Front-line paclitaxel and topotecan chemotherapy in advanced or metastatic non-small-cell lung cancer: a phase II trial

Mitochondria of T Lymphocytes Promote Anti-Pulmonary Tumor Immune Response

Background

B-cell lymphoma 2 (Bcl-2), a protein involved in apoptosis, has been proven to have carcinogenic potential and is well documented. With the recent advancement in optical technology, it has become possible to observe subcellular organelles such as mitochondria in real-time without the need for staining. Consequently, we have examined the movement of mitochondria in cancer cells, correlating it with the regulation of Bcl-2.

Methods

Using a tomographic microscope, which can detect the internal structure of cells, we observed lung tumor cells. Cells were exposed to a laser beam (λ = 520 nm) inclined at 45°, and holographic images were recorded up to a depth of 30 µm of reconstruction.

Results

Intriguingly, lung tumor cells rapidly expelled mitochondria upon the attachment of Bcl-2 or B-cell lymphoma extra-large (Bcl-xL) inhibitors. On the other hand, we observed that tumor cells hijack mitochondria from T cells. The hijacked mitochondria were not immediately linked to tumor cell death, but they played a role in assisting granzyme B-induced tumor cell death. Due to lower levels of Bcl-2 and Bcl-xL on the mitochondria of T cells compared to lung tumor cells, immune cells depleted of Bcl-2 and Bcl-xL were co-cultured with the tumor cells.

Conclusions

As a result, a more effective tumor cell death induced by granzyme B was observed. Additionally, further enhanced anticancer immune response was observed in vivo. Together, we show that modified mitochondria of T cells can provide potential novel strategies towards tumor cell death.

Establishment and Characterization of a Topotecan Resistant Non-small Cell Lung Cancer NCI-H460/TPT10 Cell Line

While topotecan (TPT) is a first- and second-line chemotherapeutic drug in treating lung cancer, the development of drug resistance in tumors still reserves as a major obstacle to chemotherapeutic success. Therefore, a better understanding of the mechanisms of topotecan resistance is critical. In this study, the first topotecan-resistant human non-small cell lung cancer (NSCLC) cell line, termed NCI-H460/TPT10, was established from the parental NCI-H460 cell line. NCI-H460/TPT10 cells exhibited a 394.7-fold resistance to TPT, and cross-resistance to SN-38, mitoxantrone, and doxorubicin, compared to parental NCI-H460 cells. Overexpression of ABCG2 localized on the cell membrane, but not ABCB1 or ABCC1, was found in NCI-H460/TPT10 cells, indicating that ABCG2 was likely to be involved in topotecan-resistance. This was confirmed by the abolishment of drug resistance in NCI-H460/TPT10 cells after ABCG2 knockout. Moreover, the involvement of functional ABCG2 as a drug efflux pump conferring multidrug resistance (MDR) was indicated by low intracellular accumulation of TPT in NCI-H460/TPT10 cells, and the reversal effects by ABCG2 inhibitor Ko143. The NCI-H460/TPT10 cell line and its parental cell line can be useful for drug screening and developing targeted strategies to overcome ABCG2-mediated MDR in NSCLC.

Role of Topotecan in Non-Small Cell Lung Cancer: A Review of Literature

Topotecan (TPT), a chemotherapeutic agent, is a topoisomerase-I inhibitor. Topoisomerase-I is a nuclear enzyme that relieves torsion strain in DNA by opening single strand breaks which helps in DNA replication. TPT inhibits this enzyme, thus preventing DNA replication and causes cell death. TPT has demonstrated to have broad spectrum of antitumor activity in tumors like cervical, ovarian, endometrial and small cell lung cancers (SCLCs). The intravenous (IV) formulation of the drug is currently approved by the US Food and Drug Administration for the treatment of patients with SCLC and ovarian cancer at a dose of 1.5 mg/m² administered daily for five consecutive days, with treatment cycles repeated every 3 weeks. TPT has shown some promising activity in the treatment of non-small cell lung cancer (NSCLC) with favorable side effect profile. Several clinical trials have been conducted with TPT in either IV or oral formulation for the treatment of NSCLC as a first or second-line treatment. Here we reviewed all the clinical trials done with TPT to date in the treatment of NSCLC both as a single-agent and combination therapy.

The role of the mitochondria in mediating cytotoxicity of anti-cancer therapies

Optimal cytotoxic anticancer therapy, at the cellular level, requires effective and selective induction of cell death to achieve a net reduction of biomass of malignant tissues. Standard cytotoxic chemotherapeutics have been developed based on the observations that mitotically active cancer cells are more susceptible than quiescent normal cells to chromosomal, microtubular or metabolic poisons. More recent development of molecularly targeted drugs for cancer focuses on exploiting biological differentials between normal and transformed cells for selective eradication of cancers. The common thread of "standard" and "novel" cytotoxic drugs is their ability to activate the apoptosis-inducing machinery mediated by mitochondria, also known as the intrinsic death signaling cascade. The aim of this article is to provide an overview of the role of the mitochondria, an energy-generating organelle essential for life, in mediating death when properly activated by cytotoxic stresses.