Autocrine and paracrine loops between cancer cells and macrophages promote lymph node metastasis via CCR4/CCL22 in head and neck squamous cell carcinoma.

Lymph node metastasis is a poor prognostic factor for patients with head and neck squamous cell carcinoma (HNSCC). However, its molecular mechanism has not yet been fully understood. In our study, we investigated the expression of CCR4 and its ligand CCL22 in the HNSCC tumor microenvironment and found that the CCR4/CCL22 axis was involved in lymph node metastasis of HNSCC. CCR4 was expressed in 20 of 31 (64.5%) human tongue cancer tissues, and its expression was significantly correlated with lymph node metastasis (p < 0.01) and lymphatic invasion (p < 0.05). CCR4 was expressed in three of five human HNSCC cell lines tested. CCR4(+) HNSCC cells, but not CCR4(-) cells, showed enhanced migration toward CCL22, indicating that functional CCR4 was expressed in HNSCC cell lines. CCL22 was also expressed in cancer cells (48.4% of tongue cancer tissues) or CD206(+) M2-like macrophages infiltrated in tumors and draining lymph nodes. CCL22 produced by cancer cells or CD206(high) M2-like macrophages increased the cell motility of CCR4(+) HNSCC cells in vitro in an autocrine or paracrine manner. In the mouse SCCVII in vivo model, CCR4(+) cancer cells, but not CCR4(-) cells, metastasized to lymph nodes which contained CCL22 producing M2-like macrophages. These results demonstrate that lymph node metastasis of CCR4(+) HNSCC is promoted by CCL22 in an autocrine or M2-like macrophage-dependent paracrine manner. Therefore, the CCR4/CCL22 axis may be an attractive target for the development of diagnostic and therapeutic strategies for patients with HNSCC.

Does a vascular supercharge improve the clinical outcome for free jejunal transfer?

To clarify whether a supercharged free jejunal transfer would have a different clinical outcome from the usual transfer method, we examined clinical data from cases of esophago-pharyngeal reconstruction. Fifty-three patients in whom the hypopharynx and cervical esophagus was reconstructed with a free jejunal transfer were divided into two groups: 19 normal procedures and 34 supercharged. Clinical outcomes including intraoperative and postoperative events, complications and deglutition were compared statistically. There were no significant differences between the groups in terms of the rates of free flap failure, leakage, stenosis, drinking status, dysphagia, or operating time. There were no significant advantages in clinical outcomes when using a supercharge. However, supercharged flaps with an intraoperative arterial thrombosis were all rescued and survived. Thus, a supercharge in free flap is not necessary for all cases. Its indication should be limited to cases when free flaps are not reliable because of intraoperative thrombosis and arterial insufficiency.

Successful retrograde arterial inflow through a muscular branch in a free anterolateral thigh chimeric flap transfer.

In this report, we present a case in which a free anterolateral thigh (ALT) flap was transferred for head and neck reconstruction after oropharyngeal cancer ablation, and a retrograde arterial inflow was used to salvage the flap when the main arterial pedicle showed usual repeated spasms. The flap was raised as a chimera flap comprising a fasciocutaneous flap and a vastus lateralis muscle flap. After reperfusion, the pedicle artery exhibited spasms repeatedly and vascular flow was unstable. Therefore, we performed arterial supercharge. In the distal portion of the muscle flap, a small arterial branch was dissected as a reverse-flow arterial pedicle. The recipient artery was also a retrograde limb of the superior thyroid artery. The flap survived; however, postoperative ultrasonographic echo evaluation revealed that the spastic descending branch of the lateral circumflex femoral artery was obstructed and that the reverse-flow muscular perforator alone nourished the whole flap. In free ALT flap transfer, a small perforator level artery was able to nourish a flap, even in a retrograde manner. Moreover, when the vasculature of the free flap is unstable, retrograde arterial supply to a small perforator can be an option to save the flap transfer.

Double arterialized free jejunal flap.

In a standard free jejunal transfer, one artery and one vein are anastomosed. However, when raising the jejunal flap, a one-segment jejunum sometimes has two arteries and one accompanying vein as a vascular pedicle. Free jejunal transfer in which two arteries and one vein are anastomosed was designed. We report on the safety and advantages of using this artery-dominant transfer when performing microvascular anastomosis. This technique was used when a one-segment jejunum had two arteries and an accompanying vein. Eight patients underwent this arterial-supercharged free jejunal transfer. All flaps survived, and no complications developed except for two cases of intraoperative thrombosis before the procedure. It is important to transfer the artery-rich graft into the same physiological environment by reconstructing the similar hemodynamics. The grafts can be transferred without harm. This artery-dominant method can be an option when conditions are unfavorable for safer jejunal transfer.

RB1CC1 activates the promoter and expression of RB1 in human cancer.

RB1-inducible coiled-coil 1 (RB1CC1, also known as FIP200) is a tumor suppressor implicated in the regulation of RB1 (retinoblastoma 1) expression. However, the molecular mechanism of RB1 regulation by RB1CC1 has not been elucidated. Here, we demonstrate that nuclear RB1CC1 binds to the RB1 promoter using chromatin immunoprecipitation assays with anti-RB1CC1 antibody. Luciferase assays with RB1 promoter reporter plasmids revealed that RB1CC1 activated the RB1 promoter through the 201 bp upstream GC-rich region (from the initiation ATG). Electrophoretic mobility shift assay and Western blot analysis supported RB1CC1 binding to the GC-rich region of the RB1 promoter. In addition, the C-terminus of RB1CC1 was required for nuclear localization and subsequent RB1 promoter activation. Furthermore, the expression levels of RB1CC1 and RB1 significantly correlated with in vivo breast cancer tissues as determined by immunohistochemical analysis. These data indicate that nuclear RB1CC1 directly activates the RB1 promoter to enhance RB1 expression in cancer cells. Evaluation of RB1CC1 in various types of human cancer tissues is expected to provide useful information for clinical practice and future therapeutic strategies.

Multiple myeloma involving the thyroid cartilage.

Multiple myeloma, solitary plasmacytoma, and extramedullary plasmacytoma constitute a continuous disease spectrum of plasma cell neoplasms. In the larynx, although extramedullary plasmacytoma in the supraglottic region has been sometimes reported, plasma cell neoplasm with involvement of the thyroid cartilage is extremely rare. We report a case of multiple myeloma involving the thyroid cartilage. A 72-year-old male patient presented with a pathological fracture of the cervical vertebrae. CT scan revealed low-density areas within the thyroid cartilage, but the laryngeal mucosa and submucosal soft tissue were intact. Multiple myeloma was diagnosed, since the tumors in the thyroid cartilage and cervical vertebrae revealed plasmacytoma. Because no other lesion was found, irradiation of the larynx and cervical vertebrae was performed. Neither aggressive change of these lesions nor new lesions have been found over 3-year follow-up following the initial treatment without adjuvant therapy.

p62/SQSTM1 levels predicts radiotherapy resistance in hypopharyngeal carcinomas.

Hypopharyngeal carcinoma is one of the worst prognostic malignancies among head and neck carcinomas. Therefore, a good biomarker should be identified to predict the best therapeutic option before starting the treatment. In cell models, p62/SQSTM1 levels affected the Nrf2-Keap1 pathway, ROS levels, GSH/GSSG ratios and cell growth, especially under irradiation rather than under CDDP exposure, which was toxic despite p62/SQSTM1 status. In a clinical cohort of hypopharyngeal carcinomas, high levels of p62/SQSTM1 significantly predicted poor prognosis (log-rank test, Chi-square value = 6.750, P = 0.0094) and maximum critical risk (Cox proportional hazard ratio = 4.405, P = 0.0086), especially in the radiotherapy group. Therefore, when p62/SQSTM1 is elevated in the biopsy section, hypopharyngeal carcinoma should be treated with surgical and/or chemotherapeutic options.

A case of severe dilatation of the parotid duct due to fibrinous sialodochitis.

A 50-year-old woman presented with a 10-year history of swelling of the left cheek during and after meals. She regularly pushed the cheek hard to decrease the swelling by excreting the saliva. She did not have pain or fever. She also complained of bronchial asthma and allergic rhinitis. Magnetic resonance imaging (MRI) revealed bead-like dilatation (3x4 cm) of the left parotid duct with hypointensity on T1-weighted MRI and hyperintensity on T2-weighted MRI. Technetium 99m-pertechnetate (Tc-99m) scintigraphy demonstrated hypofunction of the left parotid gland and retention of radioactive substrate in the left parotid duct even after acid loading. Since bougienage was impossible, we decided to perform a drainage operation. We exposed, fenestrated and sutured the duct wall to the buccal mucosa to make a large orifice. We inserted a Penrose drain for 1 month to avoid stenosis of the orifice. No complication was observed postoperatively, and drainage was still adequate at the most recent examination 3 years after the operation. Smears of saliva from the parotid duct with Hansel staining revealed numerous eosinophils, and fibrinous sialodochitis was diagnosed.

Aberrant Myosin 1b Expression Promotes Cell Migration and Lymph Node Metastasis of HNSCC.

UNLABELLED: Lymph node metastasis is the major clinicopathologic feature associated with poor prognosis in patients with head and neck squamous cell carcinoma (HNSCC). Here, web-based bioinformatics meta-analysis was performed to elucidate the molecular mechanism of lymph node metastasis of human HNSCC. Preferential upregulation of Myosin 1b (MYO1B) transcript in HNSCC datasets was identified. Myo1b mRNA was highly expressed in human HNSCC cells and patient tissue specimens compared with their normal counterparts as shown by quantitative PCR (qPCR) analyses. Immunohistochemistry (IHC)-detected Myo1b expression was significantly correlated with lymph node metastases in patients with oral cancer of the tongue. HNSCC with high expression of Myo1b and chemokine receptor 4 (CCR4), another metastasis-associated molecule, was strongly associated with lymph node metastasis. RNA interference (RNAi) of Myo1b in HNSCC cells, SAS and HSC4, significantly inhibited migratory and invasive abilities through decreased large protrusion formation of cell membranes. Finally, Myo1b knockdown in SAS cells significantly inhibited in vivo cervical lymph node metastases in a cervical lymph node metastatic mouse model system. IMPLICATIONS: Myo1b is functionally involved in lymph node metastasis of human HNSCC through enhanced cancer cell motility and is an attractive target for new diagnostic and therapeutic strategies for patients with HNSCC.

Enhanced production of matrix metalloproteinase-2 in human head and neck carcinomas is correlated with lymph node metastasis.

Matrix metalloproteinase (MMP)-2 and -9 degrade type IV collagen, which is one of the major components of the basement membrane in normal tissue and expressed in the surroundings of the cancer nest in squamous cell carcinoma. The degeneration of type IV collagen is an essential step in the metastasis to lymph nodes and distant organs. In this study, we examined MMP-2 and -9 levels of cancer tissue and serum obtained from patients with head and neck squamous cell carcinoma (HNSCC) in order to evaluate the relationship between the clinicopathologic features and MMPs. We examined the production of MMP-2 and -9 in cancer tissue homogenates of 73 patients who had HNSCC and the serum MMP levels of 16 patients with HNSCC and 8 healthy volunteers. We also studied the localization of MMP-2 in the carcinoma using an immunohistochemical approach. The concentrations of MMP-2 and -9 in the tissue homogenates and serum were measured by means of a sandwich enzyme immunoassay using a monoclonal antibody. Immunohistochemical analyses were performed with monoclonal antibody to MMP-2. The concentration of MMP-2 in the tumor tissue homogenates was unrelated to tumor size, but that in patients with lymph node metastases was significantly higher than in those without lymph node metastases. The concentration of MMP-9 was unrelated to lymph node metastasis and tumor size. The levels of both MMP-2 and -9 in serum were unrelated to lymph node metastasis. Immunohistochemistry indicated that MMP-2 was mainly expressed in cancer cells. Because MMP-2 degrades type IV collagen, the level of MMP-2 in carcinomas may be a useful indicator of the degree of invasion and metastasis.

Prognostic significance of RB1-inducible coiled-coil 1 in salivary gland cancers.

UNLABELLED: 7 BACKGROUND: No generally agreed-upon method is available for predicting the prognosis of salivary gland cancers. RB1-inducible coiled-coil 1 (RB1CC1) is a positive regulator for the retinoblastoma tumor suppressor (RB1) pathway, and is a suitable marker for evaluating the clinical course of breast cancer. We investigated whether RB1CC1 predicts the prognosis of salivary gland cancers. METHODS: Molecules involved in the RB1CC1 pathway, including RB1CC1, RB1, p53, and Ki-67, were evaluated immunohistochemically in 36 cases of salivary gland cancers. The relationships between clinicopathologic features and disease-free-survival intervals were analyzed by a Kaplan-Meier log-rank test and a multivariate Cox proportional hazard regression. RESULTS: Nuclear RB1CC1 loss in the tumors was significantly associated with a worse disease-free survival (log-rank test, chi-square value = 11.644, p = .0006), and was the maximum critical risk (multivariate Cox proportional hazard ratio = 11.112, 95% confidence interval [CI] = 1.776-69.510, p = .0100). CONCLUSIONS: Nuclear expression of RB1CC1 predicts a better clinical outcome and is useful in the follow-up of salivary gland cancers.

RB1CC1 activates the p16 promoter through the interaction with hSNF5.

RB1-inducible coiled-coil 1 (RB1CC1, also known as FIP200) is involved in dephosphorylation and increase of retinoblastoma tumor suppressor protein (RB1), but the RB1CC1 molecular mechanism in the dephosphorylation of RB1 is not fully understood. We determined that RB1CC1 activates the expression of p16 (also called INK4a/CDKN2a) through the activation of its promoter, using chromatin immunoprecipitation (ChIP) and p16 promoter-luciferase reporter assays. In addition, RB1CC1 essentially requires binding with hSNF5 (also known as BAF47/INI1, a chromatin-remodeling factor) to activate the p16 promoter, in order to enhance the RB1 pathway and acts as a tumor suppressor. Evaluation of the RB1CC1 mechanism of action is expected to provide useful information for clinical practice and future therapeutic strategies in human cancers.

Blood gas analyses in doubly-vascularised free jejunal transfers.

The vascular supercharge (additional microvascular anastomosis) has rarely been used for free flaps, and the blood circulation in the transferred tissue has not been recorded. We have made double vascular anastomoses during free jejunal transfer to reduce the possibility of loss of the flap from vascular occlusion. To evaluate the efficacy of additional arterial and venous anastomoses to improve the circulation in the transferred tissue, we analysed the results of blood gas measurements including venous partial pressure of oxygen (pO2) and carbon dioxide (pCO2) from the distal arcade vein. The free jejunal transfer was made using two pairs of arterial and venous anastomoses. Blood gas concentrations were analysed in samples drawn from the vein in the jejunal arcade before harvest, after the anastomosis of one paired artery and vein, after an additional arterial anastomosis, and after anastomoses of two pairs of artery/vein. The results showed that the venous pCO2 was not changed by increasing the number of anastomosed vessels. The venous pO2 was raised both by an additional arterial anastomosis and by two pairs of anastomoses, compared with that at the other two time points measured (p = 0.04, p = 0.02, respectively). An additional arterial anastomosis seemed to have more effect on the pO2 than an additional artery/vein pair. Additional arterial and venous supercharging therefore has a similar effect on hyperbaric oxygenation. This effect is mainly caused by arterial supercharging.

Interleukin-28B acts synergistically with cisplatin to suppress the growth of head and neck squamous cell carcinoma.

Interleukin-28B (IL-28B), also referred to as interferon-λ3, belongs to the type III interferon family. Earlier studies showed that IL-28B suppresses proliferation of some tumor cells in vitro. IL-28B gene transfection ex vivo also resulted in growth retardation of tumor cells in mice, through either direct antiproliferative action or induction of antitumor immunity. However, it has not been reported whether in vivo therapeutic administration of recombinant IL-28B can inhibit the growth of a pre-established tumor. Here, we found that repetitive subcutaneous administration of recombinant mouse IL-28B significantly induced tumor-specific cytotoxic T lymphocytes and augmented natural killer cytolytic activity, leading to moderate suppression of the growth of a murine head and neck squamous cell carcinoma (HNSCC) cell line that was completely resistant to the direct antiproliferative effect of IL-28B. Moreover, co-administration of recombinant mouse IL-28B and cisplatin (CDDP) more significantly inhibited in vivo growth of the tumor that had been established in syngenic mice and induced tumor-specific cytotoxic T lymphocytes. The CDDP treatment induced the expression of major histocompatibility complex class I and Fas molecules on the surface of HNSCC cells both in vitro and in vivo; this may be the mechanism underlying the synergistic tumor suppression activity of IL-28B and CDDP. Unlike type I interferon, IL-28B did not suppress growth of bone marrow cells in culture. Therefore, IL-28B may be useful as a tool for a novel multidisciplinary therapy against cancer, significantly potentiating innate and adaptive antitumor immune responses, especially when co-administrated with CDDP, which is currently the first choice chemotherapeutic agent against various tumors including HNSCCs.

RECQL1 and WRN proteins are potential therapeutic targets in head and neck squamous cell carcinoma.

RECQL1 and WRN proteins are RecQ DNA helicases that participate in suppression of DNA hyper-recombination and repair. In this study, we report evidence supporting their candidacy as cancer therapeutic targets. In hypopharyngeal carcinomas, which have the worst prognosis among head and neck squamous cell carcinomas (HNSCC) that are rapidly rising in incidence, we found that RECQL1 and WRN proteins are highly expressed and that siRNA-mediated silencing of either gene suppressed carcinoma cell growth in vitro. Similarly, siRNA administration in a murine xenograft model of hypopharyngeal carcinoma markedly inhibited tumor growth. Moreover, combining either siRNA with cis-platinum (II) diammine dichloride significantly augmented the in vivo anticancer effects of this drug that is used commonly in HNSCC treatment. Notably, we observed no recurrence of some tumors following siRNA treatment in this model. Our findings offer a preclinical proof of concept for RECQL1 and WRN proteins as novel therapeutic targets to treat aggressive HNSCC and perhaps other cancers.

Angioedema: 6 years experience with fourteen cases.

OBJECTIVE: To study the difference in the findings between the causes of angioedema and the characteristics of angioedema induced by angiotensin receptor II blockers (ARBs), and to investigate whether laboratory examinations for acute phase inflammatory markers can aid in diagnosis and predict airway risk. METHODS: We retrospectively reviewed fourteen cases of patients with angioedema that were treated from 2000 to 2006. Data were collected regarding age, sex, location of the edema, cause, time course of resolution and laboratory examinations (leukocyte counts, serum C-reactive protein (CRP) level, complement function and the activity of C1 esterase inhibitor). RESULTS: The causes of angioedema were ACEIs in six patients (42.9%), candesartan (ARB) in three (21.4%), HAE (types 1 and 2) in two, and unknown in three. Of these patients, 71.4% exhibited edema in the floor of the mouth, irrespective of the cause. Two patients with edema induced by candesartan exhibited both lingual and laryngeal edemas. The remaining one with candesartan-induced edema exhibited edema in the neck and mediastinum and pleural effusion. The average time to resolution was 4.1 days, ranging from one to twelve days. The edema in eleven patients resolved with conservative therapy, while three patients underwent tracheotomy. In two patients with candesartan-induced edema, although the edemas resolved completely after cessation of candesartan administration, the edemas reappeared in the same locations, two and thirty days after the cessation of candesartan for each patient. None of the patients with angioedema induced by ACEIs exhibited elevation of serum CRP levels. No significant differences were found for leukocyte counts and serum CRP levels between patients with angioedemas induced by ACEIs, ARB and those of unknown cause. No significant differences were observed in the above findings between the patients who underwent tracheotomy and those who did not. Two patients exhibited low C4 levels, and one of the two exhibited no activity of C1 esterase inhibitor. CONCLUSION: Consistent with previous reports, angioedema in the floor of the mouth extending to the tongue should be considered as a possible risk factor for airway compromise. Laboratory examinations for acute phase inflammatory markers are not useful for diagnosis and are not predictive for airway intubation and tracheotomy. Angioedema induced by candesartan can present in anomalous sites and reappear following drug cessation even if the edema has resolved completely.

Double vascular anastomosis in the neck for reliable free jejunal transfer.

To reduce the possibility of necrosis in free jejunal transfer after total pharyngolaryngo-oesophagectomy, we made a second set of arterial and venous anastomoses in addition to the usual cervical arterial and venous anastomoses. To obtain two different arterial flows (carotid and subclavian systems), the recipient arteries were the superior thyroid and the transverse cervical. For venous flow, the internal and external jugular veins were used. All flaps survived. This procedure, which is limited to the already dissected neck with no procedures in other areas, is less invasive than others. Its advantages are that when one vessel has thrombosed the other vessel functions as a safety valve, and the greater pliability of the vascular pedicles makes it easier to reach the recipient vessels. Because this method is theoretically safe and results in less possibility of losing a flap when the anastomosis is unreliable, the double-pedicled transfer can be an option for safer free jejunal transfer.

Expression of CC-chemokine receptor 7 (CCR7) and CXC-chemokine receptor 4 (CXCR4) in head and neck squamous cell carcinoma.

OBJECTIVES: We tried to clarify the correlation of the expression of CCR7 and CXCR4 with lymph node and distant metastasis. MATERIALS AND METHODS: We examined expression of CCR7 and CXCR4 in 9 HNSCC cell lines and 25 HNSCC tissues by semi-quantitative RT-PCR and immunohistochemistry study. We examined the expression levels of CCR7 and CXCR4 in undifferentiated and differentiated human normal keratinocyte. RESULTS: All cell lines expressed CCR7 mRNA, and three expressed CXCR4 mRNA. CCR7 and CXCR4 mRNAs were significantly higher in HNSCC tissues than in non-neoplastic tissues (p<0.05, respectively) and correlated with lymph node metastasis (p<0.05, respectively). The level of CXCR4 mRNA also correlated with distant metastasis (p<0.05). Immunohistochemistry demonstrated localization of CCR7 and CXCR4 to carcinoma cells and lymphocytes and immunohistochemical staining scores of CCR7 and CXCR4 also showed similar correlation to lymph node and distant metastasis with CCR7 and CXCR4 mRNA levels. The level of CCR7 mRNA was significantly higher in poorly and moderately differentiated than in well-differentiated HNSCC (p<0.05). The level of CCR7 mRNA in undifferentiated keratinocyte was significantly higher than that in differentiated keratinocyte. CONCLUSION: The expression of CCR7 in HNSCC increases by dedifferentiation and plays an important role in lymph node metastasis of HNSCC and CXCR4 plays an important role in lymph node metastasis as well as distant metastasis.

RB1CC1 together with RB1 and p53 predicts long-term survival in Japanese breast cancer patients.

RB1-inducible coiled-coil 1 (RB1CC1) plays a significant role in the enhancement of the retinoblastoma tumor suppressor (RB1) pathway and is involved in breast cancer development. However, RB1CC1's role in clinical progression of breast cancer has not yet been evaluated, so, as a first step, it is necessary to establish its usefulness as a tool to evaluate breast cancer patients. In this report, we have analyzed the correlation between abnormalities in the RB1CC1 pathway and long-term prognosis, because disease-specific death in later periods (>5 years) of the disease is a serious problem in breast cancer. Breast cancer tissues from a large cohort in Japan were evaluated by conventional immunohistochemical methods for the presence of the molecules involved in the RB1CC1 pathway, including RB1CC1, RB1, p53, and other well-known prognostic markers for breast cancer, such as estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. The correlation between the immunohistochemical results and clinical outcomes of 323 breast cancer patients was analyzed using a Kaplan-Meier log-rank test and a multivariate Cox proportional hazards regression analysis. Absence of nuclear RB1CC1 expression was associated with the worst prognosis (Log-rank test, Chi-Square value = 17.462, p<0.0001). Dysfunction of either one of RB1CC1, RB1, or p53 was associated with the highest risk for cancer-specific death, especially related to survival lasting more than 5 years (multivariate Cox proportional hazard ratio = 3.951, 95% Confidence Interval =1.566-9.967, p = 0.0036). Our present data demonstrate that the combined evaluation of RB1CC1, RB1 and p53 by conventional immunohistochemical analysis provides an accurate prediction of the long-term prognoses of breast cancer patients, which can be carried out as a routine clinical examination.

RB1CC1 activates RB1 pathway and inhibits proliferation and cologenic survival in human cancer.

RB1-inducible coiled-coil 1 (RB1CC1, also known as FIP200) plays a role in the enhancement of the RB1 pathway through the direct binding to a GC-rich region 201bp upstream (from the initiation ATG) of the RB1 promoter. Here, we identified hSNF5 and p53 as the binding partners of RB1CC1 by immunoprecipitation and immunofluorescence assays. Interaction between these molecules and the RB1 pathway was analyzed by the assays of chromatin immunoprecipitation, luciferase-reporter, reverse transcription-polymerase chain reaction and immunoblot. The tumor growth suppression by RB1CC1 was evaluated by flow cytometry or by a cell growth assay. The nuclear RB1CC1 complex involving hSNF5 and/or p53 activated transcription of RB1, p16 and p21, and suppressed tumor cell growth. Furthermore, nuclear RB1CC1 expression significantly correlated with those of RB1 and p16 in breast cancer tissue in vivo, and the Ki-67 proliferation index was dependent on p53 as well as RB1CC1. The present study indicates that RB1CC1 together with hSNF5 and/or p53 enhances the RB1 pathway through transcriptional activation of RB1, p16 and p21. Evaluation of RB1CC1 expression combined with RB1 and p53 status is expected to provide useful information in clinical practice and future therapeutic strategies in breast cancer.