Monomerization of Homodimeric Trefoil Factor 3 (TFF3) by an Aminonitrile Compound Inhibits TFF3-Dependent Cancer Cell Survival

Trefoil factor 3 (TFF3) is a secreted protein with an established oncogenic function and a highly significant association with clinical progression of various human malignancies. Herein, a novel small molecule that specifically targets TFF3 homodimeric functions was identified. Utilizing the concept of reversible covalent interaction, 2-amino-4-(4-(6-fluoro-5-methylpyridin-3-yl)phenyl)-5-oxo-4H,5H-pyrano[3,2-c]chromene-3-carbonitrile (AMPC) was identified as a molecule that interacted with TFF3. AMPC monomerized the cellular and secreted TFF3 homodimer at the cysteine (Cys)57-Cys57 residue with subsequent more rapid degradation of the generated TFF3 monomers. Hence, AMPC treatment also resulted in cellular depletion of TFF3 with consequent decreased cell viability in various human carcinoma-derived TFF3 expressing cell lines, including estrogen receptor positive (ER+) mammary carcinoma (MC). AMPC treatment of TFF3 expressing ER+ MC cells significantly suppressed total cell number in a dose-dependent manner. Consistently, exposure of TFF3 expressing ER+ MC cells to AMPC decreased soft agar colony formation, foci formation, and growth in suspension culture and inhibited growth of preformed colonies in 3D Matrigel. AMPC increased apoptosis in TFF3 expressing ER+ MC cells associated with decreased activity of EGFR, p38, STAT3, AKT, and ERK, decreased protein levels of CCND1, CCNE1, BCL2, and BCL-XL, and increased protein levels of TP53, CDKN1A, CASP7, and CASP9. siRNA-mediated depletion of TFF3 expression in ER+ MC cells efficiently abrogated AMPC-stimulated loss of cell viability and CASPASE 3/7 activities. Furthermore, in mice bearing ER+ MC cell-generated xenografts, AMPC treatment significantly impeded xenograft growth. Hence, AMPC exemplifies a novel mechanism by which small molecule drugs may inhibit a dimeric oncogenic protein and provides a strategy to impede TFF3-dependent cancer progression.

Abstract P2-06-12: Oncogenic potential of Trefoil factor 3 in initiation of mammary carcinoma through suppression of p53 pathway

Background

Oncogenic transformation is a complex multistep process where normal cells acquire the hallmarks of cancer, leading to unrestrained outgrowth of malignant clones. Trefoil Factor 3 (TFF3) is a clinically validated and functionally potent oncogene in mammary carcinoma. Elevated TFF3 expression has been consistently observed in mammary carcinoma, being involved in cancer progression. The present study investigates the potential functional role and the underlying mechanisms of TFF3 in promoting oncogenic transformation early in the onset of mammary carcinoma.

Material and method

Immortalized human mammary epithelial cells (HMECs): HMEC-hTERT, MCF10A and MCF12A, with forced expression of TFF3, were used as in vitro models and in an orthotopic xenograft model to study the oncogenic roles of TFF3. Furthermore, microarray analysis, immunofluorescence, and ubiquitination and CHX chase assays were used to examine the involvement of p53 pathway in TFF3 mediated-oncogenic transformation.

Results

Immortalized HMECs with forced expression of TFF3 exhibited the capacity of anchorage independent growth in the soft agar colony formation assay, which is a hallmark of oncogenic transformation. The forced expression of TFF3 also enhanced 3D growth of the immortalized HMECs in matrigel. Furthermore, immortalized HMECs with forced expression of TFF3 gaverise to orthotopic xenograft tumors in nude mice, which are not observed in mice injected with immortalized HMECs. These observations suggest that TFF3 stimulates the oncogenic transformation of non-malignant immortalized HMECs. In addition, the forced expression of TFF3 promoted aberrant cell proliferation, resistance to apoptosis, and increased cell migration and invasion of the HMECs, all these being important hallmarks of cancer. Here, we showed that TFF3-mediated oncogenic transformation of the immortalized HMEC-hTERT cells is dependent on p53 signaling pathway suppression. Mechanistically, TFF3 downregulated NF-κB (p65)-mediated transcription of p53 through decreasing NF-κB (p65) expression and nuclear accumulation. TFF3 also decreased p53 protein levels through post-transcriptional regulation. The forced expression of TFF3 increased MDM2 expression, resulting in an increased ubiquitin-mediated proteasomal degradation of p53. Moreover, forced expression of TFF3 decreased the cleaved form of MDM2, which is responsible for stabilizing p53 protein. Concordantly, HMECs with forced expression of TFF3 exhibited shorter p53 protein half-life as compared to vector control HMECs .

Conclusion

In summary, our study highlights the oncogenic potential of TFF3 in the initiation of mammary carcinoma through the suppression of the p53 pathway.

Citation Format: Chen RM, Pandey V, Chong QY, Poh HM, Zhang MY, Kumar AP, Lobie PE. Oncogenic potential of Trefoil factor 3 in initiation of mammary carcinoma through suppression of p53 pathway [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-06-12.

Abstract P6-20-09: Pharmacological inhibition of TFF3 enhances chemo-sensitivity and overcomes acquired resistance in breast cancer

Background

Dose-dependent toxicity and acquired chemo-resistance are two major challenges in the use of doxorubicin in breast cancer treatment. Trefoil factor 3 (TFF3) is a secreted ligand that promotes breast cancer progression and predicts poor survival outcome of breast cancer patients. It has also been shown to confer resistance to anti-estrogens and trastuzumab in breast cancer. Here, the role of TFF3 in regulating the sensitivity and acquired resistance to doxorubicin in breast cancer was investigated.

Methods

MCF7, ZR-75-1 and BT474 breast cancer cell lines with siRNA-mediated depletion of TFF3, and doxorubicin-resistant MCF7 cells generated from the pulsatile exposure to doxorubicin, were used as in vitromodels. We have developed a novel non-toxic small molecule inhibitor of TFF3 (AMPC) that binds specifically to cysteine 57 residue of dimeric TFF3 and promotes its dissociation to monomers thereby, inhibiting its dimeric functions such as proliferation and apoptosis. Here, the effects of AMPC in enhancing doxorubicin sensitivity and overcoming acquired doxorubicin resistance in breast cancer cells were also explored.

Results

Consistent with siRNA-mediated depletion of TFF3, pharmacological inhibition of TFF3 by AMPC enhanced doxorubicin-mediated decrease in cell viability, foci formation and 3D growth of the breast cancer cells, suggesting that TFF3 inhibition increased the sensitivity of these cells to doxorubicin treatment. Notably, AMPC combined with doxorubicin in a synergistic manner, enabling doxorubicin dose reduction for the same inhibitory effect. Doxorubicin-induced AKT activation has been reported to antagonize the effects of doxorubicin and promote its resistance in breast cancer. Here, the inhibition of TFF3 by AMPC was shown to reduce AKT activation. Mechanistically, AMPC co-treatment suppressed doxorubicin-induced AKT activation thereby enhancing doxorubicin-induced apoptosis, with an overall up-regulation of pro-apoptotic and down-regulation of anti-apoptotic proteins, as compared to doxorubicin monotherapy. TFF3 also mediated the acquired doxorubicin resistance in MCF7 cells. Elevated expression of TFF3 was observed in the doxorubicin-resistant MCF7 cells as compared to the parental MCF7 cells, while the inhibition of TFF3 by AMPC completely abrogated the resistant phenotype of these cells as shown in the cell viability, foci formation and 3D growth assays. In concordance with the elevated levels of TFF3, doxorubicin-resistant MCF7 cells also exhibited increased activation of AKT with reduced susceptibility to doxorubicin-induced apoptosis as compared to the parental MCF7 cells. Consistently, this was reversed with AMPC co-treatment, which suppressed the elevated levels of activated AKT in the doxorubicin-resistant MCF7 cells, resulting in the re-sensitization of these resistant cells to doxorubicin-induced apoptosis. Similar to that in the parental cells, AMPC also exhibited a synergistic inhibitory effect with doxorubicin in the doxorubicin-resistant MCF7 cells.

Conclusion

The pharmacological inhibition of TFF3 with AMPC is a potential therapeutic approach to reduce the dose-dependent toxicity and to overcome the acquired resistance of doxorubicin in breast cancer.

Citation Format: Poh HM, Chong QY, Chen RM, Pandey V, Salundi B, Kumar AP, Lee SC, Lobie PE. Pharmacological inhibition of TFF3 enhances chemo-sensitivity and overcomes acquired resistance in breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-20-09.

DUSP10 regulates intestinal epithelial cell growth and colorectal tumorigenesis

Dual specificity phosphatase 10 (DUSP10), also known as MAP kinase phosphatase 5 (MKP5), negatively regulates the activation of MAP kinases. Genetic polymorphisms and aberrant expression of this gene are associated with colorectal cancer (CRC) in humans. However, the role of DUSP10 in intestinal epithelial tumorigenesis is not clear. Here, we showed that DUSP10 knockout (KO) mice had increased intestinal epithelial cell (IEC) proliferation and migration and developed less severe colitis than wild-type (WT) mice in response to dextran sodium sulphate (DSS) treatment, which is associated with increased ERK1/2 activation and Krüppel-like factor 5 (KLF5) expression in IEC. In line with increased IEC proliferation, DUSP10 KO mice developed more colon tumours with increased severity compared with WT mice in response to administration of DSS and azoxymethane (AOM). Furthermore, survival analysis of CRC patients demonstrated that high DUSP10 expression in tumours was associated with significant improvement in survival probability. Overexpression of DUSP10 in Caco-2 and RCM-1 cells inhibited cell proliferation. Our study showed that DUSP10 negatively regulates IEC growth and acts as a suppressor for CRC. Therefore, it could be targeted for the development of therapies for colitis and CRC.