The purpose of this research study is to determine the amount of a protein named thymidine synthase that is being made by cancer and to develop laboratory models called PDX (patient derived xenografts) to learn more about SCLC (small cell lung cancer) and to begin testing new treatments.

Small cell lung cancer (SCLC) is a highly lethal malignancy that is not treatable with targeted therapies and that does not respond long-term to treatment with cytotoxic chemotherapy1. One distinguishing molecular characteristic of SCLC is very high expression levels of thymidylate synthase (TS). TS plays an important role in de novo nucleotide biosynthesis and the very high TS levels expressed in SCLC cells indicate that these cells require the de novo nucleotide biosynthetic pathway to proliferate. Thus, complete TS inhibition could result in highly favorable outcomes in SCLC patients. TS inhibitors have been evaluated in SCLC clinical trials and have anti-tumoral activity when combined with a second chemotherapeutic agent. However, treatment with TS inhibitors has not been shown to surpass other combination chemotherapy regimens. An important point regarding these clinical studies is that TS activity levels were not monitored as an endpoint of drug response, thus it is not known whether TS activity was efficiently inhibited.Investigators predict that complete TS inhibition will result in favorable outcomes.

With support from Wake Innovations, Investigators are developing a novel fluoropyrimidine polymer, CF10, which strongly inhibits TS. CF10 is a second generation fluoropyrimidine polymer. The first generation polymer, F10, showed excellent anti-cancer activity in animal models of acute myeloid leukemia, glioblastoma, and prostate cancer. CF10 is designed to have improved tumor penetration and better in vivo stability than F10. Investigators hypothesize that CF10 will be highly effective for treating SCLC both as a single agent and in combination with TS inhibitors that target alternative sites of the TS enzyme.

After establishing CF10 has activity as a single agent and in combination with folate-based TS inhibitors (e.g. pemetrexed) in SCLC cell lines and xenograft models, Investigators will test CF10 in patient-derived xenograft (PDX) models and in organoids derived from SCLC patient samples. Investigators will develop PDX models of SCLC and SCLC organoids using transbronchial fine needle aspiration (FNA) from SCLC patients at Baptist/WFBCCC collected by co-I's Bellinger, Dotson, and Thomas. Non-malignant cells will be collected using a brush biopsy to enable comparison of malignant and non-malignant tissue from the same patient with regard to mechanistic endpoints.

Inclusion Criteria:

• Patients undergoing a diagnostic FNA by the following diagnostic modalities utilizing FNA: Endobronchial Ultrasound Guided Transbronchial Needle Aspiration (EBUS- TBNA) or conventional transbronchial FNA.
• Patients must have radiographic evidence for presumed lung cancer or have a previously diagnosed SCLC with clinical evidence of recurrence. Patients undergoing FNA of potential SCLC metastates to lymph nodes are also included (e.g., patients with abnormal mediastinal lymphadenopathy). FNA biopsies from separate locations in the same patient will be considered separate specimens.
• Age >18 years. Used to define adult age that can independently provide consent.
• Ability to understand and the willingness to sign a written informed consent document.

Exclusion Criteria:

• Patients whose FNA biopsy is unable to provide classification by pathology or is non-diagnostic.

• Women and men of all races and ethnicity who meet the above-described eligibility criteria are eligible for this trial.
• The study consent form will also be provided in Spanish for Spanish-speaking participants.