Thymosin beta4 targeting impairs tumorigenic activity of colon cancer stem cells.

Thymosin ß4 (Tß4) is an actin-binding peptide overexpressed in several tumors, including colon carcinomas. The aim of this study was to investigate the role of Tß4 in promoting the tumorigenic properties of colorectal cancer stem cells (CR-CSCs), which are responsible for tumor initiation and growth. We first found that CR-CSCs from different patients have higher Tß4 levels than normal epithelial cells. Then, we used a lentiviral strategy to down-regulate Tß4 expression in CR-CSCs and analyzed the effects of such modulation on proliferation, survival, and tumorigenic activity of CR-CSCs. Empty vector-transduced CR-CSCs were used as a control. Targeting of the Tß4 produced CR-CSCs with a lower capacity to grow and migrate in culture and, interestingly, reduced tumor size and aggressiveness of CR-CSC-based xenografts in mice. Moreover, such loss in tumorigenic activity was accompanied by a significant increase of phosphatase and tensin homologue (PTEN) and a concomitant reduction of the integrin-linked kinase (ILK) expression, which resulted in a decreased activation of protein kinase B (Akt). Accordingly, exogenous expression of an active form of Akt rescued all the protumoral features lost after Tß4 targeting in CR-CSCs. In conclusion, Tß4 may have important implications for therapeutic intervention for treatment of human colon carcinoma.

Presence of anaplastic lymphoma kinase in inflammatory breast cancer.

Although Inflammatory Breast Cancer (IBC) is recognized as the most metastatic variant of locally advanced breast cancer, the molecular basis for the distinct clinical presentation and accelerated program of metastasis of IBC is unknown. Reverse phase protein arrays revealed activation of the receptor tyrosine kinase, anaplastic lymphoma kinase (ALK) and biochemically-linked downstream signaling molecules including JAK1/STAT3, AKT, mTor, PDK1, and AMPKß in pre-clinical models of IBC. To evaluate the clinical relevance of ALK in IBC, analysis of 25 IBC patient tumors using the FDA approved diagnostic test for ALK genetic abnormalities was performed. These studies revealed that 20/25 (80%) had either increased ALK copy number, low level ALK gene amplification, or ALK gene expression, with a prevalence of ALK alterations in basal-like IBC. One of 25 patients was identified as having an EML4-ALK translocation. The generality of gains in ALK copy number in basal-like breast tumors with IBC characteristics was demonstrated by analysis of 479 breast tumors using the TGCA data-base and our newly developed 79 IBC-like gene signature. The small molecule dual tyrosine kinase cMET/ALK inhibitor, Crizotinib (PF-02341066/Xalkori®, Pfizer Inc), induced both cytotoxicity (IC50 = 0.89 µM) and apoptosis, with abrogation of pALK signaling in IBC tumor cells and in FC-IBC01 tumor xenograft model, a new IBC model derived from pleural effusion cells isolated from an ALK(+) IBC patient. Based on these studies, IBC patients are currently being evaluated for the presence of ALK genetic abnormalities and when eligible, are being enrolled into clinical trials evaluating ALK targeted therapeutics.