A quantitative study on the growth variability of tumour cell clones in vitro

Objectives: In this study, we quantify the growth variability of tumour cell clones from a human leukemia cell line. Materials and methods: We have used microplate spectrophotometry to measure the growth kinetics of hundreds of individual cell clones from the Molt3 cell line. The growth rate of each clonal population has been estimated by fitting experimental data with the logistic equation. Results: The growth rates were observed to vary among different clones. Up to six clones with a growth rate above or below the mean growth rate of the parent population were further cloned and the growth rates of their offsprings were measured. The distribution of the growth rates of the subclones did not significantly differ from that of the parent population thus suggesting that growth variability has an epigenetic origin. To explain the observed distributions of clonal growth rates we have developed a probabilistic model assuming that the fluctuations in the number of mitochondria through successive cell cycles are the leading cause of growth variability. For fitting purposes, we have estimated experimentally by flow cytometry the maximum average number of mitochondria in Molt3 cells. The model fits nicely the observed distributions of growth rates, however, cells in which the mitochondria were rendered non functional (rho-0 cells) showed only a 30% reduction in the clonal growth variability with respect to normal cells. Conclusions: A tumor cell population is a dynamic ensemble of clones with highly variable growth rate. At least part of this variability is due to fluctuations in the number of mitochondria.Comment: 31 pages, 5 figure

MEK1/2 regulate normal BCR and ABL1 tumor-suppressor functions to dictate ATO response in TKI-resistant Ph+ leukemia

Resistance to tyrosine kinase inhibitors (TKIs) remains a clinical challenge in Ph-positive variants of chronic myeloid leukemia. We provide mechanistic insights into a previously undisclosed MEK1/2/BCR::ABL1/BCR/ABL1-driven signaling loop that may determine the efficacy of arsenic trioxide (ATO) in TKI-resistant leukemic patients. We find that activated MEK1/2 assemble into a pentameric complex with BCR::ABL1, BCR and ABL1 to induce phosphorylation of BCR and BCR::ABL1 at Tyr360 and Tyr177, and ABL1, at Thr735 and Tyr412 residues thus provoking loss of BCR's tumor-suppression functions, enhanced oncogenic activity of BCR::ABL1, cytoplasmic retention of ABL1 and consequently drug resistance. Coherently, pharmacological blockade of MEK1/2 induces dissociation of the pentameric MEK1/2/BCR::ABL1/BCR/ABL1 complex and causes a concurrent BCRY360/Y177, BCR::ABL1(Y360/Y177) and cytoplasmic ABL1(Y412/T735) dephosphorylation thereby provoking the rescue of the BCR's anti-oncogenic activities, nuclear accumulation of ABL1 with tumor-suppressive functions and consequently, growth inhibition of the leukemic cells and an ATO sensitization via BCR-MYC and ABL1-p73 signaling axes activation. Additionally, the allosteric activation of nuclear ABL1 was consistently found to enhance the anti-leukemic effects of the MEK1/2 inhibitor Mirdametinib, which when combined with ATO, significantly prolonged the survival of mice bearing BCR::ABL1-T315I-induced leukemia. These findings highlight the therapeutic potential of MEK1/2-inhibitors/ATO combination for the treatment of TKI-resistant leukemia

The Prostate Specific Membrane Antigen Regulates the Expression of IL-6 and CCL5 in Prostate Tumour Cells by Activating the MAPK Pathways1

The interleukin-6 (IL-6) and the chemokine CCL5 are implicated in the development and progression of several forms of tumours including that of the prostate. The expression of the prostate specific membrane antigen (PSMA) is augmented in high-grade and metastatic tumors. Observations of the clinical behaviour of prostate tumors suggest that the increased secretion of IL-6 and CCL5 and the higher expression of PSMA may be correlated. We hypothesized that PSMA could be endowed with signalling properties and that its stimulation might impact on the regulation of the gene expression of IL-6 and CCL5. We herein demonstrate that the cross-linking of cell surface PSMA with specific antibodies activates the small GTPases RAS and RAC1 and the MAPKs p38 and ERK1/2 in prostate carcinoma LNCaP cells. As downstream effects of the PSMA-fostered RAS-RAC1-MAPK pathway activation we observed a strong induction of NF-κB activation associated with an increased expression of IL-6 and CCL5 genes. Pharmacological blockade with specific inhibitors revealed that both p38 and ERK1/2 participate in the phenomenon, although a major role exerted by p38 was evident. Finally we demonstrate that IL-6 and CCL5 enhanced the proliferative potential of LNCaP cells synergistically and in a dose-dependent manner and that CCL5 functioned by receptor-mediated activation of the STAT5-Cyclin D1 pro-proliferative pathway. The novel functions attributable to PSMA which are described in the present report may have profound influence on the survival and proliferation of prostate tumor cells, accounting for the observation that PSMA overexpression in prostate cancer patients is related to a worse prognosis

RelB-Dependent Stromal Cells Promote T-Cell Leukemogenesis

BACKGROUND: The Rel/NF-kappaB transcription factors are often activated in solid or hematological malignancies. In most cases, NF-kappaB activation is found in malignant cells and results from activation of the canonical NF-kappaB pathway, leading to RelA and/or c-Rel activation. Recently, NF-kappaB activity in inflammatory cells infiltrating solid tumors has been shown to contribute to solid tumor initiation and progression. Noncanonical NF-kappaB activation, which leads to RelB activation, has also been reported in breast carcinoma, prostate cancer, and lymphoid leukemia. METHODOLOGY/PRINCIPAL FINDINGS: Here we report a novel role for RelB in stromal cells that promote T-cell leukemogenesis. RelB deficiency delayed leukemia onset in the TEL-JAK2 transgenic mouse model of human T acute lymphoblastic leukemia. Bone marrow chimeric mouse experiments showed that RelB is not required in the hematopoietic compartment. In contrast, RelB plays a role in radio-resistant stromal cells to accelerate leukemia onset and increase disease severity. CONCLUSIONS/SIGNIFICANCE: The present results are the first to uncover a role for RelB in the crosstalk between non-hematopoietic stromal cells and leukemic cells. Thus, besides its previously reported role intrinsic to specific cancer cells, the noncanonical NF-kappaB pathway may also play a pro-oncogenic role in cancer microenvironmental cells

T cell adhesion and cytolysis of pancreatic cancer cells: a role for E-cadherin in immunotherapy?

Pancreatic cancer is an aggressive and potent disease, which is largely resistant to conventional forms of treatment. However, the discovery of antigens associated with pancreatic cancer cells has recently suggested the possibility that immunotherapy might become a specific and effective therapeutic option. T cells within many epithelia, including those of the pancreas, are known to express the αEβ7-integrin adhesion molecule, CD103. The only characterised ligand for CD103 is E-cadherin, an epithelial adhesion molecule which exhibits reduced expression in pancreatic cancer. In our study, CD103 was found to be expressed only by activated T cells following exposure to tumour necrosis factor beta 1, a factor produced by many cancer cells. Significantly, the expression of this integrin was restricted mainly to class I major histocompatibility complex-restricted CD8+ T cells. The human pancreatic cancer cell line Panc-1 was transfected with human E-cadherin in order to generate E-cadherin negative (wild type) and positive (transfected) sub-lines. Using a sensitive flow cytometric adhesion assay it was found that the expression of both CD103 (on T cells) and E-cadherin (on cancer cells) was essential for efficient adhesion of activated T cells to pancreatic cancer cells. This adhesion process was inhibited by the addition of antibodies specific for CD103, thereby demonstrating the importance of the CD103→E-cadherin interaction for T-cell adhesion. Using a 51Cr-release cytotoxicity assay it was found that CD103 expressing T cells lysed E-cadherin expressing Panc-1 target cells following T cell receptor stimulation; addition of antibodies specific for CD103 significantly reduced this lysis. Furthermore, absence of either CD103 from the T cells or E-cadherin expression from the cancer cells resulted in a significant reduction in cancer cell lysis. Therefore, potentially antigenic pancreatic cancer cells could evade a local anti-cancer immune response in vivo as a consequence of their loss of E-cadherin expression; this phenotypic change may also favour metastasis by reducing homotypic adhesion between adjacent cancer cells. We conclude that effective immunotherapy is likely to require upregulation of E-cadherin expression by pancreatic cancer cells or the development of cytotoxic immune cells that are less dependent on this adhesion molecule for efficient effecter function

Adult T-cell acute lymphoblastic leukemia: prognostic impact of myeloid associated antigens.

valuation of: Khabori M, Samiee S, Fung S et al. Adult precursor T-lymphoblastic leukemia/lymphoma with myeloid-associated antigen expression is associated with a lower complete remission rate following induction chemotherapy. Acta Haematol. 120, 5\u201310 (2008). Despite the recent improvement in the treatment of the disease, the prognosis of adult T-cell acute lymphoblastic leukemia (T-ALL) remains poor. In the last several decades, many reports analyzed clinical and/or biological factors in order to identify prognostic parameters suitable for risk stratification of T-ALL patients. The article under review analyzed the prognostic impact of myeloid-associated antigen expression in a monocentric cohort of adult T-ALL patients

Intracellular zinc increase inhibits p53(-/-) pancreatic adenocarcinoma cell growth by ROS/AIF-mediated apoptosis

We show that treatment with non-toxic doses of zinc in association to the ionophore compound pyrrolidine dithiocarbamate (PDTC) inhibits p53(-/-) pancreatic cancer cell growth much more efficiently than gemcitabine, the gold standard chemotherapeutic agent for pancreatic cancer. Both the metal chelator N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine and the radical scavenger N-acetyl-l-cysteine are able to recover cell growth inhibition by Zn/PDTC, demonstrating that this effect depends on the increased levels of intracellular zinc and of reactive oxygen species (ROS). Zn/PDTC treatment induces a strong apoptotic cell death that is associated to ROS-dependent nuclear translocation of the mitochondrial factor AIF, but not to the regulation of apoptotic genes and caspase activation. Primary fibroblasts are more resistant than pancreatic cancer cells to Zn/PDTC treatment and exhibit a lower basal and Zn/PDTC-induced enhancement of intracellular zinc. We show that Zn/PDTC induces p53 proteasomal degradation and that the proteasome inhibitor MG132 further increases fibroblast growth inhibition by Zn/PDTC, suggesting that p53 degradation plays an important role in fibroblast resistance to Zn/PDTC