EGFR TKI resistance advanced non-small cell lung cancer (NSCLC) in the presence of EGFR mutation remains the issue of concern. Methods: We explored clinical factors in 332 advanced NSCLC who received EGFR TKI and molecular characteristics through 65 whole exome sequencing of various EGFR TKI responses including; de novo (progression within 3 months), intermediate response (IRs) and long-term response (LTRs) (durability > 2 year). Results: Uncommon EGFR mutation subtype was a significant variable in de novo resistance vs. IRs and LTRs with odd ratios of 6.83 ([95% CI 2.36 – 19.80], p-value < 0.001) and 16.84 ([95%CI 1.66 – 171.45, p-value 0.02), respectively. The remaining sensitizing EGFR mutation subtype (exon 19 del and L858R) accounted for 75% of de novo resistance. Genomic landscape analysis was conducted, focusing in 10 frequent oncogenic signaling pathways with functional contributions; cell cycle, Hippo, Myc, Notch, Nrf2, PI-3-Kinase/Akt, RTK-RAS, TGF-β, p53 and β-catenin/Wnt signaling. Cell cycle pathway was the only significant alteration pathway among groups with the FDR p-value of 6×10-4. We found only significant q-values of < 0.05 in 7 gene alterations; CDK6, CCNE1, CDK4, CCND3, MET, FGFR4 and HRAS which enrich in de novo resistance [range 36-73%] compared to IRs/LTRs [range 4-22%]. Amplification of CDK4/6 was significant in de novo resistance, contrary to IRs and LTRs (91%, 27.9% and 0%, respectively). The presence of co-occurrence CDK4 /6 amplification correlated with poor disease outcome with HR of progression-free survival of 3.63 [95% CI 1.80-7.31, p-value < 0.001]. Conclusions: The presence of CDK4 /6 amplification in pretreatment specimen serve as a predictive biomarker for de novo resistance in sensitizing EGFR mutation.

Expanded and activated allogeneic NK cells are cytotoxic against B-chronic lymphocytic leukemia (B-CLL) cells with sporadic cases of resistance

Adoptive transfer of allogeneic natural killer (NK) cells is becoming a credible immunotherapy for hematological malignancies. In the present work, using an optimized expansion/activation protocol of human NK cells, we generate expanded NK cells (eNK) with increased expression of CD56 and NKp44, while maintaining that of CD16. These eNK cells exerted significant cytotoxicity against cells from 34 B-CLL patients, with only 1 sample exhibiting resistance. This sporadic resistance did not correlate with match between KIR ligands expressed by the eNK cells and the leukemic cells, while cells with match resulted sensitive to eNK cells. This suggests that KIR mismatch is not relevant when expanded NK cells are used as effectors. In addition, we found two examples of de novo resistance to eNK cell cytotoxicity during the clinical course of the disease. Resistance correlated with KIR-ligand match in one of the patients, but not in the other, and was associated with a significant increase in PD-L1 expression in the cells from both patients. Treatment of one of these patients with idelalisib correlated with the loss of PD-L1 expression and with re-sensitization to eNK cytotoxicity. We confirmed the idelalisib-induced decrease in PD-L1 expression in the B-CLL cell line Mec1 and in cultured cells from B-CLL patients. As a main conclusion, our results reinforce the feasibility of using expanded and activated allogeneic NK cells in the treatment of B-CLL.

Understanding the spread of de novo and transmitted macrolide-resistance in Mycoplasma genitalium

Background The rapid spread of azithromycin resistance in sexually transmitted Mycoplasma genitalium infections is a growing concern. It is not yet clear to what degree macrolide resistance in M. genitalium results from the emergence of de novo mutations or the transmission of resistant strains. Methods We developed a compartmental transmission model to investigate the contribution of de novo macrolide resistance mutations to the spread of antimicrobial-resistant M. genitalium. We fitted the model to resistance data from France, Denmark and Sweden, estimated the time point of azithromycin introduction and the rates at which infected individuals receive treatment, and projected the future spread of resistance. Results The high probability of de novo resistance in M. genitalium accelerates the early spread of antimicrobial resistance. The relative contribution of de novo resistance subsequently decreases, and the spread of resistant infections in France, Denmark and Sweden is now mainly driven by transmitted resistance. If treatment with single-dose azithromycin continues at current rates, macrolide-resistant M. genitalium infections will reach 25% (95% confidence interval, CI [9–30]%) in France, 84% (95% CI [36–98]%) in Denmark and 62% (95% CI [48–76]%) in Sweden by 2025. Conclusions Blind treatment of urethritis with single-dose azithromycin continues to select for the spread of macrolide resistant M. genitalium. Clinical management strategies for M. genitalium should limit the unnecessary use of macrolides.

STEM-18. DISTINCT BUT PREDICTABLE MECHANISMS DRIVE GENETIC VS. EPIGENETIC RESISTANCE TO TARGETED THERAPY

Emergence of therapy resistance greatly reduces long-term utility of effective targeted therapies, including SMO/SHH pathway inhibitors. SHH signaling is activated in ~25% of human medulloblastomas (MB) and FDA approved SMOi (to treat basal cell carcinoma (BCC)) are currently in clinical trials for MBs and acute myeloid leukemia (AML). Accumulating clinical experience suggests that a significant number of BCC patients treated with SMOi develop acquired resistance over time and some show de novo resistance. A similar pattern is observed in MB patients, indicating the need to elucidate resistance mechanisms, particularly those driving de novo vs. acquired resistance, and develop new strategies to overcome both de novo and acquired resistance to SMOi. We report that we have discovered a novel, epigenetic mechanism of therapy resistance to SMOi that underlie de novo resistance. Using two different mouse models of SHH MB, we tested our original hypothesis that the selective pressure on cancer stem cells (CSCs), but not bulk tumor cells, will determine the resistance mechanism at the molecular level. We show that acquired mutations in the SHH pathway genes (previously reported mechanism of resistance) occur only in tumors that contain CSCs that depend on the SHH pathway. In tumors where only the bulk tumor cells, but not CSCs, depend on SHH signaling, no acquired mutations in the SHH pathway genes are detected. Instead, in these tumors, epigenetic reprogramming through selective degradation of specific histone modifiers results in global changes in the epigenetic cell state and gene expression patterns. Importantly, we can predict the mechanism of resistance in individual tumors prior to treatment based on CSC phenotypes. Finally, we also report biomarkers that can be used to identify tumors with CSCs that are independent of SHH pathway, which can be exploited to design anticipatory combination therapies in the future.

Genomic Profiling of KRAS/NRAS/BRAF/PIK3CA Wild-Type Metastatic Colorectal Cancer Patients Reveals Novel Mutations in Genes Potentially Associated with Resistance to Anti-EGFR Agents

Previous findings suggest that metastatic colorectal carcinoma (mCRC) patients with KRAS/NRAS/BRAF/PIK3CA wild-type (quadruple-wt) tumors are highly sensitive to anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (MoAbs). However, additional molecular alterations might be involved in the de novo resistance to these drugs. We performed a comprehensive molecular profiling of 21 quadruple-wt tumors from mCRC patients enrolled in the “Cetuximab After Progression in KRAS wild-type colorectal cancer patients” (CAPRI-GOIM) trial of first line FOLFIRI plus cetuximab. Tumor samples were analyzed with a targeted sequencing panel covering single nucleotide variants (SNVs), insertions/deletions (Indels), copy number variations (CNVs), and gene fusions in 143 cancer-related genes. The analysis revealed in all 21 patients the presence of at least one SNV/Indel and in 10/21 cases (48%) the presence of at least one CNV. Furthermore, 17/21 (81%) patients had co-existing SNVs/Indels in different genes. Quadruple-wt mCRC from patients with the shorter progression free survival (PFS) were enriched with peculiar genetic alterations in KRAS, FBXW7, MAP2K1, and NF1 genes as compared with patients with longer PFS. These data suggest that a wide genetic profiling of quadruple-wt mCRC patients might help to identify novel markers of de novo resistance to anti-EGFR MoAbs.