Linda Steelman - Academia.edu (original) (raw)

Papers by Linda Steelman

PubMed, Mar 1, 2003

The Ras/Raf/MEK/ERK signal transduction pathway regulates cell cycle progression and apoptosis in... more The Ras/Raf/MEK/ERK signal transduction pathway regulates cell cycle progression and apoptosis in diverse types of cells. Mutations in this pathway are often observed in transformed cell lines and frequently linked with human cancers. The Ras/Raf/MEK/ERK pathway can induce events both associated with cell proliferation and cell cycle arrest. The particular course chosen may depend on the strength and the particular Raf gene activated by Ras. This pathway also is involved in maintaining cell survival by modulating the activity of apoptotic molecules including Bad and Bcl-2. This review will discuss the regulation of the Ras/Raf/MEK/ERK pathway and how it modulates cell cycle progression and cell survival.

Advances in biological regulation, Aug 1, 2020

The COVID-19 pandemic has put a serious strain on health treatments as well at the economies of m... more The COVID-19 pandemic has put a serious strain on health treatments as well at the economies of many nations. Unfortunately, there is not currently available vaccine for SARS-Cov-2/COVID-19. Various types of patients have delayed treatment or even routine checkups and we are adapting to a virtual world. In many cases, surgeries are delayed unless they are essential. This is also true with regards to cancer treatments and screening. Interestingly, some existing drugs and nutraceuticals have been screened for their effects on COVID-19. Certain FDA approved drugs, vitamin, natural products and trace minerals may be repurposed to treat or improve the prevention of COVID-19 infections and disease progression. This review article will summarize how the treatments of various cancer patients has changed during the COVID-19 era as well as discuss the promise of some existing drugs and other agents to be repurposed to treat this disease.

Cells

Approximately 90% of pancreatic cancers are pancreatic ductal adenocarcinomas (PDAC). PDAC is the... more Approximately 90% of pancreatic cancers are pancreatic ductal adenocarcinomas (PDAC). PDAC is the fourth leading cause of cancer death world-wide. Therapies for PDAC are largely ineffective due to the dense desmoplastic tumor microenvironment which prevents chemotherapeutic drugs and small molecule inhibitors from exerting effective anti-cancer effects. In this review, we will discuss the roles of TP53 and miRs on the PDAC tumor microenvironment and how loss of the normal functions of TP53 promote tumor progression. The TP53 gene is mutated in approximately 50% of pancreatic cancers. Often, these TP53 mutations are point mutations which confer additional functions for the TP53 proteins. These are called gain of function (GOF) mutations (mut). Another class of TP53 mutations are deletions which result in loss of the TP53 protein; these are referred to TP53-null mutations. We have organized this review into various components/properties of the PDAC microenvironment and how they may be...

Cells, 2022

The TP53 tumor suppressor is mutated in ~75% of pancreatic cancers. The mutant TP53 protein in pa... more The TP53 tumor suppressor is mutated in ~75% of pancreatic cancers. The mutant TP53 protein in pancreatic ductal adenocarcinomas (PDAC) promotes tumor growth and metastasis. Attempts have been made to develop molecules that restore at least some of the properties of wild-type (WT) TP53. APR-246 is one such molecule, and it is referred to as a mutant TP53 reactivator. To understand the potential of APR-246 to sensitize PDAC cells to chemotherapy, we introduced a vector encoding WT-TP53 into two PDAC cell lines, one lacking the expression of TP53 (PANC-28) and one with a gain-of-function (GOF) mutant TP53 (MIA-PaCa-2). APR-246 increased drug sensitivity in the cells containing either a WT or mutant TP53 protein with GOF activity, but not in cells that lacked TP53. The introduction of WT-T53 into PANC-28 cells increased their sensitivity to the TP53 reactivator, chemotherapeutic drugs, and signal transduction inhibitors. The addition of WT-TP53 to PDAC cells with GOF TP53 also increase...

Biomolecules, 2022

Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic cancer. In ~75% of ... more Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic cancer. In ~75% of PDAC, the tumor suppressor TP53 gene is mutated. Novel approaches to treat cancer involve compounds called mutant TP53 reactivators. They interact with mutant TP53 proteins and restore some of their growth suppressive properties, but they may also interact with other proteins, e.g., TP63 and TP73. We examined the ability of the TP53 reactivator APR-246 to interact with eleven modified berberine compounds (NAX compounds) in the presence and absence of WT-TP53 in two PDAC cell lines: the MIA-PaCa-2, which has gain of function (GOF) TP53 mutations on both alleles, and PANC-28, which lacks expression of the WT TP53 protein. Our results indicate the TP53 reactivator-induced increase in therapeutic potential of many modified berberines.

Blood, 2004

v-ErbB is an oncogene related to the Epidermal Growth Factor Receptor (EGF-R) that was initially ... more v-ErbB is an oncogene related to the Epidermal Growth Factor Receptor (EGF-R) that was initially discovered in the genome of avian erythoblastosis virus. v-ErbB will abrogate the requirement of erythroid progenitor cells for erythropoietin and stem cell factor and block terminal differentiation. EGF-R overexpression has been observed in many pathological situations and the EGF-R gene is amplified in certain tumors. Moreover, there is a truncated form of EGF-R referred to as EGFvIII which resembles v-ErbB in biological properties. One problem frequently encountered in studying the effects of EGF-R overexpression in many tumors is that EGF-R expression is often constitutive and in the presence of increased expression of other oncogenes or in the absence of certain tumor suppressor genes. To circumvent these problems, we subcloned v-ErbB into a vector which contained the estrogen receptor hormone binding domain which renders the v-ErbB protein dependent upon the addition of beta-estrad...

Blood, 2008

In hematologic malignancies, constitutive activation of the Raf/MEK/ERK pathway is frequently obs... more In hematologic malignancies, constitutive activation of the Raf/MEK/ERK pathway is frequently observed, conveys a poor prognosis, and constitutes a promising target for therapeutic intervention. Indeed, we have recently demonstrated that selective MEK-I potently inhibit the growth of AML cell lines and ex vivo-cultured primary AML blasts (Blood2006, 108:254). However, these effects are mostly related to the inhibition of cell cycle progression, while apoptosis induction requires higher concentrations of the inhibitors and longer times of exposure. Thus, we investigated MEK-I-induced changes in phospho-protein expression and gene expression profiles, in order to identify relevant downstream targets and to design rational MEK-I-based combination strategies. Analysis of phosphorylation levels of 18 different target proteins performed in OCI-AML3 cells indicated that MEK blockade induces, among other effects, an over-activation of RAF and MEK, suggesting the interruption of a negative f...

Blood, 2007

The roles of signaling and apoptotic pathways in apoptosis and drug resistance of p53 wild-type (... more The roles of signaling and apoptotic pathways in apoptosis and drug resistance of p53 wild-type (WT) hematopoietic cells were investigated in cytokine-dependent early myeloid (FL5.12) and Flt-3 mutant AML (MOLM-13) cells. Drug resistant lines were isolated by limiting dilution in doxorubicin, a drug frequently used in AML therapy. Drug resistant FL/Doxo cells had higher levels of activated Raf/MEK/ERK and PI3K/Akt signaling than parental FL5.12 cells as 5.4-, 6.8-, and 3-fold more active MEK, ERK and Akt respectively were detected upon doxorubicin treatment whereas similar levels were detected in the absence of doxorubicin. The increased levels of activated MEK, ERK and Akt were essential for their drug resistance as MEK and mTOR inhibitors eliminated drug resistance. Introduction of dominant negative (DN) MEK1 increased drug sensitivity of FL5.12 and FL/Doxo cells 6.8-, and 5.3-fold respectively, while introduction of constitutively-active (CA) MEK1 increased resistance 2.5-, and 5...

Advances in Biological Regulation, 2018

Advances in biological regulation, 2018

Neutrophil gelatinase-associated lipocalin (NGAL a.k.a lipocalin 2, lnc2) is a secreted protein w... more Neutrophil gelatinase-associated lipocalin (NGAL a.k.a lipocalin 2, lnc2) is a secreted protein which can form a complex with matrix metalloproteinase-9 (MMP9). This MMP9/NGAL complex has been associated with metastasis. MMP9 and NGAL are detected in the urine of patients afflicted with many different types of cancer, including prostate cancer. The effects of p53, NF-κB and the androgen receptor (AR) on the expression of NGAL was examined in four prostate cancer cell lines. Prostate cancer cell lines that are AR negative and expressed either mutant or no p53 (DU145 and PC3) displayed higher levels of NGAL expression compared to the prostate cancer cell lines (LNCaP and 22Rv-1) which are AR positive and express wild type (WT) p53. Introduction of WT-p53 into the PC3 prostate cancer cell line, resulted in reduction of the levels of NGAL expression. Conversely, introduction of dominant negative (DN) p53 or a retroviral construct expressing NF-κB into LNCaP cells increased NGAL expressi...

International Journal of Oncology, 2003

Epidermal growth factor (EGF) receptors (EGFRs) and signaling pathways activated by these recepto... more Epidermal growth factor (EGF) receptors (EGFRs) and signaling pathways activated by these receptors have been associated with development of breast cancer as well as its resistance to treatment with cytotoxic drugs. This review describes the current understanding of EGFRs and their downstream signaling pathways. Emphasis is placed upon Raf/MEK/ERK and PI3K/PDK1/Akt signaling pathways and their relationship to regulation of apoptosis and cell cycle progression. Also discussed is the relationship between these signaling pathways and response of breast cancer to chemotherapeutic treatment. An appreciation of how these signaling pathways relate to development of breast cancer and its response to chemotherapy may lead to improved prevention, diagnosis, and treatment of this disease. Contents 1. Introduction 2. EGFRs and EGFR ligands 3. Signaling pathways activated by EGFRs 4. Modulation of transcription factor activity by EGFR signaling 5. Regulation of apoptosis by EGFR signaling 6. Cell cycle control by EGFR signaling 7. Relationship between EGFR signaling and development of breast cancer 8. Breast cancer chemotherapy 9. Effects of EGFR signaling on chemotherapeutic drug resistance 10. Conclusions

Oncotarget, 2012

The Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades are often activated by genetic alterations in... more The Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR cascades are often activated by genetic alterations in upstream signaling molecules such as receptor tyrosine kinases (RTK). Certain components of these pathways, RAS, NF1, BRAF, MEK1, DUSP5, PP2A, PIK3CA, PIK3R1, PIK3R4, PIK3R5, IRS4, AKT, NFKB1, MTOR, PTEN, TSC1, and TSC2 may also be activated/inactivated by mutations or epigenetic silencing. Upstream mutations in one signaling pathway or even in downstream components of the same pathway can alter the sensitivity of the cells to certain small molecule inhibitors. These pathways have profound effects on proliferative, apoptotic and differentiation pathways. Dysregulation of components of these cascades can contribute to: resistance to other pathway inhibitors, chemotherapeutic drug resistance, premature aging as well as other diseases. This review will first describe these pathways and discuss how genetic mutations and epigenetic alterations can result in resistance to various inhibitors.

Proceedings of the National Academy of Sciences, 1989

Stearic acid is toxic for T lymphocytes in vitro but has little effect on B lymphocytes. To inves... more Stearic acid is toxic for T lymphocytes in vitro but has little effect on B lymphocytes. To investigate the molecular basis for this difference, purified murine T and B lymphocytes were compared for their abilities to incorporate and metabolize stearic acid. Unstimulated T and B cells incorporated identical amounts of stearic acid into six different phospholipids and four neutral lipids. After mitogen stimulation, fatty acid uptake was increased in both lymphocyte types, but cell-specific differences were seen in the distribution of stearic acid among the various cellular lipids. Doses of stearic acid that selectively inhibited T-cell proliferation resulted in a 5-fold greater accumulation of distearoylphosphatidylcholine in T cells than in B cells. Whereas T cells did not desaturate the exogenously derived stearic acid, up to 25% of the saturated fatty acid was converted to oleic acid in B cells. These findings suggested a deficiency of stearoyl-CoA desaturase (acyl-CoA, hydrogen-d...

Leukemia, 2004

The roles of the JAK/STAT, Raf/MEK/ERK and PI3K/Akt signal transduction pathways and the BCR-ABL ... more The roles of the JAK/STAT, Raf/MEK/ERK and PI3K/Akt signal transduction pathways and the BCR-ABL oncoprotein in leukemogenesis and their importance in the regulation of cell cycle progression and apoptosis are discussed in this review. These pathways have evolved regulatory proteins, which serve to limit their proliferative and antiapoptotic effects. Small molecular weight cell membrane-permeable drugs that target these pathways have been developed for leukemia therapy. One such example is imatinib mesylate, which targets the BCR-ABL kinase as well as a few structurally related kinases. This drug has proven to be effective in the treatment of CML patients. However, leukemic cells have evolved mechanisms to become resistant to this drug. A means to combat drug resistance is to target other prominent signaling components involved in the pathway or to inhibit BCR-ABL by other mechanisms. Treatment of imatinib-resistant leukemia cells with drugs that target Ras (farnysyl transferase inhibitors) or with the protein destabilizer geldanamycin has proven to be a means to inhibit the growth of resistant cells. This review will tie together three important signal transduction pathways involved in the regulation of hematopoietic cell growth and indicate how their expression is dysregulated by the BCR-ABL oncoprotein.

Leukemia, 2003

Novel approaches have been designed to treat leukemia based on our understanding of the genetic a... more Novel approaches have been designed to treat leukemia based on our understanding of the genetic and biochemical lesions present in different malignancies. This meeting report summarizes some of the recent advances in leukemia treatment. Based on the discoveries of cellular oncogenes, chromosomal translocations, monoclonal antibodies, multidrug resistance pumps, signal transduction pathways, genomics/proteonomic approaches to clinical diagnosis and mutations in biochemical pathways, clinicians and basic scientists have been able to identify the particular genetic mutations and signal transduction pathways involved as well as design more appropriate treatments for the leukemia patient. This meeting report discusses these exciting new therapies and the results obtained from ongoing clinical trials. Furthermore, rational approaches to treat complications of tumor lysis syndrome by administration of the recombinant urate oxidase protein, also known as rasburicase, which corrects the biochemical defect present in humans, were discussed. Clearly, over the past 25 years, molecular biology and biotechnology has provided the hematologist/oncologist novel bullets in their arsenal that will allow treatment by design in leukemia.

Leukemia, 2008

Mutations and chromosomal translocations occur in leukemic cells that result in elevated expressi... more Mutations and chromosomal translocations occur in leukemic cells that result in elevated expression or constitutive activation of various growth factor receptors and downstream kinases. The Raf/MEK/ERK, PI3K/PTEN/Akt/mTOR and Jak/STAT pathways are often activated by mutations in upstream genes. The Raf/MEK/ERK and PI3K/PTEN/Akt/mTOR pathways are regulated by upstream Ras that is frequently mutated in human cancer. Recently, it has been observed that the FLT-3 and Jak kinases and the phosphatase and tensin homologue deleted on chromosome 10 (PTEN) phosphatase are also frequently mutated or their expression is altered in certain hematopoietic neoplasms. Many of the events elicited by the Raf/MEK/ERK, PI3K/PTEN/Akt/mTOR and Jak/STAT pathways have direct effects on survival pathways. Aberrant regulation of the survival pathways can contribute to uncontrolled cell growth and lead to leukemia. In this review, we describe the Raf/MEK/ ERK, PI3K/PTEN/Akt/mTOR and Jak/STAT signaling cascades and summarize recent data regarding the regulation and mutation status of these pathways and their involvement in leukemia.