Goro Yokoyama

Cell growth inhibition by all‐trans retinoic acid in SKBR‐3 breast cancer cells: Involvement of protein kinase Cα and extracellular signal‐regulated kinase mitogen‐activated protein kinase

All‐trans retinoic acid (ATRA), a synthetic derivative of vitamin A, inhibits the growth of breast cancer cells. To elucidate the mechanism by which ATRA causes cell growth inhibition, we examined changes in cell cycle and intracellular signaling pathways, focusing on protein kinase C (PKC) and mitogen‐activated protein kinase (MAPK). Using the estrogen receptor‐negative, retinoid receptor–positive breast cancer cell line SKRB‐3, we found that treatment with ATRA significantly decreased the expression of PKCα, as well as reducing ERK MAPK phosphorylation. ATRA treatment leads to dephosphorylation of Rb, and consequently to G1 arrest. Marked changes in the expression of cyclins (particularly cyclins A and E) were observed in SKBR‐3 cells treated with ATRA. Using a series of pharmacological and molecular approaches, we found evidence that ATRA‐induced SKBR‐3 cell growth inhibition involves the deregulation of the PKCα‐MAPK pathway. These data suggest that retinoids interfered with signal transduction pathways that are crucial for cell cycle progression, and highlight the complexities of the biological effects of retinoid derivatives.

Preclinical and Clinical Studies of Novel Breast Cancer Drugs Targeting Molecules Involved in Protein Kinase C Signaling, the Putative Metastasis-Suppressor Gene Cap43 and the Y-box Binding Protein-1

Breast cancer is a common cause of tumors in women. The development of effective adjuvant therapies using drugs such as anthracyclines, taxanes, and aromatase inhibitors has improved the survival of breast cancer patients. Molecular cancer therapeutics are also attracting attention, and targeted molecular therapies, such as trastuzumab, have already contributed to effective new treatments for breast cancer. Other candidate targeted molecular therapies for breast cancer, including erlotinib, gefitinib, lapatinib, bevacizumab, and celecoxib, are currently undergoing clinical evaluation, and promising results are expected. The current review provides an up-to-date summary of the preclinical and clinical development of these drugs for breast cancer. In particular, we focus on therapies targeting protein kinase C (PKC) signaling, the putative metastasis-suppressor gene Cap43/N-myc downstream-regulated gene 1 (NDRG1)/differentiation-related gene-1 (Drg-1), and the Y-box binding protein-1 (YB-1). The PKC signaling pathway is widely considered to be a promising target for the development of novel therapeutics. Cap43 expression is significantly modulated by estrogen and/or anti-estrogens in breast cancer cells that are positive for estrogen receptor-alpha (ER-alpha). Cap43 is therefore of particular interest as a molecular indicator of the therapeutic efficacy of anti-estrogenic agents in breast cancer. The nuclear expression of YB-1 plays an essential role in the acquisition of malignant characteristics by breast cancer cells, through epidermal growth factor receptor 2 (HER2)-Akt-dependent pathways. Basic research investigating the key selective molecular changes that sustain breast cancer growth and progression, as demonstrated for PKC, Cap43, and YB-1, is allowing the development of specific targeted molecular diagnostics and therapeutics.

Axillary Lymph Node Recurrence of Papillary Thyroid Microcarcinoma: Report of a Case

We report a case of axillary lymph node recurrence of thyroid papillary microcarcinoma (PMC) in a 51-year-old woman who had undergone thyroidectomy with lymph node dissection 5 years earlier. We performed residual thyroid resection with cervical and bilateral axillary lymph node dissection, and pathological examination revealed well-differentiated papillary carcinoma, with partial poor differentiation. Postoperative radioiodine therapy was ineffective, and the patient died of systemic dissemination of the recurrence 8 months after her second operation. The positive cell rates of proliferating cell nuclear antigen and Ki-67 were clearly higher in the recurrent lymph nodes than in the primary thyroid tumor, suggesting increased cell proliferation in the recurrent lymph nodes. Thyroid papillary carcinoma rarely recurs in the axillary lymph nodes, but its possibility must be kept in mind, especially in patients with remarkable cervical lymph node metastasis and those who undergo extensive lymph node dissection.

Preclinical studies of molecular-targeting diagnostic and therapeutic strategies against breast cancer

We have investigated protein kinase C (PKC) signaling, a putative differentiation-related and metastasis suppressor gene Cap43/NDRG1/Drg-1, and Y-box binding protein-1 (YB-1) to identify new molecular targeting for breast cancer. PKC is a family of serine/threonine kinases that is involved in the regulation of cell growth. We have demonstrated that PKC caused G1 arrest in a breast cancer cell line through a mechanism involving a PKC–ERK MAPK–JNK–Rb protein signaling pathway. We have also characterized a novel mechanism through which all-trans retinoic acid (ATRA) and antineoplaston, anticancer drug, caused cell growth inhibition in breast cancer cells through effects on intracellular pathways. ATRA decreased the expression of PKCα, as well as reduced ERK MAPK phosphorylation, and consequently caused G1 arrest. Antineoplaston caused the down-regulation of PKCα protein expression, resulting in inhibition of ERK MAPK phosphorylation, with resultant inhibition of Rb phosphorylation leading to G1 arrest. PKC signaling represents a promising target for development of novel therapeutic agents. Cap43 is known as N-myc downstream-regulated gene 1 (NDRG1). Treatment with estradiol (E2) significantly decreased the expression of Cap43 in ER-α-positive breast cancer cell lines. Co-administration of tamoxifen abrogated the E2-induced downregulation of Cap43 in ER-α-positive cell lines. These results suggested that Cap43 may hold the potential of being a molecular marker to determine the therapeutic efficacy of anti-estrogenic anticancer agents in breast cancer. YB-1 is a member of the cold shock domain protein family. The expression of nuclear YB-1 was correlated with HER2 positively in clinical specimens of human breast cancer. Immunostaining studies showed that nuclear YB-1 expression was an independent prognostic factor of overall survival. Expression of nuclear YB-1 played an essential role in acquirement of malignant characteristics through HER2-dependent pathways in breast cancer patients. PKC, Cap43 and YB-1 may be useful in new molecular-targeting diagnosis and therapeutics in breast cancer.

Advanced chemoresistant breast cancer responding to multidisciplinary treatment with hyperthermia, radiotherapy, and intraarterial infusion.

We employed multidisciplinary therapy, consisting of hyperthermia, radiotherapy, and intraarterial infusion, for a patient with progressive advanced breast cancer that was resistant to epirubicin hydrochloride and cyclophosphamide (EC) therapy as well as being resistant to docetaxel hydrate, and obtained a good therapeutic response. Because estrogen and progesterone receptors were both negative and HER2 was 3(+), administration of trastuzumab was started, and this patient has shown no signs of recurrence at 33 months after our treatment. The results suggested that our multidisciplinary therapy can be an effective method for the treatment of progressive breast cancer showing resistance to major chemotherapy agents such as anthracyclines and taxanes.

Adenomyoepithelioma of the breast diagnosed by a mammotome biopsy: Report of a case

Adenomyoepithelioma is an uncommon primary breast tumor. It is conspicuous for two elements of the tumor, namely, ductal and myoepithelial components. Recently, a Mammotome biopsy, or stereotactic vacuum-assisted biopsy has become popular and various benign or borderline lesions are obtained. We report an adenomyoepithelioma of the breast in a 56-year-old woman. She was pointed out to have a cluster of some microcalcifications on mammography and a 9-mm hypoechoic mass lesion was detected by ultrasound. A Mammotome biopsy revealed a well-defined lesion. Histologically, the tumor demonstrated a thick and bi-cellular growth pattern consisting of ducts and myoepithelium. Immunohistochemically, epithelial cells were positive for cytokeratin AE1/AE3 and cytokeratin, epithelial membrane antigen (EMA), and carcinoembryonic antigen (CEA), negative for alpha-smooth muscle actin (alpha-SMA). In addition, myoepithelial cells were positive for alpha-SMA and CEA, which were scatterly positive for cytokeratin AE1/AE3, and negative for EMA. In examinations of non-palpable lesions found on mammography and ultrasound, a Mammotome biopsy is useful for making diagnosis, however, and adenomyoepithelioma is rarely found. In diagnosing such a rare disease from the limited information obtained from a needle biopsy, an immunohistochemical study was thus found to be useful for making a differential diagnosis.