| 2017 | 2016 | 2015 |
Treatment of breast cancer has typically revolved around the use of chemotherapy and endocrine therapy, but these treatments aren't always effective, especially depending on the type of breast cancer. Some luminal B cancers are fairly unresponsive to the standard treatment, with high instances of relapse. These cancers are characterized by increased levels of Ki-67, which is a protein that activates mitosis. Currently patients with luminal B cancer face a poor prognosis and scientists are trying to more specifically target certain types of cancer to improve tumor responsiveness.
BCL-2 proteins promote survival of cells and are typically found in high numbers in breast cancer cells. It is found in 85% of estrogen receptor (ER) positive (over express estrogen receptors and are more mitotically active) breast cancer. BCL-2 is responsive to estrogenís presence and inhibits the cell from undergoing apoptosis. In this study researchers targeted a variety of pro survival pathways (BCL-2 and PI3K/mTOR pathways) in cancer cells from xenografts with BH3 mimetics. BH3 mimetics are small molecule inhibitors (ex: BIM) that mimic the action of proapoptotic ìBH3-only proteinsî which in vivo binds to the BCL-2 proteins and stop the survival pathway from progressing. Two BH3 mimetics that have been widely studied are ABT-737 and ABT-263 (also known as navitoclax) which functions by binding to the pro-survival proteins BCL-2, BCL-XL, and BCL-W (not MCL-1 or A1) neutralizing them. In previous studies these BH3 molecules have been shown to be successful in reducing cancer when combined with cytotoxic therapy. However both ABT-737 and ABT-263 have been previously shown to cause thrombocytopenia (reduction in blood platelet number) and neutropenia (reduction in neutrophil number). ABT-737 was found to target only BCL-2 proteins.
ABT-199 is a BHC mimetic that researchers have not yet studied in breast cancer. It has recently been developed and is recognized for its platelet sparing properties which provides a promising solutions for cancer therapy. In this study they tested ABT-199 and ABT-737 in order to characterize their potential role in fighting breast cancer. They first found that BCL-2 was over-expressed in luminal B subtypes from genetic analysis of 2000 breast cancer genome sets. They then developed tumor xenografts by transplanting tissues different variations of breast cancer tissues into severely immunocompromised mice. These in-vivo tumors provide significant advantages over cell line based xenografts. The ER positive xenograft models (23T, 31T, and 50T) corresponded to the luminal B subtype based on their Ki-67 expression. They also have high BCL-XL levels. They found that ABT 737 and ABT 199 could enhance responsiveness to tamoxifen in all positive ER tumors, with complete tumor regression in 23T. In the 315T and 50T models, combination therapy with tamoxifen and ABT 737 and 199 had equal effectiveness in delaying tumor growth. The mice maintained normal body weight throughout the experiment. They found that ABT-199 did not reduce endometrial diameter indicating some potential drawbacks in its use.
Two xenograft models (315T and 50T) had higher levels of pAKT than the responsive 23T xenograft. AKT is associated with resistance to tamoxifen-induced apoptosis. The researchers decided to test whether targeting another pro-survival pathway would create the same effect. They used AZD8055, a P13K/mTOR inhibitor and found that the combined treatment with ABT 737 induced rapid cell death, but individual agents did very little. They found that mTOR inhibition also seemed to increase BCL-2 expression and decreased level of phosphorylated BAD which activates it. The BCL-2/BAD complexes increased the cells susceptibility to BH3 mimetics so the combination of both BH3 mimetics and mTOR inhibitors could provide a potential solution to breast cancers with high levels of BCL-2 and AKT levels. Overall, they recommended combinations of BH3 mimetics, specifically ABT199, mTOR inhibitors, and endocrine therapy, when targeting breast cancer, especially for tumors that have previously had a poor prognosis.
Links related to the paper:
The BCL-2 arbiters of apoptosis and their growing role as cancer targets
Deciphering the rules of programmed cell death to improve therapy of cancer and other diseases
Current development of the second generation of mTOR inhibitors as anticancer agents
ABT-199: Taking Dead Aim at BCL-2
Epithelial ovarian cancer (EOC) is a common cause of cancer death in women, with a five-year survival rate below 45%. Most cases are found at an advanced stage and therefore present the highest fatality rates for gynecologic malignancies.
This experiment explores the possibility of breast cancer metastasis-suppressor 1-like (BRMS1L) as a tumor suppressor gene in EOC and its metastasis. In a 2014 paper by Chang Gong et al., BRMS1L downregulation is correlated with a worse prognosis in breast cancer patients. This paper explores whether or not this gene, when upregulated in EOC, suppresses progression and/or metastasis.
Because the Wnt signaling pathway is highly involved in cell proliferation and apoptosis, the activation of this pathway and upregulation of β-catenin is closely linked to cancer progression. This activation of the Wnt pathway directly activates epithelial to mesenchymal transition (EMT) which is a primary mechanism for metastasis. The presence of metastasis, for most cancers, complicates the prognosis and survival rates of those diagnosed with cancer, so it is important to find a way to prevent metastasis initially.
Links related to the paper:
How BRMS1L acts in Breast Cancer
Overview of Epithelial Ovarian Cancer
Wnt Signaling in Ovarian Cancer
Epithelial to Mesenchymal Transition in EOC
Colorectal cancer is one of the deadliest types of cancer worldwide especially since it is often diagnosed during the later stages. This paper proposes a treatment that targets the VEGF-related pathway and EGFR. Cetuximab is an anti-EGFR monoclonal antibody that can be used to overcome anti-EGFR resistance. However, it is possible that cetuximab cannot block EGFR completely in cancer treatment because other growth factors and receptors can be activated in the cancer cell to proceed in alternate pathways besides EGFR. Regorafenib is an oral multi-kinase inhibitor that can target other oncogenic pathways. Regorafenib has exhibited antitumor activity, so the researchers decided to test the effects of administering Regorafenib, Cetuximab, and a combination of the two to overcoming resistance to anti-EGFR mAbs.
Five cancer cell lines with the KRAS mutation were selected to test because a possible mechanism that allows for resistance to cetuximab includes mutations in the KRAS gene. Two other cancer cell lines with the acquired resistance to cetuximab were used. Cetuximab, regorafenib, and the combination of the two would be tested against these cells in vivo and in vitro and the results were published in this paper. The in vivo tests included injecting mice with tumors, growing the tumors in vivo and then administering the drugs or combination of the drugs orally.
Combining cetuximab and regorafenib led to antiproliferation and apoptosis of tumor cells in cetuximab-resistant cell lines. This was accomplished by blocking MAPK and AKT pathways which both involve cell proliferation. Even after tumors were grown in vivo, the combined treatment induced tumor growth that was much less severe and prevented metastasis formation.
Links related to the paper:
Cetuximab for the treatment of colorectal cancer
Regorafenib treatment for colorectal cancer
More on RAS mutation and anti-EGFR mAb
Focal adhesion kinase (FAK) is responsible for controlling multiple adhesion dependent cellular functions such as migration, proliferation, and survival. A main sign of cancerous cells is the loss of positional control over growth and survival. FAK is a tyrosine kinase that is found at sights of integrin mediated cell adhesion to the extracellular matrix, which is overexpressed in metastatic tumors and promotes further cancer invasion. FAK can also be found at elevated levels in cancers that have not yet become invasive.
Little is known about the role of FAK during the early stages of tumorigenesis. Transformed mammary epithelial cells (MECs) are responsible for breast cancer initiation. The authors of this article studied the effect of FAK activation in non-transformed MECs to understand how it affects tumor initiation. It was found that FAK activation functions as expected in 2D-culture. However, in 3D-cultures, which more accurately represent tissue morphology, it was found that mammary cells respond to FAK activation by suppression of apoptosis, promoting morphogenesis.
This is a modified function of FAK because deep-tissue FAK signaling is not required for normal morphogenesis. Therefore, the authors hypothesis that FAK activation may play a role in tumor initiation by causing a resistance to apoptosis. FAK activation in breast epithelial cells could be dependent on the tissue it is connected to.
Links related to the paper:
Supression of Apoptosis in Mammary Epithelial Cells (MECs)
Integrin-mediated adhesion and signaling in tumorigenesis
This experiment investigated the role of SOX9 in the regulation of wnt signaling in colorectal cancer cells. SOX9 was found to transport beta catenin out of the nucleus to the cytosol so it could not bind to the transcription factor and there would be limited proliferation of the CRC cells. In DLD-1 CRC cells there has been an observed increase in what researchers thought was SOX9; inconsistent with what was known about SOX9ís involvement in CRC. MiniSox9 was the variant form of the SOX9 detected in the DLD-1 CRC cells. MiniSOX9 is missing the C-terminus of SOX 9, yet preserves the same key coding sequence unique to SOX9 only (not seen in SOX8 or SOX10). This unique coding sequence was known as short SOX9 sequence (S9pep).
It was flagged with the SV40 T-Antigen to create two nuclear localization signals before being cloned into a vector. The researchers then utilized doxycycline to induce the expression of S9pep in CRC cells. They found that the phenotype of unmutated SOX9 was rescued and the effects of MiniSOX9 reversed. This experiment was then repeated in mice in which similar results were observed. Thus providing a stepping stone for the development of a peptide based therapeutic approach to recusing DLD-1 CRC.
Links related to the paper:
SOX9 Stem-Cell Factor: Clinical and Functional Relevance in Cancer
NLS-tagging: an alternative strategy to tag nuclear proteins
Tet-On Systems For Doxycycline-inducible Gene Expression.
Glioblastoma (GBM) is a lethal cancer found in the brain, and therefore is a target of cancer research. Mutations in glioma stem cells can lead to this cancer. It has been found that dysregulation of various components of the Wnt signaling pathway are a leading cause of glioblastoma. This paper shows the prevalence of the over-expression of two ligands in the Wnt pathway found in GBM tumors.
These two ligands, Wnt1 and Wnt3a were found in concentrations that were graded across tumors. There was also over-expression of Wnt1 and Wnt3a found in the glioma stem cells. This is indicative that Wnt signaling, specifically these two ligands, is crucial in the development of this type of cancer. To show the extent of the differences between healthy and mutated cell types, scientists examined two lines of glioma stem cells (HNGC-2 and NSG-K16). Both of these cell lines showed when over expression of the Wnt signaling pathway occurred, β-catenin would accumulate in the cell as well as Wnt-associated transcription factors.
To show these results, four different short-hairpin RNAs (shRNA) were used per ligand. These shRNAs were used to knock down the expression of the ligands via RNAi. By knocking down the gene, there was a decrease in Wnt ligand expression. There was also less accumulation of β-catenin, as well as decreased presence of Wnt-associated transcription factors such as c-Myc and CyclinD1. Decreased expression of these Wnt components led to decreased cell proliferation as well as malignancy. These studies led researchers to believe new GBM therapies should focus on targeting Wnt signaling.
Links related to the paper:
Wnt Signaling in GBM and Therapeutics
Lin-3 is the only observed Epidermal Growth Factor (EGF) found in C. elegans. It functions in various Receptor Tyrosine Kinase (RTK) pathways for various developmental processes. An example of this is vulval formation. In this scenario, anchor cells secrete Lin-3 to induce differential gene expression in adjacent vulval precursor cells that would eventually lead to the formation of the vulva. This example serves as one of many ways that Lin-3 induces C. elegans development.
Hang-Shiang Jiang and Yi-Chun Wu report Lin-3 contribution towards apoptosis during C. elegans development. Lin-3 mutants were reported to have fewer cell deaths occur during various stages in embryonic development. In addition, Let-23 mutants as well as the Lin-3; Let-23 double mutants were reported to have a similar number of cell deaths. This indicates that Lin-3 is acting through an RTK pathway in order to induce cell death.
Lin-3 is believed to induce cell death by activating expression of egl-1, an essential gene in the core programmed cell death pathway. This is done by phosphorylating Lin-1, a transcription factor that binds to a region on the egl-1 promoter. The discovery that Lin-3 contributes to cell death further adds to the list of activities the protein participates in. Further fine tuning of Lin-3 regulation may provide another method towards counteracting human cancer.
Links related to the paper:
Overview on C. elegans Embryonic Development
Review Paper on PCD in C. elegans
More Information about PCD in C. elegans
Throughout history, there are a number of gaps within the fossil record of scleractinian coral. The suggested reasoning behind these gaps is the plasticity of coral to have either soft or calcified bodies. With a soft body, they would leave behind no fossil record. This experiment tests these hypotheses by exposing coral species to reduced levels of pH that would be similar to ocean acidification through time. Analyzing tissue specific responses, researchers look into the role of programmed cell death mechanisms.
By placing two species of coral (Pocillopora damicornis and Oculina patagonica) into reduced pH conditions (pH 7.2), apoptosis was induced, and the polyps dissociated from the coenosarcs. These mechanisms ultimately translate to the loss of coloniality within the coral. Once returned to normal pH, the calcification resumed as coenosarcs began to regenerate. These results in response to reduced pH suggest that regulation of coloniality is done by the polyps.
By following the survival of coral through different periods of unfavorable calcification conditions, such as low pH, it is possible that this is due to their ability to alternate between a calcifying colonial form and a soft body form. By continuing research to identify the mechanisms behind these responses, deeper understandings of their survival through historically shifting environmental conditions as well as their future with the progression of climate change can be established.
Links related to the paper:
More on Plasticity: Clonal Variation for Phenotypic Plasticity in the Coral Madracis mirabilis
More on Ocean Acidification: Coral Reefs Under Rapid Climate Change and Ocean Acidification
More on Apoptosis (in general): Apoptosis Signaling
Many chemotherapeutic drugs design to treat cancer are Microtubule interfering agents (MIAs). In order to suppress the inhibition of natural apoptosis, MIAs activate mitotic arrest in cells, leading to apoptosis. Microtubules, when they are damaged, or arrested, induce signals that are involved in initiating cell death. The stage or alignment of these microtubules depends on what stage of the cell cycle cells are in. Cyclin-dependent kinase 1 (CDK1) plays a key role in regulating the cell cycle. CDK1 regulates mitotic onset, and is required for cells to enter into S-phase of mitosis.
If a cell's microtubules become destabilized, the cell cycle stops, and this is immediately followed by apoptosis, via the mitochondria-dependent pathway. This pathway is mediated by members of the Bcl-2/Bax family proteins; the phosphorylation of Bcl-2/Bax family proteins induces apoptosis via MIAs. In Bcl-2, the best understood site of phosphorylation is serine 70. Another gene belonging to this family, called "Bad", may have a phosphorylation site at serine 128.
Although this family is implicated in the MIA's induced apoptosis, the exact mechanism is not very well understood. Therefore, researchers wanted to know the mechanisms involving CDK1 in mitotic arrest and apoptosis. They found that Bcl-2 serine 70 phosphorylation increases the pro-apoptotic function of Bcl-1 and that Bad serine 128 phosphorylation induces apoptosis. This demonstrates that these two genes may induce apoptosis differently. Furthermore, cell apoptosis due to MIA therapy, was caused by CDK1 imbalances from the pro and anti-apoptotic functions of Bcl-2 family proteins.
Links related to the paper:
What are Bcl-2 family proteins?
In the model organism C. elegans, researchers have been able to pinpoint the genes involved in programmed cell death. So far, they have found that 131 somatic cells undergo programmed cell death through a cascade of apoptosis factors that are initiated by the activation of EGL-1 which then binds to CED-9 and activates CED-4 and CED-3 which are important proapoptotic. proteins that initiate programmed cell death. If these two proteins are mutated, there will be surviving cells that acquire the wrong fate and will cause an accumulation of unwanted cells in the body. To further understand how cell-death mechanisms work, researchers began investigating the relationship between autophagy and cell death in somatic-cells and germ-cells during C. elegans development.
Autophagy, which means 'self-eating' is used to break down and clear out unwanted/damaged cells from the body. Autophagy is an important mechanism used during cell death and after cell death. It is a lysosome-mediated process that involves an autophagosome that delivers damaged/unwanted cells to the lysosome where they are further degraded. To understand where and how autophagy is active during programmed cell death processes, the researchers looked at the death of germ-cells in C. elegans during oogenesis. They compared the wild-type number of corpses seen after normal cell-death in germ-cells with autophagy mutant number of corpses seen after cell death in germ-cells. They found that there was no difference in the number of corpses, but when engulfment genes were mutated, there was an increase in cell corpses. This signifies that autophagy is more involved in engulfment of germ-cells and is not actually required for germ-cell death during this germ-cell process.
In the second treatment, the researchers wanted to see what happened to the germ-cells when exposed to gamma-radiation. They wanted to see how cell-death programming works when DNA is damaged, and how autophagy is involved. In wild-type worms exposed to gamma rays, the number of cell corpses has increased. In autophagy mutants after gamma-radiation exposure, the number of corpses decreased, meaning cells that were supposed to be killed were not. They also exposed the cells to other DNA damaging agents such as ethylnitrosourea (ENU), which created lesions on the DNA. It was also seen that there was a decrease in corpses in the autophagy mutant when compared to the wild-type. This proves how autophagy activity in germ cells is necessary in the execution of the cell death program.
Researchers also wanted to test how autophagy activity is involved in germ cell death and cell death in ventral cord neurons in a weak loss-of-function CED-3 mutant. CED-3 normally promotes cell death, and it was found that when CED-3 caspase activity is temporarily compromised, autophagy contributes to germ-cell death. If both CED-3 and autophagy are mutated, there will be less cell corpses, which means cells that are supposed to die, do not die. Autophagy is necessary for cell death in this situation. In normal development of the ventral cord neurons in C. elegans, the neuroblasts normally divide to form many cells that will develop the ventral cord neurons. Six of the Pn.aap cells will generate precursor cells P3-P8 which will turn into ventral cord motor neurons, which will then generate an additional 10 cells that will undergo programmed cell death. When both CED-3 and CED-4 genes are mutated in the worms, 6 of those additional 10 cells that are supposed to undergo programmed cell death will survive, differentiate into other cells, and acquire the wrong cell fates. It was seen that autophagy mutants enhanced the continuation of the cells that acquired incorrect cell fates. But when autophagy genes normally functioned/ or were enhanced, those cells underwent programmed cell death and the ventral cord neurons developed normally.
Links related to the paper:
Autophagosome formation: core machinery and adaptations - How autophagy works
C. elegans Screen Identifies Autophagy Genes Specific to Multicellular Organisms - What are some autophagy genes
Autophagy genes function in apoptotic cell corpse clearance during C. elegans embryonic development. - More info on cell corpse clearance
Programmed Cell Death - More info on programmed cell death
This paper talks about how neurons that are spread anterior-posterior in C. elegans help with developing organs in the right place. The neurons 'work together' with Wnt signaling to make the correct morphology of organs. Specifically, this paper looked for mutations that affected vulval formation and tissue placement as it relates to growth factor signaling. One specific mutation of the vab-8 gene affected vulval placement while the gene is mostly known for neuron migration and outgrowth. From this, they studied the neuronal mechanism that refined Wnt signaling to produce vulva in the correct position.
It is known that Wnt signaling plays a major role in organ development (vulva formation as an example) however the vast diversity of development in organisms that use Wnt signaling is huge compared to the limited signaling from growth factors. Additionally, there is relatively little information about gradients and patterns of signaling proteins in developing organisms.
When neurons spreading posteriorly in C. elegans were shortened, normal mid-body formation of the vulva were disrupted and produced further posterior in the organism. These findings tell us that neuron evolution, specifically in C. elegans, has lead to an expansion of function and use of Wnt signaling in body formation.
Links related to the paper:
More about neurons in C. elegans
More about C. elegans body plan