Protein Kinase D3 as a Novel Biomarker for Triple-negative Breast Cancer

描述（由申请人提供）：三阴性乳腺癌（TNBC），特征为缺乏雌激素受体（ER）、孕激素受体（PR）和HER 2的乳腺肿瘤，占所有乳腺癌的15-20%。TNBC主要包括乳腺癌的基底样分子亚型，并且具有独特的临床和病理特征。TNBC代表了一个重要的临床挑战，因为它的侵略性行为和总生存率差; TNBC患者复发和死亡的风险很高。目前，缺乏TNBC的靶向治疗，使化疗成为治疗的主要手段。因此，需要鉴定TNBC的新风险生物标志物以预防疾病复发并改善TNBC患者的治疗和护理。在这个提议中，我们试图确定丝氨酸/苏氨酸蛋白激酶D3（PKD 3）是否是TNBC的新生物标志物。PKD家族激酶包括PKD 1、PKD 2和PKD 3。我们最近发现PKD 2和PKD 3是乳腺癌细胞中表达的两种主要PKD亚型。与PKD 2不同，PKD 3在乳腺癌细胞系中的表达各不相同。我们发现PKD 3在致瘤性TNBC细胞系（HCC 1806和MDA-MB 468）和稳定表达表皮生长因子受体（EGFR）的T47 D乳腺癌细胞中高度表达。相反，ER阳性和HER 2过表达乳腺癌细胞系中PKD 3蛋白水平较低。通过使用PKD亚型特异性siRNA，我们已经鉴定PKD 3为在致瘤性HCC 1806 TNBC细胞中介导PKD信号转导和细胞增殖的重要亚型。我们进一步表明，表达高水平PKD 3的乳腺癌细胞比表达低水平PKD 3的HER 2过表达乳腺癌细胞对PKD抑制剂更敏感。基于这些发现，我们假设PKD 3可能是乳腺癌，特别是侵袭性TNBC的重要生长调节因子和风险生物标志物。我们将通过以下两个具体目的来检验这一假设：目的1）确定PKD 3在乳腺肿瘤中的表达，并将其表达与乳腺癌亚型和肿瘤恶性程度相关联;目的2）确定PKD 3在体内TNBC生长和信号传导中的作用。我们预计，这一提议将提供有价值的直接证据，以评估与其他乳腺癌亚型相比，侵袭性TNBC是否表达更多的PKD 3，以及PKD 3是否是TNBC体内关键的生长调节因子。这些研究可能会发现PKD 3可能是TNBC的一种新的风险生物标志物。

DESCRIPTION (provided by applicant): Triple-negative breast cancer (TNBC), characterized by breast tumors lacking estrogen receptor (ER), progesterone receptor (PR) and HER2, comprises 15-20% of all breast cancers. TNBC mostly comprises the basal-like molecular subtype of breast cancer and has distinct clinical and pathologic features. TNBC represents an important clinical challenge because of its aggressive behavior and poor overall survival; and patients with TNBC have a high risk of relapse and death. Currently, targeted therapies for TNBC are lacking, leaving chemotherapy as the mainstay of treatment. Hence identification of new risk biomarkers for TNBC is needed to prevent the disease relapse and to improve treatment and care for patients with TNBC. In this proposal, we seek to determine whether the serine/threonine protein kinase D3 (PKD3) is a novel biomarker for TNBC. PKD family kinases include PKD1, PKD2 and PKD3. We have recently shown that PKD2 and PKD3 are two major PKD isoforms expressed in breast cancer cells. Unlike PKD2, PKD3 expression varied among breast cancer cell lines. We found that PKD3 was highly expressed in tumorigenic TNBC cell lines (HCC1806 and MDA-MB468) and in T47D breast cancer cells stably expressing epidermal growth factor receptor (EGFR). In contrast, PKD3 protein level was low in ER-positive and HER2-overexpressing breast cancer cell lines. By using PKD isoform-specific siRNAs, we have identified PKD3 as an important isoform mediating PKD signal transduction and cell proliferation in tumorigenic HCC1806 TNBC cells. We further showed that breast cancer cells expressing a high level of PKD3 were more responsible to PKD inhibitors compared with HER2- overexpressing breast cancer cells that have a low PKD3 level. On the basis of these findings, we hypothesize that PKD3 may be an important growth regulator and risk biomarker for breast cancer, especially for aggressive TNBC. We will test this hypothesis with following two Specific Aims: Aim 1) To determine the expression of PKD3 in breast tumors and correlate its expression with breast cancer subtypes and tumor malignancy; Aim 2) To determine the role of PKD3 in the growth and signaling of TNBC in vivo. We anticipate that this proposal will provide valuable direct evidence to assess whether the aggressive TNBC expresses more PKD3 compared with other breast cancer subtypes and whether PKD3 is a critical growth regulator of TNBC in vivo. These studies may lead to a finding that PKD3 could be a novel risk biomarker for TNBC.