3-amino thioacridone inhibits DNA synthesis and induce DNA damage in T-cell acute lymphoblastic leukemia (T-ALL) in a p16-dependent manner.

In T-cell Acute Lymphocytic Leukemia (T-ALL), the inhibitors of cyclin-dependent kinases (CDK) 4 and 6, p16 and p15, are inactivated almost universally at the DNA, RNA and protein levels. This suggests that CDK-targeting may be an effective therapeutic approach for T-ALL and other cancers. In this study, we tested 3 inhibitors of CDK4, 3-aminothioacridone (3-ATA), thioacridone (TA), and oxindole, for their effects on DNA synthesis and viability in primary T-ALL. Each compound was an effective inhibitor, with overall IC(50)s in similar ranges. In colony formation assay, leukemic cells were approximately 10-fold more sensitive to 3-ATA than normal bone marrow cells. When sorted by G1 protein status of T-ALL, p16(+), p15(+) or pRb(-) samples were significantly less sensitive to 3-ATA and TA, but not to oxindole, than p16(-), p15(-) or pRb(+) samples. There was no relationship of sensitivity with ARF expression. Despite their in vitro function as inhibitors of CDK4, 3-ATA did not inhibit pRb phosphorylation or cause G1 arrest, but did cause DNA damage and result in the induction and phosphorylation of p53. We conclude that 3-ATA efficacy can be predicted by p16 status in T-ALL, but the mechanism of action may be distinct from their in vitro ability to regulate CDK4 kinase activity

Prediction of axillary lymph node status of breast cancer patients by tumorbiological factors of the primary tumor.

BACKGROUND AND PURPOSE: The increasing use of systemic adjuvant therapy even in lymph node-negative breast cancer patients and breast cancer screening programs detecting smaller tumors with less probability of metastatic lymph nodes questions the need for routine axillary lymph node dissection. Since morbidity of breast cancer surgery is predominantly related to axillary lymph node dissection, predictive models for lymph node involvement may provide a way to avoid lymph node surgery and its side effects in subgroups of patients. PATIENTS AND METHODS: Using a multivariate logistic regression model, tumorbiological parameters such as expression of estrogen and progesterone receptors, Ki-67, p53, cathepsin D, HER2, S-phase fraction, and ploidy were analyzed regarding their ability to predict axillary lymph node involvement in 655 breast cancer patients. RESULTS: The model correctly predicted axillary lymph node metastases in 58% of the patients by including expression of progesterone receptor, HER2, and Ki-67. In a subgroup of 200 patients predicted to be at extremely high or extremely low risk for axillary lymph node metastases, the accuracy of the prediction was 70%. CONCLUSION: With a model just based on tumorbiological parameters obtained in the primary tumor it is possible to predict axillary lymph node status. By including additional parameters it appears to be feasible to further improve the model in order to avoid axillary lymph node surgery in low-risk women.

Expression profiles and clinical relationships of ID2, CDKN1B, and CDKN2A in primary neuroblastoma.

Despite considerable research into the etiology of neuroblastoma, the molecular basis of this disease has remained elusive. In contrast to the absence of expression of the known tumor suppressor CDKN2A (also known as p16 and INK4A) in a wide variety of tumor types we have found in previous studies that CDKN2A protein is paradoxically highly expressed in many advanced stage neuroblastomas and unrelated to RB1 status. In the present study, we sought to identify the mechanistic relationships that might influence CDKN2A expression and negate its influence on tumor cell proliferation. In this regard, we examined the role of the tumor-suppressor gene CDKN1B (also known as p27 and Kip1) and the oncogene ID2 in relationship to CDKN2A expression, MYCN amplification, and neuroblastoma pathogenesis in 17 neuroblastoma cell lines and 129 samples of primary tumors of all stages. All neuroblastoma cell lines expressed the ID2 transcript and protein. However, although the majority of primary neuroblastomas also expressed the ID2 transcript, expression of the ID2 protein was undetectable or only barely detectable, regardless of transcript expression. In both cell lines and primary tumors, ID2 expression was independent of both CDKN2A and MYCN expression. In primary neuroblastomas, CDKN1B protein was expressed in significantly fewer advanced-stage neuroblastomas than early-stage neuroblastomas, but its expression had no relationship with CDKN2A expression or MYCN amplification. We concluded that the paradoxical expression of CDKN2A in neuroblastoma cannot be explained by inactivation of the tumor-suppressor gene CDKN1B or overexpression of the oncogene ID2. We further concluded that ID2 is not a target of MYCN regulation nor is it a prognostic factor for neuroblastoma. Finally, the loss of CDKN1B in advanced-stage neuroblastoma suggests this protein may play a role in the neuroblastoma disease process.