Therapeutic Success in Hematologic Malignancy - Assignment Example

Question 1: a. Statistics have shown the approved drugs incremental improvements in therapeutic success compared with single-agent chemotherapeutics (Uchida, 2001). In as much, though Ab drugs has shown successful trend of targeting antigens with ‘favourable differential expression profiles’, it has not succeeded on clinical trials and the reason attributable to this is insufficient demonstrable efficacy. Additionally, mAbs have not fulfilled the possibilities inherent in the view of Ehrlich. The issue includes identifying the best antigenic targets of therapeutic value with which to raise mAbs. This makes useful fragments of mAbs which is able to be produced by cancerous tumors attacking toxic payloads, like as immunotoxins or radioisotopes, to the mAbs as animal antibodies have been documented not to be as effective as human in recruiting the other cells of the immune systems that can complete their therapeutic function. Another major hurdle has been related to that of antisera therapy—especially when animal mAbs has been administered in multiple doses. In such cases, Uchida (2001) has shown that patient almost invariably raises an immune response to the mAbs which may in turn cause attenuation of biological actions and symptoms similar to serum sickness (190 words). b. There are processes of expressing mAbs from hybridoma technology that can humanize antibodies. The approach will be possible due to segmented structure of the antibody molecule which allow for functional domains carrying antigen-binding or functions of the effector to be exchanged. The first step is to get fully human and fully mouse antibodies then construct a chimeric antibody by also coupling the antigen-binding variable domains of the animal to human constant domains. The next step is to express the recombinant, engineered antibodies in myeloma cells. On the other hand, it is also possible at this stage to attach a mouse single chain Fv (scFv) with or to the CH3 domain of human IgG1. Such attachment is done using a redesigned human IgG1 hinge region that produces a bivalent partial chimetric antibody that breaks the hurdle identified. The reason to produce a chimeric antibody is the choice of human constant regions that has the ability to be provided as isotope relevant to the desired biological functions such as IgG3 and gG1 which are subtypes that are most effective for complementing and cell-mediated lysis-triggering effector which cascades whereas IgG4 and IgG2 are regarded for target neutralization with the end result being CDR-grafted. (201 words) c. Before the description of the test, it is worth noting that humanised anti-CD20 mAb binds just as well to CD20 as ibritumomab since Greg Winter (Uchida, 2001) has shown that only the antigen-binding site (human antibody) needed to be replaced by bringing the antigen-binding site (rodent antibody). The first test as suggested by Urashima (1997) is to use human acceptor V as long as it can show closest similarity to their mouse donor V regions. This approach is called ‘homology matching or best fit’ (Karp, 2001; Senderowicz, 2000). While doing the test, variations on the homology matching should consider the extent of sequence similarity (either the different human antibodies or the individual frameworks between the CDRs – chosen from either single or the whole V region) and matching lengths of CDRs existing between human V regions and the mouse. In doing this, consensus sequence can be given selection in this case (fixed framework) regardless of sequence similarity to the region V of the mouse applying the knowledge that the most abundant sub-groups of human are VH sub-group iii for the VL sub-group I for the kappa light chain and heavy chain. (191 words) d. i. Ab-dependent cell-mediated cytotoxicity (ADCC) ii. Ab-dependent cell-mediated phagocytosis (ADCP) Beginning with ADCC and ADCP, they are IgG class of Abs and thus governed by engaging the Fc region and this region has a family of receptors known as Fc_ receptors (FcyRs). However, ADCC and ADCP are different with regard to humans (Senderowicz, 2000). As protein family, they include Fc_RI (CD64); Fc_RII (CD32), which is also compost of isoforms such as FcyRIIb, FcyRIIa and FcyRIIc; and CD16 (FcyRIII) which include isoforms FcyRIIIb and FcyRIIIa. Senderowicz (2000) explains that FcyRs can be expressed a different immune cells as well as formation of the FcyR/Fc compex recruits these cells to areas or sites of bound antigen. This typically results in signaling and immune responses like release of inflammation mediators, endocytosis, B cell activation, cytotoxic attack and phagocytosis. Finally, FcyRs have the ability to bind the same region on IgG Fc, yet with differing low (FcyRII and FcyRIII) affinities and with differing high (FcyRI) (162 words). Question 2: Patients with multiple myeloma (MM) are categorized to be having the most common hematologic malignancy, perpetually fatal.1 Therefore the quest for therapeutic modalities and novel agents in MM has become critical. This is why the introduction of IMiDs like pomalidomide and lenalidomide has gained momentum. Beginning with Thalidomide (α -N-phthalimido-glutarimide) it had anti-angiogenic as well as T-cell co-stimulatory.2 Accordingly, in refractory and relapsed MM, thalidomide managed to produce response rates that were approximated to be 30% as a single agent.3 In a new set of diagnosis patients, the achievement of response rate with thalidomide was 40% alone and when combined with dexamethasone it was 75%. Therefore with lenalidomide, it needs to be established that IMiDs comprises of unique but orally bioavailable agents that have refinement using thalidomide as structural template. Therefore the process of modifying thalidomide structure as one removes carbonyl present on the ring forms lenalidomide. These IMiDs have been designed to promote immunomodulatory as well as anticancer properties of thalidomide thus having fewer side effects. It is from this perspective that scholars have been documented on mechanisms by which IMiDs has anti-cancer functions.4 a. Anti-Angiogenic Activity As a mechanism, anti-angiogenic activity is one of the proposed anti-cancer functions of IMiDs. This is the development of new blood vessels in human body. When dealing with cancerous patients, the development of new blood cells as the capability of nurturing the growth as well as metastasis of tumors as well as tumor cells in that order. In this connection, IMiDs and thalidomide has been documented to have some properties of anti-angiogenic that are not dependent of the immunomodulatory effects.5 Through the process or activity, it is believed that it plays a role in the apparent efficacy as witnessed with a number of cancers. To give a case study, with the rat aorta assay, it was realized that IMiDs were 2 to 3 times more potent when it comes to their anti-angiogenic activity when comparison was made with thalidomide. b. Pro-Apoptotic Agents The first demonstration to this mechanism was by Hideshina et al. (2001) who showed that thalidomide and its respective analogues could induce tumor cell apoptosis, when evidenced by the induction of p21 and linked G1 growth arrest or increased sub-G1 cells.6 In the process, it was found that IMiDs was able to inhibit the proliferation of chemoresistant MM cells by about 20% to 38% and at the same time that of dexamethasone-resistant MM cells by about 50%.7 The research also found that when caspase-8 activation was enhanced, it increased sensitivity to Fas induction while at the same time reducing expression of cellular inhibitor of apoptosis protein-2. c. T Cell Costimulators Imminumodulatory and thalidomide drugs can be able to induce drugs of MM patients’ interleukin-2 T cells and interferon-gamma production in vitro. However, there were not cytotoxic to MM cells.8 The report further indicates that these drugs had the ability of enhancing natural killer cell-mediated lysis of autologous tumor cells. Additionally, it has been found that when there is an increase in IL2 as well as IFN-gamma the CD40L expression on T cells is unregulated especially when the research added IMiDs to anti-CD3 stimulated T Cells.9 In as much as some studies have shown greater costimulatory impacts on the CD8+ T cell subset when such is compared to the CD4+ T cell subset that has also been observed in another study, there has been other studies that have shown similar co-stimulation for CD8+ and CD4+ T lymphocytes that could be correlated with TNFR2 inhibition.10 d. IMiDs as Immunomodulators The potent inhibition as far as TNF-alpha and the use of IMiDs was given a demonstration in LPS-induced PBMCs both vivo and vitro.11 The report has indicated that compared to the parent drug thalidomide, the analogues was able to inhibit TNF-alpha better and even did so when it came to inhibiting IL12 production and LPS-induced monocyte IL1-beta12 This process also enhances the production of interleukin 10 (IL-10). The report further indicates that IMiDs was only able to partially act as inhibitor effect on IL-6. When it was tested in vivo, the amide analogues were able to protect 80% of LPS-treated mice against death from endotoxin-induced shock.13 (801 words) Question 3: This analysis recognizes that immunodominant epitope of insulin in Type 1Diabetes is hypothetical case only offers laboratory tests that have been conducted before. Considering mouse stains, strain from non-obese diabetes (NOD) can spontaneously develop autoimmune diabetes along with the development of insulin autoantibodies.14 The research also identified that when immunization is only done H-2d and ignoring H-2b mice with insulin B chain amino acids 9 to 23 peptide is likely to result in insulin autoantibodies.15 Additionally, NOD mice have the ability to show cellular autoimmunity to insulin. When T cells are directly isolated from panacreatic islets of NOD mice, it is found that significant population of CD4 T cell clones could establish after being stimulated with islets as antigen was reacted with insulin and of the T cell clones reacting with insulin. About 90% was able react with insulin peptide B: 9-23.16 The explanation that was given was that the clones had the ability of transferring diabetes into immunocompromised NOD. As already noted, this analysis works on the basis of a possible scenario. Therefore the question of insulin as a primary autoantigen should be tested. The detection of insulin reactive T cells which are present in younger NOD mice and the development of insulin autoantibodies which often precede other autoantibodies in human being have the contribution to the hypothesis that insulin can be essential for the development of type 1 diabetes. Conversely, there are two preproinsulin genes which are ins1 and ins2 and knockout of the ins2 gene which in turn accelerates diabetes of the NOD mouse.17 It is from the argument above that putative epitopes of insulin/proinsulin have been developed. Also the analysis above has shown that insulin peptide B: 9-23 could be a primary autoantigen while referring to the NOD mouse and since amino acid sequence is identical in both humans and mice, B: 9-23 could a significant role in man. Alleva and coworkers generated insulin B: 9-23 reactive cell lines that were found from PBMCs by short time stimulation with peptide and IL-2 from recent-onset type 1 diabetic individual. However, they did not find peptide reactivity in controls.18 Following the study where T cell epitope mapping of insulin by using serial overlapping peptides in Japanese, it was found that all epitopes that can be recognized by T cells were identified in the B- chain of insulin. Additionally, it was noted that B4–18, B12–26 and B9–23 were identified in some patients at the same time frequent epitope found in B1–15 and B11–25 regions and B10–24 region.19 Therefore it is worth concluding that the insulin B: 10-18 epitope is a target of autoreactive CD8T cells with very high binding affinity for HLA-A2. Panels of 8- to 11-mer peptide within proinsulin region 28-64 were recognized by PBMCs. Four proinsulin peptides (41–50, 42–51, 44–51 and 49-57) were recognized by a high percentage of HLA-A1 and -A3; HLA-A1, -A2, -B8, and -B18; HLA-A1 and -B8; and HLA-B8 diabetic patients, respectively. Conversely, proinsulin 51–61peptides and 49–57 that was located within a region overlapping the B chain and C peptide. Neither 51–61peptides nor 49–57 were recognized by PBMCs from insulin-treated type 2 diabetes patients or control individuals. To consider in this case is that T cells recognize insulin B10-18 differently in type 1A diabetes both at disease onset as well as after longer disease duration, however, not in nondiabetic controls and type 2 diabetes. It remains that immunodominant epitope of insulin is a major component of the pathogenesis of type 1 diabetes. In the NOD model has it has been considered, it can be hypothesized that recognition of the insulin B: 9-23 peptide by a non-stringent can conserve Jalpha and Valpha T cell receptor combination. This enhances the chances of anti-insulin autoimmunity owing to NOD’s penchant for autoimmunity.20 This analysis has considered mouse model but again human diabetes type 1 may of course become more heterogeneous compared to the mouse model. Based on the discussion above, it can be concluded that it is possible to predict type 1A diabetes in human being and prevent it in animal model. (800 words) Question 4: a. The tribe in the remote area of New Guinea is exhibiting a rare case but the explanation can be tied to the process of genetic recombination that takes place in the early stages of immunoglobin (Ig) as well as T cell receptors production of their immune system. Being a tribe in isolation VL and VH multigene families can evolve in the same fashion. Additionally, the level of diversity among the VL and VH genes in every member of the tribe is connected to the mechanism of generation of antibody variety. From this assessment and basing on the case of the tribe, the rearrangement of DNA of immunoglobulin diversity, variable, and joining-segment gene can be the main source in this case, of antibody diversity. As been noted earlier, the pattern of evolution of VL and VH multigene families is consistent with the birth and death model of evolution. Another possible reason in this case it is one of Diverse, Variable and Joining gene V(D)J in the lymphosytes and since it does so randomly when choosing different genes, there is a possibility that there is diverse encoding of proteins to match antigen coming from bacteria, parasites, viruses, pollens and dysfunctional cells like tumor. b. When assessing the activation of T cells, before looking conditionalities under which they are done, it is necessary to consider three different types of signals. The first signal is the antigen-specific that are derived from the interaction of a specific peptide. Therefore based on this signal, the process of engaging the T cell receptor with its peptide antigen is necessary for activating a naïve T cells. However it needs to be noted that if there is co-receptor---CD4 or even CD8 is also lighted then this does not on its own, make stimulation to the T cells to fully proliferate and differentiates into two other signals. These other signals in this cases become the co-stimulatory which have the ability to stimulate the survival and expansion of the T cells and the third signal being the ones that is involved in directing T cells through the process of differentiation where such differentiation further leads to different subsets of effector T cells. In such process, molecules are regarded as the best-characterised co-stimulators molecules that can deliver signal 2. Basically, these are homodimeric a member of the immunoglobulin superfamily that are located exclusively on the surfaces of cells and dendric cells being one of such and their responsibility is stimulate naïve T cells proliferation. As one of the condition, their role while stimulating is to transfer fibroblast that has the ability to express a T cell ligand with gene that encode B7 molecules and show that the fibroblasts are able to stimulate the clonal expansion of T cells. While mentioning the receptor for B7 molecules on the T cells the one in this case is the CD28. Finally, when CD28 is ligated by B7 anti-CD28 antibodies or by B7 molecules then such become necessary for the optimal clonal expansion of T cells. c. It is important to note that T cells can be categorized into two further large classes. The first is the one carrying the co-receptor CD8 on its surface and the other is having the responsibility of bearing the co-receptor CD4. CD8 can differentiate to become CD8 cytotoxic T cells (referred to as cytotoxic lymphocytes). When differentiation takes places, CD8 cytotoxic T cells or cytotoxic lymphocytes defend against intracellular pathogens, (virus). As Senderowicz (2000) notes, virus infected cells will display fragments of viral protein in form of peptide in this case MHC class 1 complexes located on their surface. This is in turn will be recognized by cytotoxic T lymphocytes. It is worth noting however that since the effector actions of these cells can be very destructive, CD8 T cells require, to some extent co-stimulatory activity so as to drive them to become activated effector cells rather than being naïve CD4 T cells. It has been noted through research that in the majority of viral infections, CD8 T-cells activation need help from CD4 effector T cells. On the other hand, CD4 T cells and CD8 T-cells can differentiate into a number of subsets and one of such is the TH1 which help in controlling bacteria setting up intravesicular infections in macrophages like mycobacteria that are responsible for leprosy and tuberculosis. On the other hand, TH2 control infections caused by parasites. Lastly, there is TH17 whose main role is to protect against extracellular fungi and bacteria not to mention CD4 T cells that provide help to B cells for the production of antibody. A point to note is that it is THH cells but not TH1 or TH2 that is the effector T cells that can be attributed with the role of providing B-cells with help for high-affinity production of antibody. (802 words) References Karp, J. E. et al. Current status of clinical trials of farnesyltransferase inhibitors. Curr. Opin. Oncol. 13, 470–476 (2001). Senderowicz, A. M. Small molecule modulators of cyclindependent kinases for cancer therapy. Oncogene 19, 6600–6606 (2000). Uchida, T. et al. Hypermethylation of p16INK4A gene promoter during the progression of plasma cell dyscrasia. Leukemia 15, 157–165 (2001). Urashima, M. et al. Characterization of p16 (INK4A) expression in multiple myeloma and plasma cell leukaemia. Clin. Cancer Res. 3, 2173–2179 (1997). Dear customer, Read More